Electric boat conversion

2010-07-17T03:21:00.000-07:00

This blog describes most of the elements of our successful conversion of NB Worcester to electric drive, using an on-board diesel generator to re-charge the drive batteries, with solar cells for final "top-up" and battery maintenance.

Since I have not found a way of re-arranging the postings in a sensible order, may I suggest you use the "labels" on the right to select which post(s) you wish to read - &/or to read them in a "sensible" order (A - S!) rather than reading them in archive order! (When you get to the bottom of a posting, click "home" to return to this page and the list of postings.)

I do apologise that the blog still contains typos despite careful editing... and I have deliberately chosen to often describe things at length and/or chattily since so often our success has come from the everyday detail!

I should perhaps admit that this conversion has proved a total triumph for our purposes - it really, seriously, works extremely well and we have now tested it in time and - thanks to amazingly adverse weather - in river conditions where we would not normally have expected to boat.. and it has performed entirely adequately.

Should you wish for further info, please leave comments on this page ....

Modfications and report July 2010

2010-07-16T14:12:00.000-07:00

In the first place, to report that the conversion is still working extremely well and as previously described, with no major snags at all arising and absolutely zero major maintenance costs (although the generator is overdue for a routine service!)

As a non-conversion comment, for a recent trip our fridge seemed to be performing poorly - now corrected by:

(1) Inverting the whole thing ("off"!) for about 5 minutes when

(2) I discovered one of the fans (see elsewhere) had become dislodged - but the effect of this being wrong not thought to be very significant

(3) I discovered a food label stuck to the door seal at the bottom - which might have been quite significant to the poorer performance, - impossible to tell.

The inversion "cure" for this kind of thermal fridge is apparently well known - especially for a unit used as rarely as ours. Anyway, for immediate test, the thing now froze a "bag" of ice cubes reasonably rapidly, so I think a cure was effected.

It should be noted that I have rewired so that ALL "12V" functions, domestic and for the genrator, etc., except for the actual generator start motor and its solenoid, now come actually at 14.7V via a 72:14.7 DC:DC converter powered by the drive battery stack. The 14.7V output was chosen as being ideal for recharging a single Odyssey -type "12V" battery unit.

The effect has been totally satisfactory although completely non-conventional. For one thing, this means that domestic power is actually from a 600 A-hr reserve and so even extended use of our power-hungry TV causes minimal discharge of the drive battery stack. For another, because the actual domestic supply voltage is 14.7V, all losses due to cable lengths down the boat are not a problem - in particular, a "12V (d.c.): 240V (a.c.)" invertor at the bow end (for the TV) never cuts out for insufficient supply voltage (as it used-to as the domestic conventional battery ran down - way before this was actually "flat" but losses down the cable down the cabin meant voltage at the inverter fairly rapidly fell below 12V.)

It should be noted that the "72:14.7" converter produces 14.7V output for an input around 60V and up to 90V - so the domestic and ancilliary power is at fixed voltage even if the voltage on the drive battery stack varies a lot (as when in use powering the boat.) So not only is domestic power coming from a "huge" store of 600 A-hr, its voltage doesn't change for using the store!

The generator start motor (and its solenoid) (and automatic bilge "on") are powered directly from the "1st" battery in the drive chain - a method I was warned would lead to all sorts of recharging problems. However, these warnings have proved totally invalid - I have meters measuring the charge-state (via voltage) of the "first" battery and the next in the chain and, fascinatingly enough, although the "first" may show slight relative deficit after several generator starts, the levels categorically self-equilibrate over time for (partially) discharging and recharging the whole stack in using the stack to drive the boat and recharging it (at "72V", via the generator.)

I do have a switch fitted to recharge the "first" battery "extra" from the 72:14.7 converter but in fact the time one needs to use this to rebalance the charge levels immediatly after a start is very short... and unecessary - because if you leave well alone, the recharge levels re-balance over time. Indeed, if you use this extra re-charge method for too long, the "first" battery ends up more recharged than the rest and it takes some time for the system to re-balance again!

The fact this asymmetric use of the battery stack self-balances - although not a commonly known fact - is not really so strange if one remembers that many rechargable battery units are in fact made of a series "stack" of cells and if they didn't self-equibrate then they wouldn't work very well at all because there will always be a "less-charged" cell... and if it became more discharged for a recharging process the whole stack would rapidly fail with this weak cell becoming worse and worse... but this simply doesn't happen! SO, the fact it doesn't reveals that a series set of cells will tend to self-equilibrate... and my rewiring and usage shows this is true, as well!

Note, mind you, only for small differences - but the amount of "extra" discharge to start the generator is tiny compared to the bulk supply of "12V" electricity which comes from the whole stack.

As a bit of theory, I realise this self-equilibration is against conventional circuit rules, but it should be remembered that current flows are not "smooth" steady flows but consist of ions belting around (due to thermal movement as well as local micro electric forces) oscillating both "backwards" as well as "forwards" with a tendency to "forwards" - the flow is actually an oscilliatory wave-like process, which allows plenty of mechanism for extra re-charge of a less-recharged cell.

The rewiring also means that all our power comes from the Odyssey units and we have no auxilliary units. This has the added huge advantage that this type of unit simply does not loose charge if left unattended (but near full recharge) even for extended periods of time - our solar cells, in addition, maximise apparently zero loss of performance over what is now 3 years. Nor do such units suddenly "go flat" - not just "what the leaflet says" but I think we've now observed this to be fact - and completely contrary to the problems I had when our conventional domestic battery went flat in cold weather - during which meter readings revealed both it and the conventional start battery needed constant checking and re-charging. Such concerns are now a thing of the past as a result of the rewiring!! (Although, madly enough, I've retained the actual old batteries to (a) keep the ballasting of the boat the same and (b) use two of their terminals (otherwise completely disconnected) as physical points to attach my re-wiring rather than have to make new heavy-duty-wiring connection points!)

I've also recently fitted a switch and a bit of electronics to make the generator start (and stop) a "one touch" operation. The control is simply a sprung centre-off micro-switch.

For the first start of the day, one still has to turn the generator "ON" using the Fischer-Panda "on" button and then the pre-heat button for about 6 seconds. But otherwise, (and after this for the first start of the day,) for "on" you simply "spring" the switch upwards for "on/start" which:

(1) turns the generator circuits on (simply mimics for 3 seconds that you've pressed the "on" switch - if you have already as above, doesn't matter!)

(2) starts the generator (simply mimics the "start" button for 3 seconds - the Fischer-Panda control panel cuts the actual start motor once the motor fires)

(3) "overrides" any fault conditions detected by the Fischer-Panda system (which prevent restart) - in particular "overheat" - for 100 seconds. This may sound strange, but the problem is that once the generator has been in use for any length of time, when it is stopped, its cooling also stops. As a result heat spreads within the unit following the stop and subsequently the overheat detector registers an "overheat" fault condition - which precludes starting the generator... when what is needed is to start the generator to pump the water to cool it!!

I used to set this overrride via a manual switch if the "overheat" indicator had come on when turning the generator on... but all quite a fuss because, not least, the indicator is very difficult to see in daylight! Further, the switch mustn't be on unless the generator circuitry is "on" or the Fischer-Panda system is so wired its relevant relay has a conflicting signal and buzzes... and the switch mustn't be on when stopping the generator or... it won't stop! Now, the override may not be necessary, but it doesn't hurt to apply it (once the generator is in the "on" state.) And if all is well, the system will cool within 20/30 seconds for restarting, so to apply the override automatically for definitely (but not much) longer than this means it will (almost) certainly restart and cool itself appropriately - I chose 100 seconds because I didn't want the override possibly turning off too soon... but if "overheat" was still registering after 100 seconds then the motor should certainly be switched off - and still would be!

(4) "tells" the VCS circuit to speed up the generator to max allowable (usually max output unless the batteries are very near full recharge - the VCS controls the speed to be max with the limit that the charging voltage isn't greater than around (settable) 88.5 Volts or so.)

So the one brief "flick" of the switch does everything to start the generator and speed it up suitably - I do love that one is thereby starting a 6kW generator with momentary application of a microswitch!

For stopping, a "flick" the other way:

(1) Mimics the stop button on the control panel and stops the generator and

(2) "tells" the VCS to send "slow down" pulses to the generator for 15 seconds, so the generator starts at minimum speed for the next restart.

This all seems to work totally satisfactorily.

However, it highlights a discussion I've had with several people - many favour the idea that the generator has completely automated start and stop to maintain the battery charge level but I find the arguments flawed on several counts.

(1) For a start, this kind of automated restart assumes you only start the generator when the batteries need it. But normally one never runs them anything like that low, you recharge whenever convenient where the decision as to what is convenient has to be a human choice!

(2) Operating as in (1), the batteries are often only about 20% discharged - and small % discharges increase battery life vastly compared to running them right down, even if they can survive this!

(3) Automated switch "off" would be based on battery plate voltage according to any system I've come across. But there are two problems with this:

(a) if one is stationary and aiming for full recharge, you only achieve this for first the voltage getting to the maximum allowable and then continuing recharge at this voltage but with lesser current (the VCS does this atomatically - as the batteries come to full recharge the VCS maintains the (max) voltage across the batteries but slows the generator so the current falls) - switch-off should be determined by voltage at max. and recharge current of "low enough" value - indeed, it would be suitable to have automatic switch off for V = 88.5V (approx.) and recharge current about 20 Amps - but this is not the normal system and would only apply when stationary and doing final top-up - boating ordinarily the generator would never switch off!

(b) there are many times you want to choose to switch the generator off way before the conditions in (a) are true.

I simply can't see how one could have an automated recharge system that didn't require human intervention making choices impossible to automate. To be sure, you could automate for switch on (by choice) for, say, 20% discharge... but you still wouldn't want this to happen if you shouldn't be running a generator at that moment, e.g., in a river lock or at night! And you could, by choice, set the generator to turn off if you have "suitable" recharge... but how to measure that would be very tricky and you'd still need to set this by choice so you could also set "go for full recharge" at, say, the end of the day - in other words, you could automate conditions for automatic switch on and off but you'd need a set of options according to circumstances!

Personally, I think the most sensible thing is a "one touch" start and stop (as I've now made) with plenty of indicators to advise about choice....

(Again, there are so many non-automateable reasons for choice - to mention a drastic one, if you see debris in the water you want to switch the generator off at once to avoid a blockage! Mind you, with hind-sight, I think our "bad experience" (see other postings) with cooling water intake failing and a consequent bust impeller was probably NOT a blockage in the filter but that I had failed to check the vacuum seal after cleaning the filter... I'm pretty sure. In fact, my fault for not being fully aware what needed checking!!)

Overall, it remains clear that our system does NOT have fuel-consumption advantage over conventional diesel, but it DOES have:

(1) Zero engine maintenance - although the generator is now overdue for a routine service - after three YEARS!!!

(2) Slightly more max. power than conventional diesel, continuous

(3) Vastly greater (virtually silent) accelerative power allowing control you simply can't do with conventional diesel - in particular one can so easily apply brief touches of intense power to nudge the boat position as desired or hold it steady in a fixed position.

(4) reduced licence fee - the drive counts as electric.

Finally, thanks to my Waterways World article and this blog, I am now advising a firm called Motech Control Ltd. who are developing an "off the shelf" version of our system, where the electric motor unit is shortly to be available - I am due to swap this with our motor soon to compare performance!

Incidentally, as part of the preparation for this, we found propellor revs for our standard prop (17" x 12", diameter x depth/pitch) are:

Canal cruising speed (4 mph): 630 rpm
Upstream "Quiet river" cruising (6 mph): 755 rpm
Upstream "Code Yellow" river (6 mph): 885 rpm
Our max. revs: 1080 rpm.

Wiring modifications

2009-06-17T10:20:00.000-07:00

I have now carried out wiring modifications - mostly as outlined in entry "Q" - and been able to observe effects (all seems good!)

As a main outline, ALL domestic and ancilliary functions (except as below) are now powered by a 400W 72:14.7 (DC:DC, volts) converter from the drive battery stack. An output of 14.7V was selected because this is (said to be) the "ideal" recharging voltage for Odyssey -type batteries (our drive battery type.) The converter is powered from the stack of six drive batteries, turned on by the main "on" switch by the steering position. This does mean this must be "on" for any electrical activity (including lights, pumps, etc.)... but since you would be on the boat to use anything, this is all to the good! Note that we no longer use any batteries other than the drive batteries.

The only exceptions to this arrangement are that:
(1) the gen-set satrter motor and its solenoid are powered by the "first" of the drive batteries (in the stack) - call it 'A'.
(2) the bilge pump auto-switch-on is powered similarly. Not that for manual use, it is powered by the converter.

Note that this means (virtually) all 12V power comes from ALL the drive batteries - charge returned by running the generator.

I was advised/warned that the asymmetric extra use of 'A' would cause a minefield of problems. I myself assumed 'A' would need "extra" recharging and wired so that it can be recharged at 14.7V from the converter, at will, with a manual switch. The charge state of 'A' (in fact, just the voltage across its plates!) is metered (using the meter that previously measured the state of the 'start' battery) and the charge state of the "next battery up" (call it 'B') in the series chain of drive batteries is also metered, using the meter that previously measured the state of the 'domestic' battery - these meters are side by side (see "control panel" posting) so it is easy to compare battery states.

In fact it turns out that when 'A' and 'B' are in near-fully-recharged state the last 0.5V or so does not represent much charge, and one can see that 'A' reads lower after using it "extra" to start the generator. However, once 'A' and 'B' are used more heavily (driving the boat) the difference of state is not really measurable and over a cycle of use (20/30% discharge and recharge), 'A' ends up as much recharged as 'B' and doesn't need extra recharge - the batteries self-equilibrate.

In fact if one guestimates the amount of charge used for a start, this is less than 0.1 A-hr - less than 0.1% discharge, so it isn't crazy the re-charge self-equibrates - if unequal charge states of this kind of order didn't self-equilibrate, no rechargeable battery made of more than one cell would last long - the "weaker" (slightly less re-charged) cell (and there will be one) would quite rapidly become weaker and weaker - an unstable equilibrium effect - and the battery become useless quite rapidly. This doesn't happen (thank goodness!)

Simple current theory precludes a process of self-equilibration, but batteries aren't simple conductors! In fact the re-charging process will be (at low level) a wave-type process of currents (ions) overall flowing the one way, yes, but with back ripples, so there is certainly room for an unequal recharging process as the ions settle down for full re-charge state - and, waves or no, the current flowing in the more re-charged batteries will have less recharging effect than in the less-charged battery, so it can "catch up". OK, not exactly exactly but the last 0.1% really doesn't matter... and I only USE 0.1% to start the generator!

Even more to the point, the theory doesn't matter, simple observation is that 'A' and 'B' self-equilibrate over a cycle of use. It may be that 'A' will wear out slightly sooner although I doubt the effect would be really significant. If I detect signs that 'A' is "tireder" later on I will simply swap batteries so that which actual battery is 'A' is rotated. However, I won't bother to do this unless there are any signs 'A' is suffering!

Incidentally, at one point I switched 'A' to have extra recharge only to find it was now MORE recharged than 'B'... luckily this effect self-equilibrated for another cycle of charge and discharge!

Whilst rewiring to avoid the need for separate ancilliary batteries, I also "tidied up" some inconsistencies in the original system - for example, it was possible to start and run the generator (and therefore the boat, for as long as you liked) without having to turn on the key!!

I have now rationalised all this so that the key must be on to run/start the generator, or work the bilge pump manually or for the drive motor's cooling fan to operate (or work the horn, front light.) The boat cannot now, therefore, accidentally run down battery 'A' whilst you aren't there or aware of what you've set - unless the bilge pump switches automatically and jams "on". Ah well, in that (terribly unlikely) event I'd have to use my switch to bring 'A' back in line!

I incidentally used the now "spare" switch previously used to recharge the 'domestic' battery so one can choose to turn off the motor-cooling fan. This may sound silly - surely the fan must come on automatically if the drive motor is "too hot"?

Well, for a start this fan was only fitted to upgrade the motor from 10kW to 12kW. We never normally actually use more than 6kW except briefly - so the fan isn't really needed! However, possibly just as well to have it because air-flow around the motor is fairly restricted... but it isn't essential it is on every second if the motor is a bit hot. And, in fact, its (the fan's) noise is quite distracting if you are doing quiet manouevres. Even better, now we have the choice - yes, the fan might is possibly better run IF the motor is a bit warm and the noise isn't intrusive, but, if it is, you can switch it off.

My (home-made) VCS (the unit that controls generator speed and so output so the recharge voltage never goes over 88.2V) started playing up recently. Very startling because it had been so fail-safe reliable. It was an intermittent fault. Opening up the box I discovered a fine wire checking "common earth" between the 72V drive batteries and the previous 'start' battery had actually melted at some point... without going into every detail of my deductive process and discoveries, basically I have to be sure that as previously wired the 'start' battery had only had "common earth" with the drive batteries because the voltage across it and the 'domestic' battery were (very nearly) the same... which went wrong when the 'domestic' battery had a cell fail last Christmas!!!... all in all a whole lot of strange observations were explained - I hadn't realised the earths hadn't been wired solid from the outset!...

Clearly, with a wire melted, my circuit had suffered some most peculiar voltages... anyway, hopeless to try and trace which semiconductor was damaged, easier to re-build... which also caused me to re-think what I actually wanted. Thing is, the previous circuit, built to mimic the original Fischer-Panda unit (but better!) had a silly property it continually tried to accelerate the generator unless its voltage was in the 85.2 - 88.2 V "ideal" recharging range even though most of the time when boating (as opposed to topping up the batteries) the voltage is necessarily way below this. And when running the generator for that top up, yes, the unit cut the speed as the voltage rose but also "hunted" - put in a speed-up burst to be cut again - whereas the process you want is that the speed is cut when the voltage rises over the limit... generator runs at the slower speed, voltage on the batteries rises as they recharge more - takes as much as five minutes - then the generator needs to slow another (single) pulse.... not a continuous checking operation! There had also been a problem when the VCS did go funny that I had an indicator on the box, yes, but not showing on the control panel...

Anyway, so the whole system revamped. For one thing, you can see what the unit is "telling" the generator to do - a LED flashes green if it's telling the gen-set to speed up, red if telling it to slow down. And a three-position switch allows you to tell it to do the (hopefully) most sensible thing for different situations, as follows:
(1) "Down": the VCS issues "slow down" pulses indefinitely. This is used to slow the generator to minimum speed and zero output - if there's time this is the ideal thing to do before actually turning the generator off - run it about 5 minutes at this speed before actually turning it off and it cools enough not to "claim" to be too hot when you next go to restart it. (Where the illogic is that it needs to start to pump the water to cool itself!) See other postings about this rather annoying problem! Once the generator is at min. revs, you return the switch to "neutral" mid-position.
(2) "Up": the VCS issues "speed up"pulses idefinitely unless you are nearly recharged, in which case these stop when the voltage is over settable level - our case, about 87.5V. IF the voltage goes even higher (as it can since the system can take a time to adjust), the VCS issues a "slow down" signal. In normal usage this will never happen whilst cruising because the voltage never gets near 87.5V and this position is actually used to simply speed up the generator after starting to get max. output. Once this is achieved, you return the switch to mid "neutral" position.
(3) Mid position: I've called this "neutral, but in fact it isn't! In this position the VCS issues no pulses unless the voltage rises above 87.5V, in which case it issues a "slow down" pulse but never a speed-up pulse. This position ensures the voltage never goes above 87.5V for any cause. It's use is when you leave the generator running for final top-up - the generator will slow as recharge is obtained. You can leave the boat doing final top-up knowing it will "look after itself".

Please note, compared to people running their motors forever to "keep the batteries happy" our system only takes about 40 minutes for full recharge from quite severe discharge.

Not that anybody is reading this, but if you are and wonder why I bothered with eliminating auxilliary batteries to use only the drive batteries, there was good practical cause. I had minor havoc last winter when the 'domestic' battery refused to recharge - and I had to be careful to keep the 'start' battery recharged. The Odyssey - type batteries simply don't require this much attention, and they don't self-discharge if left reasonably fully recharged - not only as the sales people say but as observed fact, by me!

I also suddenly realised that if our domestic 12V power came from the drive battery stack the effective capacity was 600 A-hr - quite enormous. And simply no point in having a separate set of batteries for this if we didn't need them. By using the drive batteries directly, this also meant the power-source had this astonishing property you could recharge in amazingly short times... even if we slobbed all evening in front of our very cheap but current-eating TV it only means running the generator an extra ten minutes in the morning - not exactly a problem whilst you decide to have another cup of coffee or not.

Overall, be clear the system works. Very well.

Planned modifications 11/3/09

2009-03-11T13:11:00.000-07:00

Given the last posting and some other useful correspondence, I now plan to modify our conversion as follows:

A. Engine cooling:

As noted elsewhere in this blog, we have a problem that a blockage in the "live" cooling water intake can rapidy lead to overheating and damage to the impeller requiring prompt replacement (apart from clearing the blockage!)

However, the generator is actually cooled via a secondary, closed, water/anti-freeze circuit, itself cooled via a heat exchanger by the "live" water intake...

I intend to re-plumb so that this secondary water circuit is ALSO cooled via flow through our existing, disused, skin tank. In this case, (I hope!) if a blockage cuts the "live" intake, sufficient engine cooling will continue due to the flow through the skin tank.

The exhaust will cease being silenced so majorly - but this a minor inconvenience compared to not being able to run the generator and will only continue until it is convenient to clear the blockage and (if need be) replace the impeller - it takes the "emergency" element out of getting the "live" flow working after a fault.

What is not entirely clear at this stage is (a) whether our existing skin tank has sufficient cooling power to enable normal "flat out" running of the generator (but to have to limit max. revs during a fault condition would be far better than to have to stop running the generator altogether!) and (b) it seems the live water is also used to cool the diodes and the coils of the generator.... and I'm not sure how crucial this function is given that the diesel engine itself is kept "normally cool" - I would not expect either diodes or coils to heat up significantly even if delivering high current "by themselves" and that their cooling is included only because the whole generator unit is effectively thermally sealed (by the acoustic coccoon) from the outside world so in the long term all elements need active cooling for seriously long periods of use....

However, we never use the generator that long at a time, so if the motor itself is cooled when in use, I would suspect heating of the electrics would never be a problem. Equally, to risk trying my plan out would not be "fatal" since the F-P unit has cut-outs for the cases diodes or generator coils overheat.

If my plan works, note that the whole "risk" of blockage causing a major problem vanishes - although we will still want to operate the boat and the generator to avoid blockage since eventual repair would still be potentially necessary. But there is a big difference between being stuck with no re-charging source and about 4 hours' driving battery power left and being able to continue (without limit) until repair is convenient, merely with a louder exhaust and - possibly - with the generator running at reduced output!

B. Batteries in use and wiring:

I intend to rewire so that all power comes from our 'drive' battery stack.

One advantage of this is that all battery units will have the now-verified (from our experience) good properties of the Odyssey - type batteries we have for our drive. These are especially that they do not need re-charging attention if left longer periods (so long as they are left more-or less re-charged.) They also have the advantage of no "sudden collapse" in charge-holding properties if not maintained ideally.

For us, there are no other advantages of reduced weight, space or ballasting requirements since our conversion retained separate 'domestic' and 'start' batteries, but for others considering conversion to diesel-electric hybrid drive there could be considerable saving, both financial and of fitting/ballasting problems.

I feel it clearest to explain separately as regards the two functions I now intend to use our 'drive' batteries for:

1. Domestic needs:

In our case, and I would imagine for most boaters, domestic power requirement is never huge. I will be re-wiring so that all this power requirement in fact comes via a DC:DC 72:12 V converter from, therefore, ALL the drive batteries, but at 12V. In our case, we can use this up to a rate of 400W via our converter. What may not be obvious is that this means we have effectively 600 A-hr domestic capacity available - more than any system other than super-de-luxe I have heard of - where, yes, the truth is you would be unwise to use more than 300 A-hr before recharging - but in comparing figures our 600 A-hr as a statement is the same has having dedicated batteries of, say, 450 A-hr... the figure is the total, what you can actually sensibly use is in proportion.

For those might need domestic (temporary) currents greater than the 30A (or so) a 400W converter can provide, 'domestic' function should be wired as for 'start' function (see below) - and actually I will wire that way in any case since I see and for experiment have been able to find no disadvantage.

2. Start function:

This requires about 80A - but briefly - at 12V. One CAN actually obtain this kind of power (1kW) from all the drive batteries by using three converter units from the 72V drive batteries, but I can't see that this cost is necessary or sensible.

One can fairly easily wire so that one of the drive batteries - call it 'A' - provides all the power you'd ever need at 12V - but otherwise it comes via the converter from all the batteries. For the - and it would only ever be short-term - time 'A' is used more, the same converter can recharge the difference, from all the batteries. The exact control of this can be easily enough balanced. Mostly it simply means you recharge 'A' a bit although from my figures the extra use would hardly show...

I've not yet decided or worked out the best way to automate keeping all in balance - manual control is easy enough given suitable meters. Overall there is absolutely no theoretical problem except that 'A' had more discharge-recharge events....

But 'A' is only one of six identical units and the differences - I calculate - are small... so, maybe once a year rotate which battery is actually 'A'!

Not that anybody is reading this blog report!

Report and developments early 2009

2009-02-17T13:03:00.000-08:00

Writing 19/2/09 I can report that our conversion remains working (apparently) as well as ever as regards all main conversion elements - the drive and the drive batteries and the generator.

However, I have had some problems with the auxillary batteries. To explain, over winter I do not 'winterise' but simply check the state for everything from time to time, and guard against a freeze-up (when the weather requires this) by turning on the central heating boiler's pilot light and the water heater's pilot light if a mere 0 degrees C is forecast, actual central heating on (at frost setting) for a sub-zero forecast.

For a start, with the boat merely static on its mooring, recharging of the 'standard' 12V 'start' and 'domestic' batteries became rare... and I found that the meters revealed they were losing charge quite significantly when left alone for more than a couple of weeks - easy enough to rectify, simply hit the switches to recharge them from the 'drive' batteries via the 72:12 DC:DC converter.... for a while...

BUT, they did need more than a few minutes. As previously wired, to leave recharging switched on most of a day (to give healthy recharge) meant leaving the key switch on with the boat unattended, so I did a long overdue rewire so that the relays connecting the batteries (for re-charge) to the output of the converter was powered by that converter - which itself is powered when the main 72V ON switch by the steering position is on.

A long overdue rewire since previously the relays had been powered by 'key on' from the start battery... and when this had been near-drained for the drive motor cooling fan coming on thanks to water in its relay, the problem was the relay wouldn't go over because its power source was what you wanted to recharge!!!

I didn't have to do anything very drastic - there was still some battery power left, and a light tap on the relay case caused to to flick 'on'..... and recharge to take place.

Note that the drain on the 'drive' batteries caused by even six hours of recharging the auxillary batteries was easily replaced by running the generator for a mere ten minutes or so - and the 'drive' batteries showed absolutely no sign of losing charge unless I used them for this recharging process. (Mind you, they do have the 5W solar 'top up' 'on' all the time.)

However, a new problem arose when I started using the 'domestic' battery more for needing to run the full central heating - this battery provides the central heating pump. This, as expected, meant the 'domestic' battery definitely needed a recharge after a night's use. BUT, this started to fail... recharge appeared to be OK but a small further usage meant the 'domestic' battery voltage fell quite rapidly for even slight use.

The 'domestic' battery came new when the conversion was done, so I was rather surprised that I could only deduce it was 'failing' (as conventional lead-acids can) simply for being 'old' - compounded, perhaps, by the fact that it never had very regular re-charging. After further attempts to give it a decent recharge (via the converter) it became clear it certainly had something very wrong since it blew the converter (attempting a longer recharge!!)

For the time being, I managed to get an alternative converter to recharge the 'start' battery quite rapidly - and simply re-wired for this battery to also power the 'domestic' functions, for the time being - all of which has worked perfectly OK - except the the 'start' battery certainly needed a decent recharge after running the central heating pump all night.

However, this sequence of events shook me out of accepting the 'standard' arrangements we had - separate auxillary batteries for 'start' and 'domestic' function charged after use via the converter from the 'drive' batteries. And caused me to think harder...

For a start, what would happen if I left the converter 'on' powering the 'start'/'domestic' function? Answer, the 'start' battery became very thoroughly recharged whilst, in fact, the central heating pump had been driven by the 'drive' batteries (via the converter.) BUT, this was a drain on all six, so the drain per battery was really quite tiny.....

Consideration hit as another eureka moment. I didn't need a 'domestic' battery at all - all those functions could be powered via the converter from the 'drive' pack. The consumption involved I could easily calculate was relatively tiny compared to their normal use driving the boat - no question they would somehow accidentally become discharged in any significant way at all without me noticing - and easily recharged by the generator in very short times.

This thought caused me to wonder if I actually needed a separate 'start' battery - clearly our conventional one needed care to be sure to keep it OK by 'serious' recharging sessions... fom the 'drive' batteries which equally clearly didn't need much care... to be sure they would lose absolutely ideal plate voltage when left alone for two-three weeks... but only fractionally and a very short session of generator (around ten minutes) would have them right back to normal values.

I'm as cynical as anybody about sales' claims for devices, but I think I have seen for my own eyes that Odyssey -type batteries simply do not lose charge if left reasonably near full re-charge... whereas I've also seen that 'standard'-type batteries DO, and by contrast.

Overall, an idea was forming in my mind that (a) at least for all our domestic purposes, I might as well power them via a converter from the drive batteries and (b) we might be better to use one of the 'drive' batteries as our 'start' battery taking advantage of the superb Odyssey properties.

That's enough talk for this posting... I'll write another about the considerable trouble I took rethinking and testing as regards our battery requirements - end conclusion all-but verified is that if you have 'drive' batteries for a conversion, as we have, you do not need any separate/other batteries.

Electric boat conversion - the propellor

2008-09-06T09:07:00.000-07:00

This posting is rather a cheat since we merely kept the propellor on our boat as it was prior to the conversion(!), but I've included it since in researching our conversion I came across several articles and other comments concerned about the best propellor to use for an electric drive such as ours.

A common recommendation is to use a larger prop design with greater grip on the water. I personally cannot see the argument for this since the overall physics process is that you set a certain power input and then the electric motor will accelerate until "power out" = "power in" (less incredibly small losses - but these cannot be large or the motor would rapidly get blindingly hot and it doesn't!))

The propellor therefore speeds up until this power equation balances (actual revs are irrelevant)... when the boat will be being given a driving power exactly as it was for conventional drive. So, on this basis, if the propellor drove the boat "sensibly" before conversion, it still will in exactly the same way!

I think propellor considerations people make are really based in terms of maximally efficient connection between the prop and the water when the conversion is such one needs maximum range for a given drive battery charge. But this isn't a prime requirement in this case since one can choose to recharge at any time.

Clearly, any increase in coupling efficiency between prop and water would mean less re-charging time - but from my researches gains only seemed to be of the order of 5% at best... really quite trivial compared to the variations one would meet for meeting different river currents, etc. - not really of practical significance.

Incidentally, with our control set to maximum, the motor draws 14kW (rather than the designed 12kW) so it would seem that if anything we are "over-propped" by retaining the original propellor and its size should be reduced for the motor to run as specified!

All-in-all, our system seems to work entirely satisfactorily retaining the original prop!

Electric boat conversion - drive electronics

2008-08-31T14:23:00.001-07:00

This photo shows the electronic control unit for the drive motor - as supplied by Rupert Latham. It's a "standard" unit made by Electrofit Zapi, cost (ex VAT, 2006, £1,300, 72V 500A unit.) As shown elsewhere it is mounted in our engine space on the rear cabin bulkhead entirely under our gas box, and so entirely protected from the elements.

Note engineer Alan's neat wiring of the heavy duty (400A) connecting cables - but the runs are never more than 1m long with the drive motor only just out of sight below this photo and the batteries nearly as near on either side!

The four-barred copper device in the middle of the photo is the 300A shunt used to detect drive current. The wandering cable running across the top is a typical example of my untidy wiring - it's a multicore connecting my detector of the direction of current flow through the batteries to the control panel. The "pipe" on the right is where all connections go through the bulkhead to just inside the cabin to connect to the control panel and the other devices just inside the cabin (see other postings.) Note that ALL high currents (drive and recharging) flow in cables within the engine space with very short lead lengths.

The unit is in fact a highly complex electronic device where the details don't matter in terms of operation, but I think one should be aware the motor is fed high frequency, high current, pulses (at a rate of about 16kHZ - 16 thousands times per sec) to the armature coils and about 1kHZ to the field coils. The combination (in detail) produces speed and direction control. In many ways the speed control is much like a cordless drill ... and in the same way the combination of this unit and the motor can produce "singing" tones - especially at low speeds... although less pronounced that drills I have used!!

I have looked at the actual pulses being sent on my oscilloscope (via suitable reduction devices!)... and it is truly startling how huge currents are zinging around with "ringing" effects because of the high inductance properties of the motor windings - it is quite essential the motor is powered from the generator via the batteries which effectively "smooth" everything (like a giant electrolytic capacitor) or... electronics would be going "pop" in all directions! I haven't tried, but I very much doubt any voltage conversion devices could cope with such high-power complex signals were it not that that the generator, batteries and motor all work at the same nominal voltage (72V.)

A word on this "nominal" value at this point - I know it confuses people! The actual (average) voltage of the system in fact varies quite widely - with the generator on and the batteries near full charge, the VCS limits the generator output so that actual voltage is about 87.5V (and the batteries are charging.) If the batteries are fully charged and not in use, voltage available is about 80V. Once you start using them this drops to about 72V.... if the generator is off and you are running along and the voltage is about 60V, it's time to seriously think about recharging (although you'd have at least another hour in normal use before things became desperate!)... my point is, this "nominal voltage" is in fact just that - it varies according to what's happening!

As you can see from the picture, this unit is cased in heavy Aluminium designed to assist cooling - what you can't see is a very heavy Aluminium heat sink attached at the back - only its front plate. In our case the whole is bolted to the (steel) cabin bulkhead, itself not that far from the (steel) bottom of the boat, so cooling is quite effective.

In normal use, the unit has proved to behave nearly impeccably - but see below! It is incredibly complex and self-testing - when you turn on it runs through a self-test and only connects the high power feed via a heavy duty contactor (just visible in the photo as a black blob down left.)

Herein lies one operating snag - if the control lever is not set at zero at turn-on, the test will not complete... which can be quite alarming in that you turn on the key and there is no re-assuring "clunk" (about a second later) that the contactor has gone over and all is well... it is easy enough for the lever to have been knocked off zero fitting ropes, etc.!!

Another oddity is that after use "driving" the boat, the unit gives some bleeps (control to zero)... which then shut down... there's a lot going on in there!!

Incidentally, having seen the handbook which was clearly written for those know how it works exactly (not me!), it appears to have protective devices against almost any possibility, so, for example, I would gather (although I've not tested this and have no intention of trying) that if the propellor was suddenly stopped by an obstruction the resulting surge in current demand would cut power so fast no mechanical or electrical damage should result (other than the original "clunk"!)

Interestingly, we have observed another protection device cut in - unexpected at the time. Boating against the stream on the Thames under "Yellow" stream conditions I deliberately tested how well we could manage maintaining shore speed despite a blatantly strong river current.

To do this I was drawing 110A for more than 2 hours almost continuously, with the generator happily providing 70A and the batteries 40A. I expected to make up the battery deficit over lunch easily (as we did.) The boat didn't vibrate at all although the water noise of the propellor fighting the current was loud... but suddenly power cut by about 50%. For about a second, then came back on... and this repeated....

When I cut driving current (a bit) the boat ran longer at that full power before about two seconds of reduced power...

To cut the long story of my deductions short... then verified (I think!) by looking at this unit's handbook... this unit had overheated. Even more validated at the time by the observation it was seriously hot!

It would seem the unit has an overheat protection that is wonderful - unlike the generator, it didn't cut out entirely, merely reduced output by about 50% to allow itself to cool. And cut back in until it got too hot again.....

Given our 1 hour lunch break (that time) after which the batteries were back to full charge (generator running) I then drove on limiting my drive current to 90A - and this "cut out" effect vanished...

Obviously, this is not an ultimately validated test, but I think it was pretty clear that if you ran continously with a current in excess of 100A for enough time, this unit overheats... but not catastrophically because of its built-in safeguards.

Alan has suggested we might either (a) fit a fan to assist its heat sink or (b) even think of water-cooling its heatsink. Actually, it was quite unnecessary to run the drive that fast and I only did so to see how the system coped!....

And I got my answer. This unit overheats as we had fitted if you run drawing in excess of 100 Amps continuously for more than two hours. Interesting to find this limit. Way beyond what we actually need normally. And if you DO get the thing too hot, it self-protects without leaving you stranded... quite enough power left to "manage"... and re-sets to full power the moment it's cooled off enough! Brilliant.

Electric boat conversion - control lever

2008-08-31T13:20:00.000-07:00

The photo shows how engineer Alan neatly fitted the "joystick" speed/direction control lever in the same position as the previous standard "Morse" control. More about this below.

Below is the heavy duty on/off power switch (in "off" position - the "on" position puts the lever at "3 o'clock"- - a good chunky, positive switch!) that breaks connection between the batteries and the drive-motor control electronics (and all other 72V meters, etc.) This switch is required by the BSS, for giving total manual disconnection of the drive whilst being in easy reach of the helmsman - but is, obviously, also suitably convenient for emergency switch-off (and initial turn on! - and never mind the regulations!)

On the right of the mounting box for these two, you can just see the grey plastic of the automatic siphon break valve that is necessary to stop the generator cooling "live water" system potentially syphoning water out of the engine "backwards" through the (underwater, water) intake... in theory this would only happen with the generator "off" and so the water pump ("impeller") not operating... but in fact flows are obviously far more complex... and one can (just, if you listen very carefully) hear the valve "popping" (i.e., operating) when the generator is on... so it's clearly an essential part of the system!!

To return to the joystick control. This is (unfortunately) "linear", and so very sensitive for adjusting cruising speeds - and takes some learning! The thing is, one actually wants fine control over a small low-drive-current range (0 - 40A) whilst for larger "control" pulses of power... variations of 10's of Amps... don't really matter ... so it's a pity the control isn't logarithmic (like a radio volume control.).... Also, intitially, the control tended to "spring back" slightly to zero... but in time the unit "bedded in" and this effect vanished (and we learnt better how to operate it) - and control is not a problem now. On the other hand, it's quite impossible (we find) to operate it with one's hand (and arm) "in mid air" - the trick is to rest the LH side of one's (left) hand on the guard rail and then operate the lever with thumb and index finger.

Incidentally, I would deduce that, at least in principle, the drive electronics unit could be programmed (it's controlled by programmable chip, the handbook says!) to give a different response... perhaps more like the "logarithmic" I've suggested - but how one would actually go about getting that programming done and whether one could get the desired effect is unclear!

Initially, we certainly had some "exciting" moments operating the lever far too drastically - shooting from quiet cruising to violent acceleration!... and the boat's acceleration with the lever "high" is quite stunning - the boat (all 10 tons of it) almost jolts. Until we learnt better control, the other snag is that drive electronics and motor response is very rapid... BUT after about a 0.5s (seconds) "pause" as the system "winds up". So, "suddenly" wanting a burst of power for control it was all too easy to move the lever too far apparently getting no response... only for the propellor to effectively explode into action a moment later... far more than one wanted and requiring hasty re-adjustment, with the boat now galvanised into action... not necessarily in quite the right direction (and needing stopping!)

BUT, to re-iterate, with experience (and the lever itself "bedding in" from awkward initial "springiness") we now get extremely good boat control. Indeed, we find, better than was ever possible with a traditional drive once one is familiar with the lever and the response - although one can gain for using slightly different techniques.

In particular, if you allow for the response "pause" between moving the lever and thrust, one can get extremely positive control by deliberately applying a really short burst of power (tiller in appropriate position) - literally moving the lever up and then back down almost before the motor has responded to give the boat a short shove in the right direction - and control by little pulses of power like this can be incredibly effective... one can have the boat swinging "just so" and then use no power at all as it swings onto the required line. It takes some learning, but can be very effective... and use hardly any average power!!

We do have a snag we believe is due to the crude nature of our old hull design - if one applies high reverse power, the boat tends to "pull left" (i.e., to port) ... I'm not necessarily convinced by explanations, but live with the fact it does! The trick here is (a) allow for this effect and (b) to only use a very brief pulse of reverse to cause drastic slowing, then gentle reverse (where the "pulling left" effect is negligible) to maintain the effect.

In terms of sturdiness and weather resistance, these controls have proved entirely durable (they have never been covered for the last 14 months!.) Another plus for the conversion.

Electric boat conversion - control panel

2008-08-20T15:31:00.000-07:00

Our control panel...

Meters at the top are (left to right):

1. Drive current. Note this can run 0 - 200A in practice. The drive is so quiet one actually needs to read this to select a suitable value for cruising! Ideally this would have a loagrithmic display since one wants to choose low values fairly exactly whereas high values are only used for manouevres... hey ho, ideal world... it's OK with a bit of experience.

2. Drive battery plate voltage - analogue meter. Doesn't show enough detail to be much use BUT does act as a check... and just to show things are basically OK!

3. Charging current (from the generator.) Normally shows increasing curent as the generator speeds up from start to steady 70A. Should stay there whatever you are doing (generator on) unless you are either going very slowly or stationary and the batteries are coming back to full re-charge, at which point it drops (in jerks) as the VCS slows the generator(!)

4. Start battery voltage/charge state. Helps you decide when to recharge this (switch below)

5. Ditto for domestic battery.

Little switch below charge current meter - little switch I fitted to check readings on the drive current meter - means the charge current meter reads drive current (although the scale is wrong!)... comparisions revealed the drive curent meter had been reading 10% too high... in practice, turned out not to be important....

6. Switch below drive current meter is for the bilge pump.

7. Switch below the voltage meter is for the headlight.

8. Button below the charge current meter is for the horn.

9. Little blob below the charge meter on the right is a dual colour LED indicator which is incredibly useful - and I fitted. Shows green if charge is flowing onto the batteries, red if flowing off, (and is off for no flow.) Its simplicity hides the existence of a neat detector which is a mini permanent magnet suspended on sewing elastic inside a tiny cardboard box taped to one of the battery connecting wires... if the current flows one way, the magnet twists one way, reverse, reverse effect. The direction of twist (limited to a few mm by the box) is detected optically... switching the LED (via electronics) to indicate green for charging, red for discharging.

In practice this is amazingly useful - if running upstream on the river with generator on you can set the speed to be "just" not using any battery (LED off) or "just" re-charging (LED just gone green) ... which by fluke is almost exactly the power you need to run at legal speed against a medium current!! With this LED off, n.b., you can run forever with in effect the generator driving the boat. (It's just about visible as being green in this shot.)

10. Below the headlight switch, digital voltmeter I had to fit (a first for everything!) showing drive battery voltage more precisely... but sometimes confusing because by the way it works it can sometimes give "spoof" readings (very temporarily!) Needs an auxialliary 9V PP3 battery... I arranged to be cut off by relay when the key switch is off... and also changed to use Lithium type for even longer life... This meter can go amusingly completely AWOL in very damp weather...

11. Below this, battery charge meter, display nicked from a standard over-night-recharging meter, the rest entirely my electronics. This has a LED "bar" display, green segments for charge 60% and above, orange for 30, 40, and 50%, red below ....

My circuit uses a Hall detector to measure the magnitude of discharge or recharge current through the batteries to charge (or discharge) and electronic capacitor mimicking the state of charge on the actual batteries. I adjusted values empirically until discharge times matched theory to find recharge times weren't the same... 70% slower!. I used detector "9" above to switch the rates.....

With the meter after hours of tests seemingly OK for repetitive cycles of discharge and recharge, I (a) discovered it was only on 40% discharge when plate voltage was 60V... lowest sensible, I discovered, even if the batteries are capable of 80% discharge. I therefore changed the rates so the meter reads low and goes orange if you are at about 35% discharge..... we've never got near that since!...

My circuit uses an auxilliary battery and for first actual boating test went totally AWOL - flat auxilliary battery... changing to Lithium type, it lasts ages. I also discovered that the drive electronics (for the drive motor) completely messed up standard black op-amp chips by some internal pick-up effect and had to resort to discrete components to make the thing work! ...

Never mind what... I got it working by empirical tests and experiment. It's amazingly accurate from comparing to the digital voltmeter readings where over time I could use these to estimate battery-charge left... the check being that over a complete cycle of discharge and recharge (done many times) everything gets back to the same place(!)

The mimicking capacitor is entirely isolated with key "off" and stunningly holds charge for more than a week... but can need resetting (to "full charge" state) - red button below the bar indicator.

12. Key switch - on the left - obvious... although at the moment wrongly wired you can actually run the generator with this "off"! Woops!

13. Panel on the right, controls and indicators for the generator. Nearly all of no use in this application apart from "On", "Heat", "Start" and "Stop". Oil pressure, OK, as for any car. Temperature indicator is pain because it does NOT indicate looming problem, merely comes on for the condition and then cuts the motor... but, worst of all, after the generator has been on, for stopping it the cooling flow stops and heat dissappates inside the sound-proof caccoon... causing a fault condition needs the motor to run to cool the thing.... quite daft.

14. Small switch bottom left of generator panel (mine) overrides this fault condition - sprung switch - allows the generator to start to cool itself.

15. Not fitted at the time of this photo, another small switch to the left of 14, switched "up" causes the generator to slow to mimimum to run to cool itself to avoid the ghost overheating condition before actually hitting "stop". Can be a nuisance to use this method... and may not work if you haven't long enough for slow running before wanting to switch off! Application of 14 can be needed - which is completely fail-safe!

The panel can be covered by a perspex cover (slotted hinges at the top) - either left loose to reach under in bad weather if the boat is in use or clipped home when the boat is on the mooring.

Electric boat conversion - performance

2008-08-20T14:27:00.000-07:00

The photo shows the propeller wash for a drive current of about 60A with the boat on its mooring - quite impressive!

We have now run our conversion basically completely successfully for approx. 14 months.

Here are some results:

1. Since so many people ask, no, there is apparently no fuel saving! This surprised me since (I calculated) the system is definitely more efficient ... partly for clearly simpler mechanics but especially because one is absolutely drawing no power when stationary - at least 30% of the time when cruising (I calculated.)

However, electrical measurements show that re-charging is only about 70% efficient - not an issue I've ever heard (or read) discussed.. or even mentioned! However, it seems to be - at least for our equipment - simply a fact that re-charging is only 70% efficient.

Note that we could not hope to save on fuel usage except via increased efficiency - the power input fom the solar cells is negligible compared to the high powers involved in moving... our only prime energy source remains the diesel for the generator... so, no fuel saving (but just about the same as previously - which fits with the crucial physics that you can't get energy from nowhere!)

2. The thrust available is quite stunning - and way beyond what a conventional diesel can provide because the acceleration is so much greater. This makes boat control a world easier - although it takes some re-learning - since one can use brief bursts of intense power to set steering line (or stop or start) and then adjust quietly. N.b, I am referring to acceleration - continuous (illegal) high speed available is only slightly more than traditional drive... and one would have to consider battery consumption more carefully if you ran at those speeds for too long!

3. There is basically NO vibration at all from the drive, even at high power - a quite astonishing effect. (The surface of a cup of coffee placed on the lid of the gas box is completely still at all powers, and even with the generator on!) It is totally reliable whether powered by battery alone or the combination of generator + battery.

4. Although the generator is audible on the boat, the effect is so slight visitors who aren't informed whether it is on or not don't actually realise whether it's on or off unless asked to take notice! Even my wife once asked if it was on or not!

5. The drive batteries have discharged (about 50% max in our useage) and recharged over the 14 months without the slightest indication of any deterioration in performance. This has included long periods inactive on the mooring and other times of intense boating on the river Thames on code yellow when high powers were required at times - and even extended periods of high current running.

6. With "sensible" re-charging we have never been close to loss of battery power. In practice one has huge flexibility of choosing when to run the generator to re-charge.

On the canal, a "good practice" turns out to be to run the pounds electric and turn the generator on whilst locking - and this leaves one basically fully recharged from lock to lock! There is a slight deficit overall using this method, but it is easily made up by running the generator whilst having lunch or equivalent (only about 40 mins MAX needed, less would keep one OK) at the end of the day.....

But, one morning I boated pure electric (canal) all morning as a test. There was absolutely no lack of power available, although the battery plate voltage at cruising speed fell (rather alarmingly!) as low as 60V. However, I then ran the generator whilst we had lunch and went for a walk (as volition, not to leave time to charge!) We happened to meet some people and so total recharging time was 50 minutes. The batteries were now fully recharged - so definitely I could run the next bit, in fact on and against that river Cherwell section of the canal in near spate, "pure electric" with absolute power.

On the river, a continuous run upstream against strong current does require that the generator is on much of the time... which leaves one using hardly any battery! - but there is a vast range of choice about how much of the time. One can chose to run sections "pure electric" without fears of suddenly being out of power!

Downstream, power consumption (and need for generator) is roughly like the canal.

7. I spent ages making an unconventional-method meter to indicate "useful charge left" on the drive batteries. This works very well and supports all the remarks above. However, please note that an equivalent commercial version is now available!!

8. In practice one can tell the state of the drive batteries from the voltage across them (as indicated by our digital voltmeter) under different conditions - where all one wants is a rough idea!

For a few examples:

On the canal, normal cruising, 30-40A drive current, "pure electric", 72 volts means you are pretty-much fully charged. 70V means you've used a bit, easily replaced next lock. 68V means you might need to make up a bit more later. 64V means you've definitely got to do a bit of a recharge at lunch-time(!) (or equivalent at the end of the day.)

Generator on, 72/74V means you're probably not recharging much, but can run effectively forever. 78V-ish means you have masses of battery left if you felt like a patch of silent running...

In practice, with experience, we find you don't really have to think about detail as one comes to learn the kind of number to expect under different conditions!

9. Turn off the generator instantly (easily done - just hit the stop button!) if you see debris in the water or (on the canal) are about to pass where the side is shallow and the exhaust intake might hit or be near bottom (not needed if you cruise the pounds electric!) Check the intake filter every half day - even if only to decide it doesn't need a clean. Given these precautions, no cooling intake problems (and little in the filter!)

10. Hit the switch to run the generator slowly about 5 minutes (allowing it to cool) before actually turning off after a longer burst of running it... if it's convenient. If not, too bad, there's always the over-ride switch if it "claims" to be too hot next time you want to start it.

11. If the generator does indicate "ghost hot", hit the override switch... has to be held down about 15s before the new intake of water cools the thing enough to make the protective cut out shut up(!).

12. No reason to panic if you run aground, the drive has enough thrust to get you off (in reverse!) (seemingly) anything... with no vibration or any fear anything is being over-strained.

13. On the canal, use about 50A to get up to speed but then 30A is enough - if the boat seems slow, probably picked up weed, burst of fast reverse will shake it off.

14. High power reverse makes the boat "pull left" - probably a "paddle" effect since our hull design is far from ideal for reverse water flow!!.... Trick is to give a short burst and then low power to maintain the effect without unwanted spin (of the boat.)

N.B. that overall we find the effect of the drive completely reliable, more useful control power available than conventional drive, always, stunningly, NO vibration, drive noise level for normal running almost zero (except the water!) Absolutely NO disadvantages compared to conventional drive ... given sensible application of the generator, no limit to range, e.g..... and huge advantage of lack of noise (and vibration) in terms of pleasure and ability to talk to one another without aids... and also in certainty of reliability, even in tough current conditions.

Electric boat conversion - unit layout

2008-08-20T14:14:00.001-07:00

The diagram shows a side-elevation of how the units are arranged in our (cruiser stern) engine space.

Note how:

1. The drive motor - needing basically no maintenance - is under the gas box, thereby protected from weather ... although it also has a "roof" over it lower down. Not shown is that it is in a metal box welded into the engine space floor so the bilge is kept away from it (to a depth of about 6".)

2. The drive from the motor runs via a shaft under the generator, allowing this to be mounted centrally with maximum acces for servicing, etc. - and room to remove its sound-proofing caccoon to get at it!

3. The batteries (red) are mounted either side of the motor, meaning shortest-possible high current cable runs (and even ballasting.)

4. The control electronics is on the bulkhead completely under the gas box, shielding it from weather and allowing the metal bulkhead to help keep its heatsink cool.

5. Other electronics and the back of the control panel are in fact "just" inside the cabin (but minimally) meaning (a) they are in fact "in the dry" but on the other hand (b) they don't take up any significant cabin space or domestic arrangements!

Electric boat conversion - drive bearing

2008-08-20T14:01:00.000-07:00

This bit certainly isn't unique to our conversion - it's a version of an "Aquadrive" bearing used to connect the drive shaft from the electric drive motor to the prop shaft.

In the photo, the drive shaft from the motor is coming up from below into the (green) bearing, with the prop shaft going off at the top.

What is crucial to our conversion is, note, how the bearing casing is bolted to a strut connected to the boat's "chassis" - so all thrusts (forward or reverse) from the propellor are transmitted to the boat via this bearing (or other linear sudden thrusts)... leaving the drive motor to only have to provide the rotational torque for the propellor. There are NO propellor-created nasty forces on the motor bearings so expected and experienced wear on those is trivial.

In practice, even at high power, the electric drive creates absolutely NO vibration (although there's a lot of water noise - especially water cavitation noises under the stern which sound quite like an angle grinder at top speeds!) At normal cruising speeds the drive is almost totally noiseless except for a slight electronic whine from the speed-control electronics.

The lack of vibration is quite startling - if one observes the top of a cup of coffee placed on the gas box above the deck, the surface of the coffee is totally still. And this is also true if the generator is running. Quite a result!

Electric boat conversion - the VCS

2008-08-20T12:59:00.000-07:00

This picture shows:

On the left, a 72:12 (volt) DC:DC 400W converter which allows the "start" and "domestic" batteries (both 12V) to be recharged from the 72V drive batteries - powered or not by the 72V generator. In our case - at least for now - this recharging is done by manual choice via switches on the control panel, where one can asses the need from battery level meters on that panel (one for each of the 12V batteries.)

(In fact our wiring - by error - has a snag.. the manual switches do not actually connect the (12V) re-charging current, but cause relays to do this... powered by the (12V) "start" battery. So if the latter is flat the relay doesn't click over to recharge the battery!! In our case the start battery has nearly been that flat... but luckily not so flat a flick of a fingernail on the relay casing didn't cause it to operate! Clearly, though, the relays should be powered by the charging source - the output of the convertor... and I must change this!!)

On the right is the "VCS" - "Voltage Control System". This box of electronics regulates the speed of the generator so that its voltage ouptut (the charging voltage for the drive batteries) never exceeds 90V (>15V per drive unit) as its main function - although it has the secondary function that it always sets the generator speed to minimum after switch-off so that the generator starts with near zero load and then speeds up appropriately. Equally, via a switch I fitted, it can slow the generator before it is switched off so that the load reduces to near zero, which allows the generator to cool for about 5 minutes... which (usually) means the generator doesn't register "ghost" overheated condition when you next try to start (see under generator problems!)

The VCS unit comes with the Fischer-Panda unit - but in our case it was either faulty or Alan (our engineer) blew something or mis-wired it (or I blew something trying to find out was wrong, later!)... so the electronics inside the box in the picture is actually mine - I simply re-used the box and connectors!!

To explain, the speed of the generator is controlled by an automated "accelerator"... called the "regulator". This is a simple (but neat!) system on the generator where when a small 12V motor turns the one way, via a screw thread, the regulator moves to increase fuel flow, or, turning the other way, decreases....

The motor is driven by short pulses of about 0.1 sec every second, so that when the regulator meets mechanical end stops (one can set) either up or down, the motor simply tries to move the regulator further but can't - because it is only trying with brief pulses it doesn't overheat for having the mechanical movement thwarted!!

So, after "turn on" of the generator the VCS "issues" "Accelerate" pulses until the generator has either accelerated to full speed (as set by the mechanical stop) or until the voltage output has reached a preset value - as set via the volume-control knob visible in the photo....

From battery data, this should be in the range 85.2 - 88.2V.

So, normally, one starts the generator (batteries down from near full re-charge) and it speeds up because the VCS is emitting "speed up" pulses - indicated (in my case) on the VCS box by the dual-colour LED on the right at the top of the box (as in the photo) flashing green as each pulse is sent. This goes on flashing continuously... unless and until the drive batteries' plate voltage is in the range above (in my case, about 87.5V)... once this voltage goes above 87.5, the VCS emits a "slow down" pulse (LED flashes red) and the generator is slowed slightly.... reducing the voltage output.

With such a slight change being crucial - only about 0.4 V in 87V or 0.6% - the detecting circuit has to be very sensitive... and with changes being definite pulses of 0.1s per 1s... the system "hunts"... but very slowly and smoothed out by the generator not reacting instantly... the effect is that the generator slows in pulses (but sometimes speeds a bit in between!) as the batteries come up to full bulk recharge.... and as the charging voltage decreases, the re-charging current falls (in time, all the way to zero - although in practice 20A is low enough and the solar cells will do the rest.. only some tiny % of full recharge, less than 1%.)

When the generator is turned off at any time the VCS detects this action and then emits about 20 "slow down" pulses so the regulator is always back to min before next starting the generator.

(My switch to slow the generator before actually turning it off merely "tells" the VCS the generator has been turned off (when in fact it hasn't been) so the VCS issues the 20 "slow down" pulses whilst the generator is in fact still running... if one reverses this switch before actually turning the generator off it speeds back up again!)

Without issuing an actual circuit diagram of the electronics, people may be interested that it contains (1) a slow (electronic) oscillator creates a 0.1s pulse per 1 sec all the time which (2) is switched on to drive the regulator motor via a relay if conditions are suitable, with the polarity of the output controlled via another relay, direction being "increase" for battery voltage less than 87.5v,or "decrease" for battery voltage greater than 87.5V OR for 20s (seconds) after "generator off" signal.

Detecting the voltage o/p so accurately is done by dropping the battery voltage through zener diodes to lose 80V and then the remainder (about 7V) is compared with 7V set by another zener in the otherwise 12V circuitry....

Anyway, point is, you MUST have something to accelerate up-to and then limit the generator output to max about 87.5V and to set the regulator to minimum after turning off.

Electric boat conversion - the solar top-up cells

2008-08-20T12:11:00.001-07:00

Ideally, I would have loved to charge and re-charge the drive batteries via solar power.

Unfortunately, to have a re-charge current of magnitude anything near that available from the generator would, I calculate, need an area approximately five times that of our boat's cabin roof area and at the present time (August 2008) the units would cost approx. £45,000(!)

So... I opted for solar power merely to do final topping-up of the drive batteries and to maintain them during the ages the boat, sadly, is idle on its mooring.

To use anything over 5W (solar) cells would require a (n expensive) regulator since in bright sunlight the solar cells can produce 16.9V - and the batteries must not have more than 15V across each 12V unit or they will gas and deteriorate. But unless the batteries are extremely fully recharged, the solar cells are effectively "loaded" and output limited to less than 15v. Just.

Well, that was my information! However, it turned out that if the boat was on the mooring for long stretches of bright weather the battery plate voltage rose (slightly) above 15V. I considered fitting a low power regulator to avoid this problem - but such a regulator would necessarily lose about 1.2V (minimum) of potential charging voltage, which would slow re-charging at other times when the batteries aren't almost maximally re-charged....

One could switch between regulated and non-regulated modes, of course... but a much simpler solution is to simply run the drive motor for a few minutes (perhaps 10) once a week if this "over-voltage" situation is clearly about to happen... and it'll take a week before the re-charge gets that complete again!

Obviously, this sytem wouldn't do for anybody living remote from their mooring... but in our case I always can and do visit the boat at least once a week to check mooring ropes, etc., so if a quick check of battery plate voltage reveals it's getting close to 90V (thanks to the solar input) I simply run the drive motor a bit... which I usually want to do anyway to check all is "ready to go"!

Electric boat conversion - power principles and figures

2007-12-15T15:30:00.000-08:00

This posting could really do with a block diagram - perhaps I'll add one later!

Given questions I've been asked, I thought I should add this posting about the main theory of how the boat is powered.

The propellor is driven directly by the electric drive motor with no clutches or gears or pulleys. Details of the mechanics of this are in a separate posting.

The electric motor is (hard-wired) powered from the electronic control unit which itself is hard-wiried to the drive batteries via a high current "off" switch (in reach of the steering position) that isolates the motor control electronics entirely from the drive battery input - both to meet BSS requirements and to isolate the drive batteries entirely from any current drain when away from the boat.

The generator output (coming via its necessary internal diodes since its output is DC) is hard wired to the drive batteries. The solar cell output is (via a diode preventing reverse current flow) hard wired to the batteries.

If the generator is not running, the drive motor simply draws current from the drive batteries.

If the generator is running, this accelerates (controlled by the VCS="Voltage Control System") after starting until it provides a steady 70A (Amps) unless the batteries are coming near to full re-charge and so the charging voltage across the drive batteries starts to rise above a (pre-set on the VCS) maximum value (approx 87.5V) in which case the VCS slows the generator maintaining this voltage but reducing the re-charging current. This effect only comes in to play when the batteries are within about 2% of full recharge, so for virtually all normal "running along" conditions the generator basically supplies 70A when on.

If the boat is stationary, the batteries recharge at 70A.

If the boat is going along at normal canal cruising speed (as an example) the motor draws 40A effectively provided by the generator whilst the remaining 30A recharges the batteries. As a general statement, if the drive current is less than 70A, the generator drives the boat (but crucially via the "smoothing" effect of the batteries since the actual currents are not steady things!) and the ramaining current goes to re-charging the batteries.

If the boat is being driven using more than 70A, the generator provides 70A and the batteries the extra needed. For example, if one is using 90A, the generator provides 70A and the batteries 20A.

Note that no special switching devices are needed for this to happen - it's a basic physics rule (Kirchoff's first law.) Nor do things have to be "steady" - current flow will adapt instantly - and, indeed, in fact the output from the generator is not a "steady" 70A but "wavy" whilst the drive current drawn is not the least steady - because of the electronic speed control the actual flow is high speed short pulses at (approx) 18kHz (18 thousand pulses per second) - but overall the average figures remain pretty much OK. Luckily, as a boat operator, one needn't worry about the detail!

There is a slight pragmatic effect. Recharging whilst also running along is slightly less efficient (compared to recharging whilst stationary - but not drastically.) In everyday terms one needs a short time of stationary recharging at lunch time or the end of the day to be sure to be fully recharged. In practice, one would in any case be needing to recharge the last bit of "pure electric" usage of the batteries, and in practice the loss of efficiency for recharging whilst running along can mean you need 30 minutes of "generator on" rather than 15.

This loss of efficiency is only fractional and at no time possibly puts one at risk of reduced power available, let alone anything drastic like a "flat battery" - one merely needs to run the generator a little bit longer (we are only talking 10 minutes or so - at lunch time or end of the day) until the charging current falls to 20A (as controlled by the VCS) to indicate one is definitely back to effectively near full recharge.

This system relies upon its simplicity to work without problem. Generator, batteries and motor must all work at the same nominal voltage and so be able to be hard wired - electronic voltage conversion units would not be able to average and suppress the effects of the actual currents being in fact highly complex. They would also have to be terribly high power - for example, at least 6kW if the generator had a different working voltage.

The system also relies on the fact the batteries can withstand vast currents in either direction - actual currents flowing zing around very violently at high speed where because the electric motor is a heavy duty inductive load there are short-lived secondary effects of reverse currents through the batteries pretty much nearly as great as the current drawn.. in our case, maximum out is 200A, but the flow "rings" so there are also very high frequency reverse spikes of very nearly the same - very, very brief, but if the batteries could not cope with this kind of effect, would be disaster.

Overall, because the system is Generator -> Battery -> Motor control ->Motor with nothing complicated in between, all possible disastrous so-called secondary effects are eliminated. Where all these potential secondary effects are to do with suddenly disconnecting a heavy inductive load which can produce incredibly high voltages ... can blow electronics and punch through insulation. The simplicity of our system is utterly essential!

Electric boat conversion - the generator

2007-11-09T10:39:00.001-08:00

The photos show (1) the generator top view - it's very densely packed with equipment!... and (2) with the sound-proofing cocoon fitted.

In my researches, it became almost immediately apparent that only Fischer-Panda supplied suitable generators for our conversion - because only they have a range including a choice of (nominal) DC outputs, including the (nominal) 72V of our drive motor (and therefore, drive battery pack.) To have had a system that needed to convert voltages would have been very complex with a need for extremely high-current voltage conversion - basically, not practical with a motor drawing up to 200A... and a recharging current of up to 70A.

From my calculations - and other advice - it seemed unlikely our average power consumption could possibly be more than 4kW... so I opted for a 6kW unit to have reserve.... just as well, because in fact the unit produces 4.9kW maximum - and a recharging current of 70A at that maximum.

I found out about F-P generators first by directly by emailing F-P... and, delightfully, one of their directors, Barry Fower, replied, quite rapidly, in person - and appeared to be intrigued by my plans and basically thought they should work OK, which was very encouraging.

When I later contacted Rupert Latham about an SEM motor (and its controls,) it turned out he could supply an F-P unit.... and even better, by the time we actually decided to go ahead with the conversion, by pure chance happened to have a slightly-used unit for sale - terrific saving in cost.

The units are, frankly, far more sophisticated than we really needed... but tried and tested, so worth the cost. They also come with a sound-proofing cacoon and "live" water-cooled exhaust, which makes the latter basically inaudible... although you can (and crucially) hear the water "sploshing" in the exhaust separator - and you can (of course) hear the generator running - and, indeed, it vibrates the boat perhaps slightly more than we'd hoped, although the effect is very minor. With hindsight perhaps we should have mounted the whole unit on its own rubber mounts (as well as the motor itself having internal mounts) ... although vertical spacing was pretty exact... the cacoon only just clears the sound-proofing under the deck boards above!

I hadn't actually initially intended that the generator should run at maximum output all the time, necessarily... but every extra amp re-charging means extra time free to run blissful "pure electric" ... and the unit seems quite happy - not labouring or straining - chuntering away giving a steady 70A.

The unit requires quite a bit of auxilliary equipment - most of which came with the unit - but fitting took quite some thought and "tweaking"....

The handbook that came with the unit didn't altogether help - it was really for a slightly different unit and was often hilariously... but also, misleadingly, at times.... translated from the original German....

I'd checked that the dimensions meant the (cocooned) unit could slot into our engine space through the existing deck supports without modification - and that the weight (in the mix) would mean overall ballasting was about OK. In discussing the conversion details with engineer Alan, he brilliantly came up with a plan meant the unit could be mounted centrally for maximum access with the propellor drive shaft below- see separate posting for plan.

Basic facts are:
The unit is a 6kW 72V with freshwater cooling, including exhaust
Size: (lbh): 520 x 470 x 580 mm or 20.5" x 18.5" x 23.5"
Weight: 130 kg (286 lb)
Engineering contact: Chris Baker of F-P, email chris.baker@fischerpanda.co.uk

The fitting involved various slight problems - or at least things to be considered - where Chris Baker was invaluable with his advice... although I have to confess I adjusted some things according to my own decisions and, indeed, experiment! I've listed various points below, no particular order:

1. The unit requires an external fuel pump (although this was supplied with the unit.) Alan had some problems wiring this to switch on correctly - I'm not sure of the detail... but I think this was because the handbook was for a slightly different unit. (We used the existing boat's fuel tank)

2. The handbook outlines the cooling water intake plans for the two cases of (a) generator above the waterline and (b) below ditto... but not for "half-below" - our case! In fact the advice was to treat it as "below". This meant that the cooling water intake had to have external pipes fitted to a siphon-break device (which we had to buy) to avoid water being siphoned "backwards" out of the unit when it was switched off and the water pump - "impeller" - had stopped. The siphon break had to be fitted well above the unit - above deck - we found a convenient spot beside the "control box" - where the drive motor speed control was fitted - in a standard Morse control position.

Fitting these pipes was not altogether straightforward on our "used"/older model - newer units have a small loop of pipe that comes out through the cocoon that you remove and fit "feeds" to a siphon break if required, but in our case Alan had to break into internal (flexible) piping and make suitable holes in the cocoon.

The siphon break device has an automatic valve - we certainly need it - you can hearing it "popping" to let in air and break siphon effects!

3. The cooling system means the raw water drawn in cools an internal water+anti-freeze cooling circuit via a heat exchanger. But this system requires a "header tank"/reservoir well above the unit. The unit came with a crude (small) plastic reservoir and narrow bore plastic piping which Alan replaced with his own piping - again requiring a hole in the cocoon - leading to a metal tank he created beside our gas-cylinder box - you can see the yellow flexible pipe in the top photo above.

If the motor overheats until the coolant boils ... and, yes, we had that happen just the once! - the effect of Alan's yellow pipe is totally startling... being such a long fine pipe the bubbles coming through create an ear-shattering loud crackling noise... this all came about thanks to an intake blockage and consequent failure of the impeller.

4. The cooling water intake comes in via a filter, external to the unit. This has to be above water level to avoid any risk one floods the boat for opening it to clear debris! Contrariwise, there is a catch to this, the lid must seal air-tight after cleaning... but you have to be very careful this seal is made or if water is NOT sucked in within a short time (even 30 seconds matters) the engine starts to overheat. I think my failure to make sure of this led to the one time we had a drastic overheat. Interestingly, the initial reason I realised the intake had gone seriously wrong was that I suddenly realised I could hear the exhaust "popping" when I went ashore to work a lock. Our exhaust didn't "pop" normally.....

This water intake is a weak point in the system. Especially on the canal, the intake can very easily become blocked... and, with hindsight, our intake should not have been mounted on the starboard side meaning it gets terribly close to the bottom and edge of the canal if passing a boat(!) My solution is very simple - never turn on the generator if the canal looks full of debris, even to simply turn it off right there and then if you can tell you are about to have close to the bank (and possibly aground) ... so, in many ways it's not a major problem, but you do need to operate sensibly to avoid potential blockage.

I'd been warned the impeller might need replacing after a blockage and so bought spares ahead. What I hadn't really taken into account was that to refit a new one would be so tricky. Where the major problem was access to unscrew the cover on the pump - two flexible cooling pipes pass right in front... one, intake water, so safe enough to remove. The other, internal coolant, so disconnection would mean anti-freeze everywhere and a whole procedure to re-charge without airlocks.....

But the worst thing was that the retaining bolts were ordinary "slot head" and without an obstruction tool almost impossible to unscrew without damaging the slots. I've since obtained hexagonal-head bolts can be unscrewed (or refitted) with a side-access, ratcheted, box spanner.

Overall, I managed the replacement and it's worked perfectly ever since, but I would recommend one replaces the retaining bolts with hexagonal head before the unit is even put in place to ease replacement of this rather fragile impeller.

I have been advised, incidentally, that the whole pump can need replacing due to the abrasive nature of canal silt... which would not be an easy task and so I wondered about an electrical substitute.... not simple, it turned out... if the electric pump ran after the motor had stopped, cooling exhaust water would be sucked back into the actual cylinders of the motor causing, of course, almost total damage!!!

Being me, I decided that the real answer was that this fragile impeller should feed water to silence the exhaust (where failure would merely mean a temporarily loud exhaust) whilst the actual engine cooling was done by something less fragile.

I had no reply from F-P when I asked how easy (or not) it might be to separate the exhaust-silencing water system from the engine-cooling system. I may yet find a way to do that... who knows?

5. The engine cooling system has yet another problem. Because the unit is mounted in a sound-proofing cocoon, this is also a thermally insulating cocoon. And because the cooling stops the moment you stop the generator, heat generated quietly spreads after switch off...

But the unit has masses of safety cut-out devices, especially for over-temperature. So I slowly discovered it would fail to re-start immediatly after a burst of recharging because it "thought" it was too hot. To be honest, in normal daylight the indicator on the control panel is so dull I hadn't noticed it... I'd merely discovered that for trying to restart several times it was suddenly OK....

Penny only dropped when I suddenly did notice the indicator.... and fairly rapidly realised the problem... cut-out wouldn't let me restart when what was needed was that the engine ran to cool itself..... trying to restart turned the indicator off because, after about four attempts, enough cooling water had come in.... obviously daft catch-22, it must be possible to "tell" the system to run itself to cool off enough to be OK....

I eventually found in the hand-book this problem had been considered and there was an override button. IN the unit, INSIDE the sound-proofing... lordy, to operate that would be so non-pragmatic, I'd have to lift the deck boards, undo the cocoon, find the...

But, in any case, it turned out our unit didn't have that button! But I did have a circuit diagram so knew which terminals it was supposed to connect across... sure enough, connect those, the start solenoid (visible in the photo above) shot across and the fuel pump came on although something in the control panel made the most awful buzz...

I asked Chris (email) about that, he said it sounded like a relay chattering and it worried him. Fair enough, it worried me. He also said the trick was to run the generator on no load for about five minutes before switching off to let it cool.... didn't say how on earth I was supposed to run it on no load when just everything had dire warnings it must not be disconnected from the batteries it should be charging....

Ah well. I know about relays "chattering" for having too high current... so I added a resistors experimentally until the relay didn't chatter but the start solenoid still clicked over. And a switch on the control panel... tiny thing. If you want to restart the generator when it's hot because it needs to run to cool itself... hold the sprung switch .....

6. The unit comes with an external electronic "VCS" (voltage control system) unit. In the case of our second-hand unit this either arrived faulty or Alan mis-wired it and blew it or Alan mis-wired it (it certainly wasn't doing the right job) and I blew something trying to work out what was going on. But the importance of this unit and what it does is something needs a separate posting. For this posting, about the generator, I'll simply say that that I was advised that a common way to avoid the "ghost" over-heating problem was to run the generator "off load" for about 5 minutes before actually switching it off.

This may sound a simple instruction, but this advice completely contradicted other advice that the generator must never be disconnected from the batteries it was charging (if running) without risk of damaging its coils and output diodes. To go "off load" what one needed to do was SLOW the generator until it was not providing any current, you must not literally disconnect it. I could adapt my VCS to do this by (yet another!) added little switch. So you hit this switch, the generator slows, run like that for about five minutes, the unit is cooled enough not to register overheated condition when you next want to start.

Sounds simple, but there can be reasons you must stop the generator almost immediately - for example suddenly spotting debris in the water would almost certainly block the cooling intake. Or, it's time to enter a river lock, generator can't be on. Or you just don't want the generator on that moment!....

This doesn't actually matter, you can use the over-ride switch described in (5) above. But to cool by slowing the motor is less likely to build up strains so if one has time it's better to use this method - you can survive by over-riding, but you are at risk of running things too hot - and also the risk that the overheating was for a different reason (such as the impeller failing) so using the over-ride switch must be done quite carefully and watching to see that the over-heat indicator goes off after about 20 seconds... much longer and there may be a problem needs different consideration. Therefore, cooling by slowing is safer and better. And the over-ride switch must be sprung so there is absolutely no risk you over-ride the temperature safety device when it may be indicating a catastrophic fault without you realising. By having a sprung switch, you are consciously over-riding for this one specific condition that upon re-start it can take about 20 seconds for the unit to pump enough water to cool the unit to working temperature.

Further details - especially the VCS - in other postings.

Electric boat conversion - the batteries

2007-09-15T14:45:00.001-07:00

Key to the success of our conversion are the special Odyssey batteries. Bear with me, it gets complicated.... (the photo shows 3 of the six we use - the untidy brown wire is to do with metering available battery capacity... complex and unusual... see separate posting.)

All conversions I'd heard of tended to assume one charged ones batteries for a day's cruising and then recharged them overnight - except hybrid systems where, when running along driven "conventionally" by the diesel, it re-charged drive batteries for use when you decided to run "electric."

But the hybrid systems didn't suit my idea - highly complex with clutches and extra alternators... and you needed a perfectly good conventional diesel... we couldn't use our old engine, it was clearly on the edge of falling apart!!!!

No, I wanted a really simple system with the propellor permanently connected to the (electric) drive motor, no belts or clutches.... but how big a battery store would one need?

From other conversion attempts I'd researched and advice and my own (very approximate) theoretical calculations, about 800 A-hr to be sure not to run out of power... although in our case we could probably "get away with" as little as 400 A-hr....

But... where on earth would they go, safely? Without virtually rebuilding the boat, how could one ballast sensibly? ... All advice seemed to be that standard traction lead acid cells worked best... 2V 100 A-hr units, so for 72V and 800 A-hr, this meant 8 x 36 cells.. 288 of them!!! All needing to be slightly spaced for safety reasons. One advisor suggested putting them under the bed.... and then added that they would need a containing lid to careful vent any (hydrogen) gassing out of the cabin to avoid explosion....

I found it difficult to hear this keeping a straight face - the idea of having a potentially exploding bed did not appeal, sheer numbers of cells and their mounting sounded horrific, cable lengths carrying currents to the motor would be quite long for currents approaching 200A....

And then, even worse, they couldn't be recharged (I was told) at more than 20A...

So if we had 8 "columns" (to make up the 800 A-hr) it would need 160A running for 4 hours to recharge the pack from 80% discharge.....

4 hours sitting recharging didn't sound much fun on a quiet countryside mooring. And, besides, the generators I'd researched could only do, say, 80A, and that, pushing it. So, 8 hours recharging, absolutely not on!!

So I puzzled and puzzled trying to think of a solution......

And then I suddenly realised... well, my initial figures suggested we might use about 20A for normal running along ... which I doubled in case of losses I hadn't thought of. (Not a bad estimate... it turns we use 40A for normal running along!) I suddenly realised that if we could recharge at (roughly) 80A including whilst running along then it was a whole new ball game... if I could find batteries that could recharge at the full generator maximum rate then it would become a question of "how much of the time must the generator be running", rather than "how far can one run on a charge"... and, indeed, the battery pack capacity merely had to be enough to make decent chunks of time free to run "pure electric" compared to times running "diesel electric", with the generator powering the motor and recharging the batteries.

I was blissfully unaware that the generator manufacturors and boatyard engineer Alan would nearly have a heart attack at the idea of running the generator whilst taking (potentially highly variable, including more than the generator could provide) current to drive the boat and only found out they thought this might be a problem after I'd perfectly successfully done this...

But that's to look ahead. My theoretical cogitations had got as far as "if I can find a battery-type can recharge at up to, say, 80A, we only need 100A-hr (say)"... where I'd worked out we should probably then have to run the generator about a third of the time... an extraordinarily accurate prediction, it turned out - for canal useage, at least... although it also turned out one needs a bit of extra recharging for true full recharge.

Here I hit an impasse. I knew the idea of such batteries couldn't be silly - hybrid cars exist. But I could never get near any idea of a simple supply and the type used (as far as I could divine from internet search) required terribly complex re-charging circuits.....

I slightly despaired. But then some family friends from "up north" phoned for my birthday (January 2005) to sing "Happy Birthday" down the phone... well, they call it singing. Very sweet of them (and also funny!) Issy asked, as one does "How are you doing?!... I said "Fine except I can't find anybody makes the kind of battery I want...." Issy relayed this to her husband Ali (Alan.) I'm not sure how many beers Ali had had, but I heard him say "Edwin's wittering on about batteries?... I'll find him a supplier..."

In fact all he did was to open their local Yellow Pages and pick out a name (and the phone number) basically at random... I was fully aware of this... but, with no other avenue to pursue, I tried phoning to thereby contact Brian Shaw of DC technologies, in Halifax....

I sketched my conversion plans briefly, verbally... but then suggested I email the whole plan to see if he came up with a battery solution... he kindly studied that, came back with an email saying best bet was... standard traction cells... so I emailed back and said the quivalent of "No, no, I need something quite different... but thanks for the interest..."

Next day.. I'll never forget, another email from Brian. Said he'd "Put his thinking cap on"... what I needed was Odyssey batteries... calmly said they could withstand recharging currents in excess of 200A for a 100 A-hr unit...... and in the flurry of emails that followed, it turned out he could not only supply the things, he'd worked on their development in the USA some 20 years before... so he could tell me ALL about them... what was to become crucial advice about optimising recharge rate and all the rest.

Nevertheless, the key facts came across very fast... and complete solution for us. No gassing when recharging. With that rate of recharge OK, we only needed 100 A-hr - so, 6 x 12V units... and they could even go in the engine space... so no alterations of domestic things, no batteries under the bed, short high-current leads... I raced to do an approximate ballasting calculation...

Oh my goodness, if we removed the existing engine space ballasting, ballasting should be almost exactly as it had been.....

Yet another very approximate calculation that turned out amazingly accurate. And, yes, simply very lucky. My pre-calculations merely showed that there shouldn't be at least a major problem, didn't avoid one that the same calculations might have revealed!

Some technical data: the 100 A-hr units are model PC2150:
Size (lbh) 330 x 173 x 239 (mm) or 13" x 7" x 9.5"
Weight: 34kg per unit (so six weigh 204kg (450 lb.)
Our cost, very approximately £200 per unit... but totally dependent upon the lead market which is going through the roof at the moment.....
Can discharge to 80% with no problem - but can be re-charged from "dead" merely taking longer. Cycle life is around 550 for 80% discharge cycles, but more for lower % cycles. No gassing when recharging for re-charge currents up to >200A, so long as recharge voltage is <15v In fact the way the batteries behave - although completely OK and better than that - is far more complex than this simple data appears to state., but I think that should go in a separate posting about "performance" - I've now had masses of time observing what happens in practice and hope my observations may be of use to others!
Brian's email is brian@dctechnologies.co.uk

I've not met anybody not startled our system works terribly well with such a small battery pack - the idea of cyclical recharging seems to be "foreign" to people considering electric conversions even though WW2 subs (let alone other things) used or use it!.....

Perhaps people want the "ideal" of an electric boat that recharges by magic. That's almost true if you could plug in overnight... but you can't, way out in the countryside. And even not in the countryside, you'd have to be sure to arrange a plug-in point..... maybe some people like the idea of planning their boating holiday in that detail... we feel the a major point of narrowboating is to travel at whim... change one's mind if the weather changes, whatever...

The "cost" of that freedom is that you need to run the generator from time to time....

Not exactly an arduous cost with the generator so silenced (see separate posting) most people scarcely notice whether it is on or not it in the first place! And perhaps I should comment that in people's plans for conversions like ours they seem to forget how much of time "boating" is not actually travelling along......

You wait for locks. You wait in locks. You stop and have lunch. You stop for a walk. You stop at the end of the day and have to find a shop...

Which actually means, we've found, you can boat "electric" almost all the time so long as you turn on the generator "when it doesn't matter".. meaning, you are so busy doing other things or not there at all you don't even have to live with its slight hum and vibration!

Ah, as a boating friend typically teased "So you leave the boat running annoying people moored next to you..."

Um. Well, most people we've asked don't notice whether the generator is on or off at 2 metres away. I always know... but, then, I know whether it is on or off! At 4 metres, I would be being terribly particular to say I can hear it is on....

But the answer to the tease was fact. "Well, if they did notice it was on, and most people don't, it only has to run 40 minutes normally on a mooring at lunch or end of day to be right back to full recharge."

Now that's the beauty of these rapid-recharge batteries. In practice you never go near 80% discharge, just use about 20% and then there's always moments to recharge that... not quite fully, but pretty close. 40 minutes at lunch or end of the day is enough to make up slight losses and do the complicated final stages to be fully "bulk" recharged. 40 minutes when a neighbour would be hard-put to even notice the generator was running...

Metering the batteries to have a decent "at a glance" indication of useable charge left was an electronic nightmare... I'm afraid you can't buy it. I solved the problem... but that's another posting.

Electric boat conversion - drive motor

2007-09-13T12:06:00.000-07:00

(Sorry - terrible picture - I must have shaken!)

Talking with people about my ideas of converting to electric drive, it was very curious to find that almost anybody to do with narrowboats assumed an electric motor couldn't "really" be as powerful as a direct-drive diesel. I didn't have this misapprehension for being fully aware that the biggest and fastest ships are... driven by electric motors!!

No, no, all that matters is that the motor has the same potential power as trad diesel - of itself an electric motor is simply as (potentially) powerful as you choose to fit!

Question, though, what power rating would suit our boat, to be at least as powerful as the (then) existing 1.8l BMC.

It was quite hard to know how to find a suitable figure - all the conversions I'd heard of had, by report, not really been as powerful as conventional drive - although it was hard to be sure if people meant actual immediate power was lacking or that they ran out of power for the batteries losing charge and/or that a weaker motor was fitted in order to conserve battery charge....

However, I had by now been on a trip on a neighbour's smaller, lighter, overnight re-charging fibreglass day boat - fitted with a 4kW motor, top speed more than adequate, but above all, the "punch" of acceleration quite startling.

I did some purely theoretical sums about accelerating our 10 ton (or tonne - they're much the same!) boat, allowing only 50% efficiency... and decided 5kW should be enough. So, from the range of powers I'd come across, 8kW should be definitely OK. Therefore choose 12kW to be absolutely sure!

Please be clear, there is no disadvantage in having a potentially high power motor - it will only use more power if you supply it! And the extra cost for higher power is not really very significant.

I should perhaps mention here that a great many people are fooled by "nominal" power ratings for diesel engines - and this can be why some think electric drive can't be as powerful! Our 1.8l BMC was nominally rated as 42 bhp. And numerically 12kW is only 16 bhp (or so.) But this is actual power as opposed to a rating dreamt up ... I'm not quite sure how! To jump ahead, let me be clear that 12kW electric is categorically as powerful as 42 bhp nominal - and acceleration is at least ten times as great! In saying that... our 12kW motor actually draws 14kW "flat out"... but that's still only 19 bhp.

I investigated Lynch motors specifically, first, because that is the type fitted to our neighbour's boat - and very neat and small it is. They are not desperately expensive, are wonderfully simple using extremely powerful permanent magnets, and are amazingly light for their power ratings.

But, I searched around on the Web and also discovered "SEM" (Seperately Excited (field) Motors) motors - and somebody who'd been using them for conversions of wherries on the Norfolk broads. They cost about the same for the same power, although they weigh nearly twice as much! In fact they are high power servo motors where speed and direction is all (highly complex!) electronic - so there is no multi-split commutator (liable to cause more brush wear and failure for shorting in the commutator breaks) and reverse is entirely electronic, whereas the Lynch-type motor needs high current contactors for reverse - and anything electro-mechanical is more likely to fail than pure electronic.

However, in choosing between the two types, what really decided me was that

(1) the supplier I'd found, Rupert Latham of Stelco Yachttechnik, had fitted both Lynch and SEM motors, but in his experience the Lynch motors had a pronounced whine... NOT something I wanted! and

(2) Various other reports of conversions I'd heard of all seemed to recommend a Lynch motor had a reduction pulley (or gear) for best performance.... whether correctly, who knows! I came across a lot of disinformation in my researches!... whereas the SEM type could drive the propellor directly.

(3) The SEM motors work at nominal 72V (volts) whereas the Lynch devices mostly work at 48V. The currents the SEM motors take are therby lower for the same power - and we are talking whopping currents! 200A in our case - would be 300A at 48V! - so short lengths of 400A cable are OK. But for 300A.... cable losses would easily escalate (and they might get hot!)... one would quite possibly have to be starting to consider busbars

To avoid the cost and potential failure of any sort of pulley or gearing mechanism struck me as well worth the extra weight of an SEM motor.

Rupert, incidentally, said according to his data, 8kW should be more than adequate for our boat. On what basis, I'm not sure, since nothing I'd been able to track down seemed to have convincing arguments people actually knew what power a 38' narrowboat might need!

Incidentally, another reason for choosing an SEM motor is that they are the type used for fork lift trucks, crane motors, etc. - been used for yonks as sturdy high power drive units whereas Lynch motors, yes, have proved to be extremely good, but are promoted not least for their light weight. Assuming my ballasting calculations worked out, in a narrowboat a bit of weight wouldn't matter - especially if it merely replaced previous ballasting blocks!

Technical spec of this motor is:

10kW SEM motor upgraded to 12kW for the fan fitted (visible at the left-hand end.) To be honest, I'd wanted a genuine 12kW rated unit and Rupert rather rushed me into accepting this particular version - not that it doesn't work very well!

Nominal working voltage - 72V (so max current approx 200A)

Size: (length, diameter), 539, 304 mm or 21.5", 12"

Weight: 102kg (225lb.)

Approx cost (pre Vat) £1,800 + £100 for the fan.

Supplied by Rupert as above, email rupertlatham@tiscali.co.uk

I'll deal with the drive-shaft details and control unit and overall boat performance in other postings, but, be clear, this tiny motor performs quite incredibly well. It is basically totally silent - although at certain low speeds between it and the control unit there is a slight audible slight tone...

For mounting, Rupert provided "laser cut" mountings - why it should be so grand they are laser cut I don't know!.... perhaps because that way they should have no hidden metallic faults. Alan bolted these mountings to his adapted frames using standard rubber engine mounts - the motor doesn't really vibrate at all, though.

The motor is coupled to the propellor via two flexible bearings (ball races) and a shaft, where the stern-most transmits all the linear thrust from the propellor directly to the hull - so the motor is only providing torque.

Electric drive conversion - main ideas

2007-08-23T12:12:00.000-07:00

This picture shows our boat the summer (2006) before conversion - but it looks just the same now!

It's a 38' ex-hire boat, all steel, cruiser stern, Colecraft design, originally built 1982. My wife, Jane-Gordon-Cumming, and I bought it in 1997 in working but not exactly wonderful condition! Since then many things have been altered to get and keep it in good condition and and make the domestic arrangements more convenient.... to suit us, anyway!

By the time this photo was taken, we had already been wondering about conversion to electric drive and so had recently had several major things done to keep the boat up to scratch...

1. A "deep" repaint - most of the metal angle-ground back to "bare" - and the boat re-blacked. Roof and gunwales painted with "grippy" paint - i.e., sand included (this also has the advantage that the roof isn't glossy and so doesn't reflect bright sunlight too badly!) New name (yellow) patches and lettering.

2. New stern tube - i.e., prop shaft tube/bearing. New "shoes" - plates welded to the bottom and along bottom edges.

At this point the boat still had an old 1.8l BMC standard direct-drive diesel which despite all efforts was getting noisier and noisier... and in fact this photo was taken shortly after we'd just decided to seriously consider conversion to electric drive again - our otherwise lovely few days on the Thames (in the second heat wave of 2006) was nearly spoilt by the sheer noise of the engine...

Domestically, the boat has an old Paloma (gas) water heater that we find works superbly. During our ownership, central heating was fitted using an Alde (gas) boiler - again, works superbly. We don't "winterise" our boat against cold weather, simply turn the boiler on at lowest setting! Oh, and put out a box of chemical drying agent - the cabin is thereby completely free of nasty damp over winter months.

I changed the bow doors to open inward or outward - like a cat flap - the doors bolt to the frame, but the frame itself hinges the other way and bolts to the cabin. Absolutely crucial adaptation - if the doors are opened outwards, people sitting on the tiny bow deck have to lean past the doors to talk to each other and they are in the way for crossing the deck when locking, etc.. On the other hand, if they open inwards, you can't put up the dining table... and they get in the way of watching TV.

The gas cooker and gas fridge were updated during our ownership - the cooker is actually faster than our home gas cooker! - and the fridge... well...

Compared to an electric one, brilliantly silent, of course. However, tended to fail in hot weather... for 2005 I added computer-type fans (turned on optionally) to help circulate the cooling air it needs to have a chance to work. But, of course, these only circulate the cabin air.. which can be terribly hot. As it was in the first 2006 heat-wave when we boated to Banbury and made some nice cheese from the milk.....

So I thought a bit and realised there was a source of (water) cooled air in the cabin bilge. Snag, when lighting the fridge it definitely leaks a bit of gas before it lights. Wouldn't want that building up in the bilge! So I drilled holes in the side of the fridge cabinet above gas level and holes through to the cabin bilge under the dinette seat to its right and connected these with tumble-dryer hose. So for the second 2006 heat wave - the trip when this photo was taken - if you turned on the fans it drew up genuinely cool air.

The milk didn't go off and the fridge stayed cold. Fascinating to feel the air coming out from the fans when you turned them on - started desperately hot and then cooled... and cooled. And the fridge worked. There's an idea that gas fridges don't "really" work which is actually rubbish. In fact you can get electric fridges use the same principle - I had one at one time! The advantage is that they are completely silent. But they DO need (as does a compressor electric fridge - but slightly less crucially) what us scientists call a cold "sink". In our case, cold air from the cabin bilge.

Anyway, so, with our engine noisy and vibrating a lot, we started to think seriously about trying my idea of electric drive....

I'd idly thought about this frequently by the time this photo was taken and even phoned people up or emailed them to see what sort of things were available. And I'd chased other conversion attempts and read about them eagerly only to deduce they... didn't really work very well!

Yes, there was a solar boat heralded in the press but one of our friends had met it... apparently it couldn't accelerate or decelerate normally or that used too much power. I'd received encouraging data about "hybrid" boats. Encouraging until I phoned to visit one.... the BW receptionist said nobody was around to talk-to. I said, but you must have heard what people are saying about it, are they pleased? She said "Lordy, they are forever out of power and wondering how to get it working... it's never ready to run electric first thing..."

Out of the mouths of babes and sucklings and receptionists.

So I set myself a list of what I wanted and decided to see if it could be achieved:

1. The boat must be able to run exactly like a conventional narrowboat... meaning..
2. No need to arrange ahead charging points or whatever. It must be able to recharge itself so you could carry on indefinitely if one was stalled for bad weather or simply changing your mind... not to be able to decide things at whim would ruin the feeling of freedom narrowboating has!
3. The boat must have at least as much power as conventional drive.
4. We'd spent such ages adjusting domestic arrangements to make us happy, the conversion must go in the existing engine space.

Point 4 was a major stumbling block - I'd gone as far as asking an "expert" to see our boat and suggest a system. Lordy, he completely ignored all we'd discussed by email. We "MUST" have a ton of batteries under the bed. And, be clear, they might explode, so lots of safety considerations. I decided not to expostulate and listened in disbelief. Engineer Alan glanced at me bristling the man was a fool and curiously realised I was just keeping very quiet and mildy asking questions meant the man dug himself even deeper into the absurd....

My brother-in-law had come along said over lunch "the man's appalling!" I said dryly "Yes, Alan doesn't like him, either... I can see why."

Des (brother-in-law) went back to his idea we'd do better to get a new boat altogether designed for the job. I love him dearly but this was financially utterly out the question and besides the point was to find out how to convert OUR dearly-loved boat with all the little domestic alterations I'd sweated over for hours to this electric drive.

Oh, I didn't mention that I'd made under-bed drawers which.. don't work terribly well, but are sealed from whiffs from the holding tank. But that's a problem still to be answered, Jane still finds the loo smelly and off-putting. I'm trying to find a unit to answer her complaints... there seems to be a choice of two... macerator unit or vacuum unit.

Before making other posts to reveal how I resolved the drive problem - with masses of useful advice when I found it! - let's be clear all those problems were resolved. The converted boat now works exactly as my requirements demanded. Truly wonderful.