Modfications and report July 2010

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.