Electric boat conversion - control panel

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.