Balmar regulator failure.

[Porthandbuoy]

Day 3 of my summer cruise and my Balmar alternator regulator has packed up.
I’ve run all the diagnostic tests in the manual and there is 0V going to the field windings.
If I jumper 12v to the field windings I get output from the alternator, so that is okay. Trouble is, no regulation.
Long term solution is a new Balmar regulator.
Short term solution that will let me continue this cruise could be a potentiometer that would allow me to control the alternator output while watching the battery monitor.
What value of potentiometer would suit?
Any other ideas please?

NB. Currently in Glenarm marina NI. Plan is to head south before crossing to Isle of Mann.

 

[yotter]

I would be worried about high voltages upsetting the boats electronics and possibly causing damage. I have seen 16V from a defective alternator. Can Balmar not send you a replacement regulator to either Glenarm or your next port of call. You don't say if you have another way to charge the batteries at sea. I would also consider getting a complete new alternator from perhaps the starter alternator company in Plymouth (try google) they are very helpful and that way you will have a spare ( I carry a spare for my VP engine). Can't help with the potentiometer question.
Having had similar issues during summer holidays I feel for you.
Angus

 

[Porthandbuoy]

Thanks for the reply @yotter. I have 60 Watts of solar that can keep up with my instruments but not the autohelm (on the rare occasions the sun shines).
Heading for Bangor tomorrow or Tuesday and will look for an automotive remote regulator there, doesn’t have to be Balmar.

 

[rotrax]

Day 3 of my summer cruise and my Balmar alternator regulator has packed up.
I’ve run all the diagnostic tests in the manual and there is 0V going to the field windings.
If I jumper 12v to the field windings I get output from the alternator, so that is okay. Trouble is, no regulation.
Long term solution is a new Balmar regulator.
Short term solution that will let me continue this cruise could be a potentiometer that would allow me to control the alternator output while watching the battery monitor.
What value of potentiometer would suit?
Any other ideas please?

NB. Currently in Glenarm marina NI. Plan is to head south before crossing to Isle of Mann.

A selection of bulbholders and 12V bulbs with connecting wires can enable you to manually regulate field current. Feed the field connection with the 5W side of a stop/tail lamp bulb, read the alternator output. If too low, swop to the 21W side. If too high, you need something in the middle.

You are using the bulb filaments as a resistor. A simple getout. You can work it out with a bit of experimenting, with stuff from a scrapyard or a car accessory shop or garage.

This trick got a Lands End Trial competitor through the night and to the finish back in the 90's. I call it 'Electricks'.

Give the Glenarm HM best regards from Jarrow Lily. He was most helpful when we were there last trip in '22.

 

[Porthandbuoy]

Great idea! But all my lamps are LED

 

[Boater Sam]

Have you an electric heater that you could open and tap into part of the element as a variable resistor?
Hairdryer, toaster?
Torches with bulbs?
Strip the carbon rod out of an old dry battery? Not sure if alkalines have one.
Even a potato will make a resistor if you jab 2 wires into it at the right spacing. Not very stable though.
A spare engine heater plug?

 

[Porthandbuoy]

Update:

Many thanks to @rotrax for the lightbulb trick. I got hold of a vehicle lamp holder, a 21W lamp, and was able to regulate the alternator output by varying engine rpm. With the batteries down to around 80% they would take 20+ amps. As the voltage approached 14.4V and the amps dropped off I backed off the rpm to maintain 14.4V. When the amps reached single digits I kept tweaking the rpm to maintain 13.8v at the batteries. It all worked quite well.

I took the Balmar alternator + regulator and the original 80A Hitachi alternator to E.S. Alternator repairs in Kirkintilloch. Both alternators tested fine and delivered rated output. The Balmar MC regulator was dead, no field output.

Can’t figure why the previous owner bothered fitting the Balmar, at great expense, just for an extra 20A which is unlikely ever to be needed. I’ll be refitting the Hitachi alternator.