Battery over voltage

[Iain_S]

I also had an overcharging problem, which I assumed was due to the alternator controller, and described here When I was back to the boat recently, I started measuring things again, and found that while the starter battery was being overcharged (19V !), the leisure batteries weren't being charged at all. So I connected the positives together as an emergency measure, and lo and behold! everything went back to normal, with both being charged at 14.5V.

 

So am I to assume that the split charge system is faulty? I've searched diligently but cannot find a relay and I wouldn't know what a diode looked like. Anyone care to enlighten me? All the relevant wires disappear into a bulkhead and only reappear behind the control panel.

 

We had similar (although not as high as 19V! ) on Gamebird when we first got her.

One alternator, Adverc charge controller and diode splitter.

Despite what is generally believed, the volt drop across a diode DOES vary a bit wth current, which was the problem. When the cabin batteries were low, there was a bigger volt drop across their diode, so the Adverc cranked up the alternator voltage to compensate. Starter battery was fairly fully charged , so not taking much current, so less of a volt drop across it's diode, resulting in 16V - 17V across the starter battery. If we'd had a larger alternator, starter battery volts might have been higher, I think.

 

Problem was solved when a relay fitted and the diodes ditched.

[Sir Nibble]

I also had an overcharging problem, which I assumed was due to the alternator controller, and described here When I was back to the boat recently, I started measuring things again, and found that while the starter battery was being overcharged (19V !), the leisure batteries weren't being charged at all. So I connected the positives together as an emergency measure, and lo and behold! everything went back to normal, with both being charged at 14.5V.

 

So am I to assume that the split charge system is faulty? I've searched diligently but cannot find a relay and I wouldn't know what a diode looked like. Anyone care to enlighten me? All the relevant wires disappear into a bulkhead and only reappear behind the control panel.

Sounds like you hae battery sensing off whichever set is "secondary" to the alternator. About the worst of both worlds.

[Mac of Cygnet]

Sounds like you hae battery sensing off whichever set is "secondary" to the alternator. About the worst of both worlds.

 

But nothing has changed! It's been fine for the past ten years and suddenly produced these symptoms in March.

[Just Heaven]

Sir Nibble's temporary fix is working well, but I'd like to get the regulator replaced. Currently at Whitchurch, can anyone recommend a boat electrics person in the Barbridge/Middlewich/Kidsgrove area that could supply and fit one for me?

Or failing that a supplier and I'll have a go at fitting it myself

Steve

[roland elsdon]

Any motor factor / alternator rebuilder will have a box of them. I carry 2 spare advec modified one and a standard one at all times, as I have had several fail it's a 127 alternator reg you need. To remove it and replace there are several tricks including using a paper clip or 2 mm Allen key to hold the brushes in place . You also may need a small socket for the bolts. But they may be screws. Course you could go into halfords buy an alternator and keep the old as a spare....