Battery Warning Light/Alarm (B37)

[dawntreader]

I am getting intermittent red light/sound alarms from the console and the 'battery' light flashes. There is no set 'pattern' as to when the alarm comes on that I can recognise. It can come on as soon as the alternator kicks in and starts charging and then may persist or not come back for a hours.

The battery monitor (NASA BM1) shows that the voltage is fine and I do not appear to have a 'battery problem' as they perform as expected. I do have alternate charging from wind and solar but even with those isolated the alarm can sound.

Does anyone know what are the conditions for the alarm to activate?

Jim, Dawn Treader

[dawntreader]

Changed the oil - 'battery alarm' stopped. Thinking of buying a canoe 

[Viking]

Which engine do you have?

I have a Volvo Penta D2-75 and had a similar problem when the engine ran in idle (tick-over).
There turned out to be 2 problems:
1) the alternator was not functioning correctly - was replaced
This seemed to fix the problem, but only for a very short time ...
2) the MDI box was faulty and was replaced
That solved the problem for good.

[dawntreader]

thanks for your comment - glad I'm not alone. Engine is D1-30hp. Alarm is conspicuous by its absence since changing the oil and I have motored over 18 hours since then. I have removed and had the alternator thoroughly checked at an engineering workshop and it was pronounced 'healthy'. MDI box was on my list of 'suspects' but until I can check for good/bad readings I need to know what these are before attributing blame - hence my post.