I read a very interesting Marine Accident Investigation Branch (MAIB) report a while ago which I remembered again just now, about a fatal man overboard from CV30 - a Clipper round the world race boat. One thing I remember is this ingenious hack in section 1.8.2 about generator failure:

“one of the crew on board managed to dismantle an old battery and used the carbon electrodes to fashion new brushes for the generator”

I guess it would have been a zinc carbon AA(A) cell, which has a carbon rod down the middle.