Battery drain

[Sadlerfin]

This might be a silly question and I apologise in advance.
My recently aquired Bav 30 has two switches for the batteries, one domestic and one engine.

My question is when I'm sailing using instruments and nav lights with both switched on am I draining both batteries? Should I turn the engine battery off? I feel it should be left on in case of a MOB which would require an immediate engine start, but after a long journey would hate find a dead battery.

Thanks

Derek

[Symphony]

No. The two are entirely separate. All your instruments run from the domestic battery via the DC switch panel. The engine start battery only works the engine. The two banks are charged by the alternator via a splitter. You can leave the engine battery on all the time as it will be fully charged as a priority when you run the engine. Of course it may eventually die and some people fit an emergency parallel switch so that the engine can be started from the domestic bank.

[Nigel]

... the engine battery ... will be fully charged as a priority when you run the engine...

Probably not "as a priority"

[Kibo]

I always carry jump leads so I can always connect one set of batteries to the other. Much cheaper and more flexible than adding permanent parallel switches and one may need them for other emergencies too one day !

[Sadlerfin]

Some good info

Thanks