"Speedy Jim" wrote in message
I have 2 deep-cycle in parallel. They will run the fridge
for a couple of days. The oil furnace I ran for shorter periods
so I don't have a good figure.

Yes, you could charge off the car alternator. Might want to
put an ammeter in the circuit to limit load on the alt to some
reasonable figure/

Jim

That is longer than I would have though possible. Thanks.