BoatBanter.com - View Single Post - Battery question - hooking two batteries (marine and car/truck) together

trainfan1

wrote:
Okay - I'm new to boating, just bought my first. The guy I bought it
from has two batteries in the boat - a deep-cycle marine battery for
the starter, and a regular car and truck battery for the tilt motor,
lights, radio, etc. (both are 12 volt). The marine battery charges
itself from the magnets, but right now, the car battery just runs
itself down and has to be recharged frequently.

This doesn't seem efficient. Can I hook the batteries in together so
that the magnets are charging both at the same time? Or is it bad to
hook a marine and car/truck battery together? If I understand
batteries (and I'm not sure that I do!) I could connect the positive
terminal of the marine to the negative of the car/truck and that'd do
it. Is that right? Or would that screw with the voltage?

How should I approach this?

Matt

An A/B switch is one solution, but just the start of the work ahead of
you. A battery isolator is a likely candidate for what you have.

The starting & trim should be on the automotive type battery(which
really should be a marine cranking battery), the accessories(lights,
radio, etc.) should be on the deep cycle battery.

All this assuming you have better than a 4 or 6 amp outboard alternator.

You have some reading & research to do.

Rob