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

Short Wave Sportfishing

On Mon, 13 Aug 2007 04:37:04 -0000, wrote:

How should I approach this?

First off, do not wire the batteries in series - that doubles the
voltage. Second, do not wire the batteries in parallel - that doubles
the amperage available. An A/B switch is a potential solution but
that has problems also.

You need to determine what the charging rate is for your alternator.
As Rob said, it should be somewhere around 6 to 8 amps. I don't think
you mentioned the size of the engine - that would help a little.

That said, I would put put everything on a deep cycle, group 27/28
marine/rv battery and keep the second battery on an A/B switch as
insurance.

That would be my solution - not the best, but the easiest.