Gene Kearns wrote:
On Mon, 13 Aug 2007 11:11:52 -0400, "Reginald P. Smithers III"
wrote:

Gene Kearns wrote:
On Mon, 13 Aug 2007 10:53:12 -0400, "Reginald P. Smithers III"
wrote:

Short Wave Sportfishing wrote:

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.
Tom,
When you switch it to "Both" on the A/B switch, are you just charging
both or are you running them in series?
Not as easy a question as you might think!

What is happening if the A/B Switch is set for "Both" and Battery "A"
has 11.5 Volts, Battery "B" has 9.5 Volts, and the engine is providing
12.5 Volts????

Now, imagine what is going on if Battery "B" has 9.5 Volts because it
has a weak cell.....
I have always thought Battery B would drain battery A to equalize the
voltage if they were not being charged, but if it was charging both
batteries, they would only charge up to about 13 volts and then the
charger turns off.

I always use Battery B for when I am at anchorage, but switch it to both
when I am ready to start the engine. I am using the rational that it
would take awhile for the B battery to drain the A battery and the
engine is always started in less than 30 sec from the time I switch the
perko to Both.

I was told whatever you do, don't switch the Perko switch when the
engine is running. Something about the end of the world as we know it.

A properly built A/B switch has a make-before-break feature. You don't
want the alternator to sense a really low voltage situation (break)
and go to *infinite* charge. Toast.......

So it would be the end of the world as we know it.