I found this note from Garland interesting.

I know that, not too long ago, I charged a suspect
battery to 14V+ and checking soon after at 12 volts
expected it to be good.
But it was whacked, and I discarded it.

So I am realising, I did not expect the charging volts to
be reflected in an overvolt reading a day later.
But I will, in future!

Brian Whatcott

On Sat, 24 Jan 2004 20:07:55 -0500, "Garland Gray II"
wrote:

A battery test in an old Ample Power catalog was to charge to 14.4 volts and
hold it there for an hour. Let it rest overnight, and then retest.
12.8 v & higher=good
12.6 to 12.7v=marginal
12.4 to 12.6v=very poor
less than 12.4 v=worthless

"Rick & Linda Bernard" wrote in message
...
Anyone have a good way of testing 12V deep cycle batteries?

What I was figuring on doing was using a 50watt 12V lightbulb and
measuring
voltage with time. The only problem is that this may take a few hours.