On Sat, 16 Oct 2010 09:35:29 -0400, Wayne.B
wrote:

Our house batts have not done nearly as well since we are now on our
3rd set in 6 years. The latest was installed last year before our 6
month Caribbean cruise and they show signs of doing better than
previously but there are reasons for that. We are now using Trojan
T-145s instead of T-105s, and I'm being really, really careful with
them. The first set was from Sam's Club and they were half dead after
just 6 months of liveaboard cruising but I'm sure some of that was my
fault.

Written with a smiling tone of write....

It does sound like you are doing something wrong. They should last
much longer. Maybe some rambling about the care and feeding...

The quickest way to destroy is to allow the electrolyte to get below
the top of the plates.

Number 2 is to consistantly overcharge. A possibility here is the
alternator. Another that I've seen do the job is a non-automatic AC
charger or an automatic one that is not cutting off, or cutting off at
too high a voltage. I had one that suddenly upped its cutoff voltage
to the point it would rarely cut off. It's now a mini fish reef.
Another battery murderer are solar panels with no regulator.

Number 3 is periods without recharging. It's best to recharge within
24 hours, if possible. One scenero is not using the boat for a while
and not using an automatic charger. The batteries will of course
self-dischagre.

Number 4 is not doing an equalizing charge regularly. This is like
Number 3 in that some of the cells will wind up at a lower charge and
those cells tend to be more and more discharged as time goes on. This
is also a reason to change both of the batteries in a series bank when
one fails. The idea to to match the series pairs as closely as
possible. It's not necessary to match on the parallel side. You can
mix those up any way you want, even to sticking a 12V, 100 AH battery
in there with no harm.

Note that if one cell on one battery is very much more discharged or
"bad", the rest of the pairs will be constantly "charging" that pair.
This results in ruining the other battery of the pair from constantly
"overcharging", and has occasionally resulted in the "bad" cell
actually getting a reverse charge (swapping + and - poles).




My quest now is for an alternator that can recharge them without
toasting itself in short order. Meanwhile I have to be careful to
only recharge one bank (4 batts) at a time.

Do you have temperature sensors hooked to the regulator? That's a very
good idea on a high-output alternator. Another "battery saver". Also
be aware that charging at more than C/10 will shorten the life a bit,
and of course like everything else battery, the higher the charge rate
the more effect.

Hope this is some food for thought.

Rick