Battery charging occurs at 13.8 to 14.1 volts give or take and is battery
type dependent. If your charger holds that voltage even though the amps
drop to minimal it will boil the water from the batteries. The new chargers
of today will drop the voltage back to 12.9 (or so) when the amps drop off
for "float".

I had an old West Marine charger (no "float") years ago that liked to cook
batteries. I had to add water monthly. I installed a timer on the plug
that cycled the charger on for about 1 hour per day. This solved the
problem but a better charger was the real trick. I highly recommend one
with "bulk", "Accept", and "float" capabilities.

Five years on a set of batteries is good. I am kind of jealous.

"Woodchuck" wrote in message
...
5 year old batteries, you done well!

"Wklkj" wrote in message
...
I have a cruiser with 3 - 12 volt batteries installed, the boat is twin
screw
and has 2 battery switches (1,2,all,off) type, and finally a 30 amp
battery
charger with terminals for all 3 batteries.

I always leave the charger on at the dock with shorepower but the past
couple
of weeks I have 'cooked' 2 of the 3 batteries (maintenance free, probably
5
years old). Friends on the dock are guessing that the battery charger is
broken. Although it still charges fine, they suspect that it doesn't
shut
off
when the batteries are fully charged, causing them to boil over and
eventually
dry up.

Here's my questions:

I just purchased 3 'dual purpose' Exide brand marine batteries that are
not
maintenance free so I can pop the caps and see if there's water in the
cells.
Do you think I can continue to use the original battery charger and just
watch
to see that they don't boil dry?

A new charger which will charge 3 batteries is around $300. (ouch). I
can get
a guest charger (2611) for $100 that is 10 amp on 2 circuits, for 2
batteries.
What will happen if I connect 2 batteries to one of the terminals in the
charger? Will that work or will I break something?

My other thought is to only hook up 2 of the 3 batteries to the new
charger and
leave the 3rd one to charge when the engine is running, but not use that
3rd
battery for any accessories. This seems like a logical approach to me.

Any comments?

Thanks.