boat battery run down

chuckg5 · #1 (**permalink**) 07-01-2007

we have a nice 42'er grounded on our farm right now. Last october i bought two wal mart boat batteries, the big ones Maxxi, i think they're called.
i keep a battery charger on one of them an run the interior lites, radio an such most days. a few weeks ago the 'house' battery on the charger is running down, low voltage 11.2 , the charger shows 'fully charged', the sephic (sp?) gravity meter shows almost dead. why would the darn thing charge? the other battery is hooked up to the main bilge pump ( for rain water purposes) and is just fine 12.8 vlts after all these months.
have I sulfated the 1st battery to death? even with a trickle charger , at the maintainer setting then shifting it over to regular charge, doesn't seem to matter.
thanks!

camaraderie · #2 (**permalink**) 07-01-2007

You haven't said...but my guess is that these are wet cell batteries and all the water is gone from one or more of the cells.
Alternatively it is quite possible to sulphate a bettery under a constant inadequate charging regimen in 6 months. It may also be a defective cell which has brought the entire battery down with it. You probably can get a warranty adjustment at wal-mart but....

Better plan would be to RUN the batteries down to 12.1 Volts (1/2 charged) AT REST AFTER AN HOUR WITH NO LOAD ON THEM....then put them under a charge of 14.4 Volts (assuming wet cells) for enough time based on your CHARGER AMP RATING to put them at about 80% full. Then reduce voltage to 13.8 volts ...then finally get to the trickle charge.
Better yet...get a real 3 stage charger since you'll need it once the boat comes off the farm and run the battery down to 50% at least once every couple of weeks and let the charger do its' job. If you use wet cells...a charger with an EQ setting would be even better.

chuckg5 · #3 (**permalink**) 07-01-2007

Cam
thanks for the reply
yes, the Maxxi's are wet cell.
an yes, i'm returning it to walmart for an exchange
i'll have to pay more attention on how they are being charged
its odd, thou , the darn car battery charger I have shows green lite- fully charged- not good info
you do great work, Cam
thanks for being here.
chuck

chuckg5 · #4 (**permalink**) 07-01-2007

i've always checked the water in the cells
it never went below the plates but i did keep them topped off
probably just a poor battery purchase
need multiple batteries out on the water
must keep bilge pumps working!

camaraderie · #5 (**permalink**) 07-01-2007

My pleasure Chuck. BTW we have friends on a Vag47 that have been in the Caribe for the last several years. Good cruising boats & pretty lines..I'm sure yours will be worth all the elbow grease in the end!! Good luck.

sailingdog · #6 (**permalink**) 07-02-2007

Quote:

Originally Posted by chuckg5

i've always checked the water in the cells
it never went below the plates but i did keep them topped off
probably just a poor battery purchase
need multiple batteries out on the water
must keep bilge pumps working!

Nah, just a automotive charger trying to do the work of a three-stage marine charger. You really need to get a three-or-four stage intelligent charger.