T-Pain Is On A Boat: Re: [Electric Boats] When good batteries go bad

Thursday, July 16, 2009

Re: [Electric Boats] When good batteries go bad

One of the reasons to not do that is that you end up with the good battery charging the bad one, the worse case scenario in terms of losses. As soon as the charger isn't keeping the bad one topped off the good one will start do to so, but obviously it won't be able to and they will both loose charge until they are depleted. That's one of the reasons for battery isolators. Two batteries that aren't exactly the same will self discharge faster when connected together than when disconnected.

-Tad

----- Original Message -----
From: "aweekdaysailor" <aweekdaysailor@yahoo.com>
To: electricboats@yahoogroups.com
Sent: Thursday, July 16, 2009 12:47:52 PM GMT -05:00 US/Canada Eastern
Subject: [Electric Boats] When good batteries go bad

OK, short of tossing 12 batteries...I am experimenting with selectively replacing bad batteries in my pack.

By "bad" I mean a battery that will accept a full charge, but discharges well in advance of the other batteries in the string (so...it's not a shorted cell which I think is an automatic toss, but rather likely plate degradation)

I have already tried de-sulfating - I can see improvement, but not enough.

My theory is...if I pair a new battery with the worst of the pack (in parallel) then that unit now acts like a medium-good battery in relation to the others (the good battery will be trying to continually charge the bad one during discharge - conversely during charge the good battery will be helping the charger see it's "full" and go into float). I think I still won't get the full pack amperage, but some "average" value determined by the weakest pair.

There are lots of warnings about not doing this - but no clear explanations.

Any battery gurus care to comment on the strategy?

I've split my 12 into 2 separate banks now - 1 bank of 4 batteries (all aged) and 1 of 8 (2ea in parallel for the above balancing). I'm using my old red Perko switch so I can combine or run each bank independent. This allows me to isolate and test "bad" batteries individually and re-shuffle the packs to find the proper balance.

Also...my chargers do not have an equalization setting. Short of buying one that does have one - is there another way to do an equalization? Maybe that can further help the weak batteries.

Am I doomed to visiting Walmarts return counter?

Thx

-Keith

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