On Tue, 19 May 2009 21:10:17 -0500, "Don Young"
wrote:


"RoyJ" wrote in message
news
I've got a couple of battery packs in the storeroom that need some
attention. Both have been stored for periods of time, need to see if they
are usable or get them out to the scrap dealer.

Pack #1 is a set of 6 deep discharge 6 volt batteries in a mobile cart.
Charger for it was trash, had fried circuit board. Unit has been sitting
for multiple (4+??)years. I'm betting that they are completely discharged
and that there are a bunch of shorted out cells in the set. Cells were low
on water, topped them off with distilled water. I think I will take a
regulated DC power supply, see what voltage it starts to take current.
From my reading, a functioning but fully discharged cell should start
taking current at 1.98 volt and fully charged at 2.10 volt. So a 6 volt
battery with one shorted cell should start at around 4 volts then go up to
4.2 volts at full charge. Any other suggestions on how to test, deal,
whatever?

Pack #2 is actually 3 packs of 19 each 12 volt gel pack batteries (228
volts per pack, there may be a couple batteries missing). It came from a
huge battery backup for a computer center. I suspect it was set up to
provide 3 phase 208 power. This bunch has been sitting for about a year
with no attention. These are gel pack (??), about the same size as a
standard auto battery, fully sealed, and sit on their sides. How do I
test? What should I do to keep them alive and well for future projects??

You have received a lot of good information and the only thing I can add is
to be sure to watch the electrolyte level carefully. If the batteries start
to take a charge and/or warm up, the level can rise quite a bit and this can
result in overflow. It is best to start with the level just at the top of
the plates.

Don Young



Survival of the 6V batteries after 4 years uncharged is
pretty unlikely. They are likely to be deeply sulphated and
refuse to accept a charge at anything like the usual max of
2.5v/cell. Less severe cases can sometimes be partially rescued
by prolonged low current overvoltage charging until it starts to
accept charge at less than 2.5V/cell but the results are seldom
worth the hassle.

Chances are much better with the gel pack batteries.
Dependent on local ambient temperature these happily hold their
charge for a year or more and just need a freshening charge
before putting into service. In normal use as backup batteries on
permanent float charge they seem to last about 5 years but many
organisation routinely replace them at 3 years or less. Stored,
charged, at reasonably low temperatures the life can be very long
indeeed. I keep a few 12v Yuasa batteries in a domestic fridge
when I am not using them. These were rescued after their 3 year
float charge stint and and are still going strong after nearly 10
years.

Yuasa recommendation for freshening charge after long
storage is either 10 hours constant current at 0.1C or 24 hours
constant voltage at 2.4V/cell

Jim