IMO, any type of LA lead/acid battery that's neglected for years is
unrecoverable. The plate surfaces are likely to start to become sulfated as
soon as a battery is left at a low voltage level/dead.
From what I've read, LA batteries with liquid electrolyte can sometimes be
desulfated, but batteries with gel electrolyte can not.
Desulfating consists of high frequency (10 kHz, maybe higher) current pulses
that are said to remove the sulfated coating, which is then held in
suspension, or removed by replacing the liquid electrolyte.
If the batteries were left in a low state/dead for only weeks (or possibly a
month), but wouldn't take a charge, there is a variac and rectifier
improvised technique that often works to get a LA batterys' condition to a
point where it can be properly charged.
If some liquid electrolyte batteries were an exceptionally high grade of
batteries, they may be recoverable by desulfating if they had been left at a
low voltage level/dead for a couple of months, but I highly doubt that any
that have been completely dead in excess of 6 months would be recoverable.
There is a lot of battery info online, some of it factual and some related
to fluke situations. Fluke being a battery that was assumed to be fully
recovered, performs badly within a short time, like the car battery that
starts the engine fine, but suddenly won't on a cold day.
The serious non-professional battery users are the folks that live
off-the-grid. These folks strive to use and maintain batteries as
effectively as possible.
I'm not aware of any quick, easy evaluation methods that will accurately
indicate a battery's watt-hour capacity or potential reliability, unless the
battery is in very good condition, and properly maintained.
I suspect that when a LA battery (and most other types) has been left in
dead condition for any amount of time, it's performance capability and
reliability are greatly diminished.
What Wayne suggests about being careful is wise. Many improvised/hack
methods aren't particularly safe, and many methods probably shouldn't be
left unattended.
--
WB
..........
metalworking projects
www.kwagmire.com/metal_proj.html
"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??