I have an older APC UPC, and the battery appears to be dead. It appears to be a small, lead-acid 12 battery - is it possible to revive the battery?
It's certainly not worth it to replace it - a new battery, even a no-name, is about $50 shipped - a whole new UPS, with similar specs, is only $65.
The Battery University site is a good resource for various batteries.
How to restore and prolong lead-acid batteries and
Charging the lead-acid battery.
Another reference -- Alton's Battery Page.
But, I'd just replace them (like I have once with my APC).
A lead-acid battery that has sat for any period of time after complete discharge (more than a week) suffers from sulphation. Under normal operation, lead peroxide and lead are converted to lead sulphate while creating current flow. The lead sulphate mostly converts back to the original materials during the charge cycle. The small amount that doesn't is why lead acid batteries eventually fail.
When left set uncharged, lead sulphate converts to a more solid, crystalline state. The material produced is mostly incapable of being returned back to lead peroxide and lead.
You can play with pulse chargers on badly sulphated batteries, but it's mostly playing as you will never restore the battery to more than marginally useful capacity. The pulse charging also can cause material to spall off the plates, eventually shorting one of the cells.
Float charge or charge once a month to keep lead-acid batteries operational and prevent hard sulphation. In other words, once you've placed a UPS in operation, keep it plugged in on a power strip and let it power up for a day every couple of weeks during its 3-4 year battery life.
And if there are bulges, you have a shorted cell which is causing overcharge in the remaining cells. One or more cells are out of commission, the battery will never produce full power and probably won't run the UPS during power failure. Replace immediately or pull the battery, recycle it and mark the UPS as being out of commission till the battery is replaced.
NOTE: There are vendors out there that sell fully compatible batteries for a lot less than the original manufacturer sells them for. Most of the time, you will find they're the same exact battery model and manufacturer as the OEM battery.
If the battery replacement price isn't right, get a new UPS, the new one will be more efficient and the surge protection circuitry will be fresh and ready to protect your equipment than the old one anyway.
you can try to revive a Lead-Acid with a pulse charger.
one of the great disadvantages of Lead-Acid batteries: they cannot be stored in a discharged condition (the cell voltage should never drop below 2.10V)
Get an cheapo car battery and hack the connector cable.
Let the vendor take the old battery.
