Re: Battery Back-up Hack Question
APC uses SLA (Sealed Lead Acid) batteries from various manufacturers. If you still have the old batteries (a UPS this size will have multiple batteries in series, parallel, or a combination of the two), you can peal off the APC sticker from the batteries. This will reveal the actual manufacturers markings. You want to know the voltage (probably 12V) and the amp hours (ah) of the original batteries.
You can then rebuild the battery pack with new batteries of the same specs. A higher amp hour battery should work with no problems so long as it's physically the same size and is the same voltage.
Exactly what model is this? A Smart-UPS, Back-UPS, or ??? A Google of the actual part number (look for a sticker with part number and serial number) should tell you what the "RBC" number for the APC replacement is. Then google the RBC number and you'll find the generic replacement batteries that are acceptable alternatives.
Most likely, the batteries have a wiring harness that will need to be transferred to the new battery (not necessary when using the actual RBC replacement, but needed if replacing with generic batteries).
APC recommends replacing UPS batteries after 3 years, but my experience with them says they are usually good for around 5 - 6 years. I have replaced about 75 SLA batteries in APC UPS units over the last three years. As they fail, they tend to swell, particularly on the ends. Eventually the ends crack open and the acid leaks out. Not good when that happens. Generally, a new battery = UPS good as new, but about 1/10th of the units I deal with are not reliable, even with a new battery, after about five years. We had one start melting (literally)...it stunk up the whole lobby. The wiring had shorted out on it...battery was the least of its problems. Others fail because it improperly reads incoming voltage, triggering it to switch to battery do to a non-existent brownout.