said by wallstreet128:
can we buy a replacement battery online and what is the model #?
I bought this replacement in March 2011 (actually 3 since it's the same battery for my other UPSs), and have no regrets. I've really exercised the one in the FiOS BBU due to my system testing.
APC calls it a RBC2. Make sure you get a battery with F2 0.25 inch terminals. F1 is 0.187" and is not the correct size terminals.
While you can find lots of sellers, I'd suggest you go straight to a high volume battery vendor to assure you get product with short lead times. Sometimes a battery will sit on a shelf too long resulting in a shorter life.