Shared Knowledge
"APC RS900 UPS - Buy Used?"
21 February 2014
Summary: an APC RS900 can look like a good dead as good capacity and from APC BUT if you buying one, get one with new battery pack and one guaranteed to work by seller.
Background:
You need a uninterruptable power supply (UPS) for some device.
You look around at new and one with any sort of volt-amps or watts supported cost $$ or even $$$.
You see that an APC RS900 can be had pretty cheaply: from APC and good amount of volt-amps.
Beware:
(1) An APC RS900 will not power up if it does not have a good battery pack.
(2) So to even get an RS900 to power up you have committed to a new battery pack $50 - $80 more.
(3) An APC RS900 with a valid battery pack will pass a power-on self test and still not be charging the battery pack correctly.
(4) The only way to setup and properly test the RS900 is via a special APC signal cable ($10 more) and a personal computer.
(5) APC does not service RS900 anymore
(6) I could find no Internet-based service that will repair the RS900.
(7) I could find no schematic for the RS900. Perhaps if you are a good analog circuit guy, you could fix, maybe.
Bottom line:
Only buy an APC RS900 that has a new battery pack, an APC signal cable and that is guaranteed to work by the seller.
Otherwise, you could spend a lot of money to find you have a bum RS900.