APC Back-UPS CS Replacement Batteries Make your APC Back-UPS CS run like new again with a replacement battery set from Power Pros. Genuine APC and BTI kits include all necessary cabling, connectors, and tray - no assembly required.  These battery kits are 100% compatible with APC ups systems and come with a full 1 year warranty (APC) or 18 month warranty (BTI). If you don't see your application listed, please give us a call at 1-888-330-2538 for expert assistance.     Model Battery BK350, BK500, BK500BLK RBC2