APC Replacement Battery Cartridge #115 - UPS battery - 1 x lead acid - black - for Smart-UPS X 1500 Rack/Tower LCD, 1500VA Rack/Tower LCD (APCRBC115) at TigerDirect.com
APC Back - UPS RS1500 - Battery Replacement - YouTube
Replacement UPS Battery Set for PW9120-1500 Eaton Powerware - (4 batteries - 12V 7.5AH)
DIY APC Smart UPS 1500 Battery Replacement Hot Swap - Not Sealed