Battery kit for APC Back UPS Pro BR 900 replaces APCRBC164
User manual APC Back-UPS 550 (English - 2 pages)
APC Power-Saving Back-UPS Pro 550, 550VA, LCD - APC Croatia
Powery GEL battery for UPS APC Power Saving Back-UPS Pro 550 9Ah 12V, 12V, 9Ah/108Wh, Lead-Acid battery, rechargeable, 151mm x 65mm x 94mm, 100% Compatible. New - AliExpress Consumer Electronics