How to put batteries in an APC SYBT5 Battery pack

Note there is an EEPROM on the small PCB.
If the UPS notices the cells are bad, it will set this EEPROM to flag a bad battery state. Even if you put new batteries in the tray, it will not clear this flag.

If you order the cell trays from us at UPS-Trader.co.uk we make sure these EEPROMS are set to a good battery state :)