Many reviews criticize the APC branded replacement batteries for failing prematurely, and the 3rd party knock-offs are often a joke

Good unit, good batteries, good history

Very well reputed maintenance-free AGM batteries

You have to tell the UPS that there's more standby time or the unit will shutdown before the batteries are exhausted

The BatteriesI went out and bought two 12-volt Optima Blue Top batteries (Optima Batteries 8052-

The batteries failed way early

This smart battery backup has served our office well.

Here are a couple of example links to the batteries that failed prematurely here UPSBatteryCenter Compatible Battery Pack for APC Smart-