How often does a UPS battery need changing?

The battery is a small office UPS system or one designed for domestic applications will be a 5year design life battery that will require replacement within 3-4 years of installation. The life of a UPS battery is temperature dependent and the recommended ambient is 20-25˚C. If a UPS battery has aged and exceeded its working life, its DC voltage can collapse rapidly on mains power supply failure leading to a load crash. Most small UPS systems offer user-replaceable batteries which can be supplied as replacement UPS battery kits.