Batteries are the storage devices for power. The utility power is in AC form and batteries store it in DC form. The charger section of UPS facilitates this. There are generally three types of batteries, namely, Automotive, Tubular and SMF (Sealed Maintenance Free). Automotive batteries are used for vehicles where discharge is deep for a short duration. Tubular batteries are designed for deep discharge for long durations such as in the case of UPS applications. Both Tubular and SMF are used for all industrial uses including UPS.

Battery is the main storage power for any UPS system. Each UPS may be designed with a specific battery voltage. Batteries are available in different voltages and different capacities. Batteries are available in different voltage ratings such as 2V, 6V, 12V, etc of which 12V is the most popular of all the lot. Suppose a UPS is designed with 120V DC battery voltage. it requires at least 10 nos of 12V batteries to work the system. The size of each of these batteries determine the backup time available after power failure. Battery capacity is measured as AH(Ampere Hour) and will vary from say 1AH to 300AH. Generally the bigger the battery, more is the AH it will have and gives longer back up.