How to match the discharge time of commercial UPS with the battery specifications (series/parallel)?

How to match the discharge time of commercial UPS with the battery specifications (series/parallel)?

The matching of the discharge time of commercial UPS with the battery specifications (series/parallel) mainly depends on the following factors:

• The power of UPS

• The discharge time requirement of UPS

• The capacity of the battery

• The voltage of the battery

Calculation formula

The discharge time of UPS can be calculated according to the following formula:

Discharge time = Battery capacity / UPS power * Battery efficiency

Where:

• Battery capacity: Unit is ampere hour (Ah)

• UPS power: Unit is watt (W)

• Battery efficiency: Generally take 0.8

Series/parallel connection

The series/parallel connection of batteries will affect the capacity and voltage of batteries.

• Series connection: The voltage of the battery will increase, and the capacity will remain unchanged.

• Parallel connection: The capacity of the battery will increase, and the voltage will remain unchanged.

Example

Assume that the power of a UPS is 700W, the discharge time requirement is 10 minutes, and the cut-off voltage of the battery is 1.67V/CELL.

Calculation steps

1. Calculate the battery capacity:

Battery capacity = UPS power * Discharge time / Battery efficiency
= 700W * 10 minutes / 0.8
= 875Wh