Size UPS batteries for a required runtime at a given load.
UPS batteries discharge at very high C-rates for short runtimes, which reduces effective capacity. Sizing must also allow for capacity loss as the batteries age toward replacement. A UPS that just meets its runtime when new will fail to do so within two years, which is why end-of-life derating is standard practice.
UPS Battery Size
Ah = load × minutes ÷ (60 × efficiency × voltage) ÷ (1 − end-of-life derate)
Ah = load × minutes ÷ (60 × efficiency × voltage) ÷ (1 − end-of-life derate) UPS batteries discharge at very high C-rates for short runtimes, which reduces effective capacity. Sizing must also allow for capacity loss as the batteries age toward replacement.
A UPS that just meets its runtime when new will fail to do so within two years, which is why end-of-life derating is standard practice.
This calculator takes 5 inputs: Load, Required runtime, Battery string voltage, Inverter efficiency, End-of-life capacity derating. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.