PoE UPS Battery Calculator

Size a battery bank for a UPS-backed PoE switch, including powered devices, the switch itself and any other protected equipment.

Required Wh = design load × runtime ÷ UPS efficiency × ageing allowance ÷ usable battery capacity

Use worst-case measured or manufacturer power figures. The result is a design estimate, not a substitute for the UPS manufacturer's runtime data or battery discharge curves.

Report details (optional)

Site name

Site reference / job number

Switch / UPS reference

Notes

Protected load

Total PoE device load (W)Cameras, readers, access points and other powered devices.

PoE switch base load (W)The switch's own consumption, excluding its PoE output.

Other protected load (W)NVR, router, fibre equipment or other UPS-backed devices.

Load / expansion margin (%)

Required backup runtime (hours)

UPS conversion efficiency (%)

Battery bank

Nominal battery bank voltage (V)

Battery usable-capacity preset

Custom usable capacity (%)Only used when the custom preset is selected.

Battery ageing margin (%)

Existing battery check (optional)

Check an existing battery bank?

Existing bank capacity (Ah)Use the bank Ah rating; series-connected batteries do not add Ah.

Using the result safely

Confirm the UPS supports the selected battery voltage, chemistry, capacity and charging current.
Use worst-case PoE loads, including heaters, infrared illumination, PTZ movement and startup demand.
Battery performance varies with temperature, discharge rate, age and manufacturer cut-off voltage.
For an AC UPS, compare this estimate with the manufacturer's runtime curve at the calculated design load.
Check that the UPS continuous and surge output ratings exceed the complete protected load.

First establish device demand with the PoE Budget Calculator, then read the wiki guidance on Power over Ethernet, network switches and emergency power backup systems.