Depth of discharge
How much of a battery you can use without shortening its life. Plan on about 50% for lead-acid and 80 to 90% for lithium (LiFePO4).
UPS battery runtime calculator
See how long a battery bank keeps your tower or router up through a power cut, or the capacity a target runtime needs. Nothing you type is sent anywhere.
W
Ah
%
%
h
Estimated runtime5 h 6 min
12 V × 100 Ah × 1 × 50% × 85% ÷ 100 W = 5.1 h
- Battery bank
- 1,200 Wh
- Usable at the load
- 510 WhAfter depth of discharge and inverter losses.
- Capacity for 8 h
- 156.9 AhPer battery, with 1 at 12 V.
How the runtime is worked out
The energy the bank can safely give, less what the inverter loses, divided by the load.
Inverter efficiency
An inverter turns some of the battery's energy into heat. 85% is typical; a router fed DC straight from the battery skips that loss.
Load
Add up the watts of everything on the UPS: router, switch, radios and ONT. A rated figure is a maximum, so a measured one gives a truer runtime.
Leave headroom
Batteries lose capacity with age, heat and fast discharge. Treat the answer as a best case and size for a longer cut than you expect.