How to Calculate UPS Battery Backup Time?
By calculating with simple formula:
Backup Time (in hours) = Battery Capacity (in Ah) X Input voltage (V) / Total Load (in Watts)
Assume that you have an UPS/Inverter battery with 200 Ah of capacity and 12 V of input voltage. You have 5 lights, 2 fans and 1 wifi router,
Let’s calculate watts,
5 lights = 18 x 5 = 90 Watts
2 fans = 75 x 2 = 150 Watts
1 Wi-Fi router = 1×20 Watts = 20 Watts
So, the total load is : 90 + 150 + 20 = 260 Watts.
let’s apply all these values in the above formula.
Backup Time (in hours) = 200 x 12 / 260 = 9.2
So, your UPS/Inverter backup time is around 9.2 hours to keep your appliances power on.
But in real, battery efficiency is = 0.8
So, re-calculate with this formula :
Battery Capacity (in Ah) X Input voltage (V) X Battery Efficiency/ Total Load (in Watts)
So,
Backup Time (in hours) = 200 x 12 x 0.8 / 260 = 7.3
So, your UPS/Inverter backup time is around 7.3 hours to keep your appliances power on.
The above formula is for only one battery (12 volt)
IF YOU HAVE 2 BATTERIES (24 VOLT UPS)
IF your UPS is 24 volt UPS, (with 2 batteries)
then the formula is is :
Battery Capacity (in Ah) X Input voltage (V) X Number of Batteries X Battery Efficiency/ Total Load (in Watts)
let’s calculate with the same load,
Backup Time (in hours) = 200 x 12 x 2 X 0.8 / 260 = 14.7
So, your UPS/Inverter backup time is around 14.7 hours to keep your appliances power on.