Backup Time (in hours) = Battery Capacity (in Ah) X Input voltage (V) / Total Load (in Watts)
You can use the following simple formula:
Backup Time (in hours) = Battery Capacity (in Ah) X Input voltage (V) / Total Load (in Watts)
Let us assume that you have an inverter battery with 150 Ah of capacity and 12 V of input voltage. You want 3 tube lights, 2 fans, and 1 Wi-Fi router to run on that battery. So, what will be your inverter battery backup time, and how long will your appliances run in this specific case? Let’s find out.
Taking your inputs into consideration, you can calculate your total load, like:
3 tube lights = 40 x 3 = 120 Watts
2 fans = 75 x 2 = 150 Watts
1 Wi-Fi router = 1×20 Watts = 20 Watts
So, the total load in your case is 120 + 150 + 20 = 290 Watts.
Now, let us apply all these values in the above-said battery backup time formula.
Backup Time (in hours) = 150 x 12 / 290 = 6.2
So, your inverter battery will last around 6.2 hours to keep your needed appliances running.
Battery Capacity and Inverter Backup Time:
Does the backup time depend on the capacity of the battery? Of course, it does!
Let us keep all the values same other than the battery capacity. Now, let us figure out the inverter backup time for both small and large battery capacities. Using a UPS backup calculator can also help.
If the battery capacity is 110Ah:
Backup Time (in hours) = 110 x 12 / 290 = 4.5 hours
In this case, you will get an inverter backup of only 4.5 hours.
If the battery capacity is 220Ah:
Backup Time (in hours) = 220 x 12 / 290 = 9.1 hours
In this scenario, you will get an inverter backup of nearly 9.1 hours.
So, you can safely assume that your battery’s capacity plays a vital role in your inverter backup. Or the higher the battery capacity, the greater will be the inverter backup time.
The above calculation is perfect on paper. But in a real-time scenario, the inverter’s efficiency plays a vital role in its backup time. The better the inverter efficiency, the more the backup time.
