Formula for Backup Time Calculation:
Backup Time = Battery Capacity (in Ah) * Battery Voltage (in V) * Battery Efficiency (in %) / Connected Load (in W/h)
For instance:
Scenario 1: Lead Acid Battery If utilizing a lead acid battery with a capacity ranging from 80Ah to 200Ah, the following example illustrates the calculation using a popular 150Ah battery. For standardization, a 400-watt home load is considered, resulting in a connected load of 400 watts per hour. The backup time can be calculated as follows:
Backup Time = 150Ah * 12V * 0.75 / 400 W
markdown = 1350 W / 400 W
= 3.3 hrs.
Note: Lead acid battery efficiency typically ranges from approximately 70% to 75%.
Thus, running 400-watt home loads on a 150Ah inverter battery provides approximately 3 hours and 30 minutes of backup time. Based on the required backup duration, suitable battery capacity can be chosen.
Scenario 2: Lithium Battery For a lithium battery option, such as a 100Ah, 12.8V variant, the backup time calculation remains consistent with the aforementioned formula. Using the same parameters, the backup time for a lithium battery is determined as follows:
Backup Time = 100Ah * 12.8V * 0.98 / 400 W
markdown = 1254 W / 400 W
= 3.13 hrs.
Note: Lithium battery efficiency typically ranges from approximately 95% to 98%.
Consequently, running 400-watt home loads on a 100Ah lithium inverter battery provides approximately 3 hours and 15 minutes of backup time. Similar calculations can be applied to determine the backup time for other lithium battery models, such as the CAML 100, 5kWh variant.