The operating time of the inverter depends on the battery capacity and load power. Here we first introduce the resistive load, which is the electrical appliances that have no peak power when starting. The standard capacity of the battery is in ampere-hours(AH). The ampere-hours(AH)means: the maximum discharge capacity of the battery within one hour. For example, if a battery is nominally 100AH, it means that it can continuously output a maximum current of 100A within one hour.
The battery can not be fully discharged, if it is fully discharged, the battery will be scrapped, so the battery has a memory function, and there is always 20% of the power in the battery. so 0.8, the battery discharge coefficient (constant), is the actual power that the battery can work. In addition, the inverter generally has a conversion regarding efficiency, the general working efficiency of sine wave inverters is around 80%-90%, so here we choose 0.9, inverter conversion efficiency
Therefore, the time it takes for the battery to do work on the resistive load through the inverter:
battery capacity * battery voltage * 0.8 * 0.9 / load wattage = working time (hours)
For example, Calculate the time that a 110W bulb can work with a 12V 100AH battery.
Working time = 100(AH)X12(V)X0.8X0.9/110(W)=7.85 hours)
12V: the battery voltage
100(AH) :battery capacity
0.8: battery discharge coefficient (constant)
0.9:Inverter conversion efficiency
110(W) :bulb nominal power
It is worth noting that the starting power of inductive loads such as air conditioners, washing machines, water pumps, and power tools may be 3-7 times the working power, or even higher, such as a refrigerator, its starting power may be 10 times the working power, so the inductive load needs to be divided by 3-10 according to the load condition.
The following is the formula for calculating the working hours of an inductive load
battery capacity * battery voltage * 0.8 * 0.9 / load power / 3-10 = working time (hours).
For example, Calculate the time that a 110W refrigerator can work with a 12V 100AH battery.
Working time = 100 (AH) X 12 (V) X 0.8 X 0. 9/110(W)/10=0.785(hour)
12V: the battery voltage
100(AH) :battery capacity
0.8: battery discharge coefficient (constant)
0.9:Inverter conversion efficiency
110(W) :refrigerator nominal power
10: It is the ratio of the peak power of the refrigerator to the rated power.
That is, a 12V 100AH battery can only support a 110V refrigerator for about 47 minutes, however, this is only a theoretical calculation. In actuality, a 12V 100AH battery cannot support the startup of a 110W refrigerator. Inverters usually have a low-voltage protection function,when the battery capacity is not able to support the load, the inverter will be in a low-voltage protection state. Usually, this can be solved by increasing the battery capacity, that is, by paralleling the battery cells to increase the battery capacity.