Estimated Time of Discharge and Charging a Battery

A simple but useful calculation is the estimated time of discharge and charging a battery. So, first you need to know the battery capacity that is expressed in Ah. The time of discharge is given by de expression Capacity (Ah)/Consumer Load (A).

If we have a load with 3W and the battery give 4,5V, the consumer load is 0,666A. If the capacity of battery is 3.600mAh, so the time of discharge is 3.600mAh/666mA = 5,4h.

The same expression is used to calculate the time to charging but we need used the current used to load the battery instead the current of load.