Formula: Lead acid Battery life = (Battery capacity Wh × (85%) × inverter efficiency (90%), if running AC load) ÷ (Output load in watts). Let’s suppose, why non of the above methods are 100% accurate? I won't go in-depth about the discharging mechanism of a lead-acid battery.
The lead-acid battery has a nominal voltage of about 2v, it can vary from 1.8v at loaded at full discharge to 2.40v in an open circuit at full charge. The calculation of charging voltage can be done with voltage 2.40v/cell. 12v lead acid battery can be made from 6 cells connected in series.
The faster you discharge a lead acid battery the less energy you get (C-rating) Recommended discharge rate (C-rating) for lead acid batteries is between 0.2C (5h) to 0.05C (20h). Look at the manufacturer’s specs sheet to be sure. Formula to calculate the c-rating: C-rating (hour) = 1 ÷ C
The Charging begins when the Charger is connected at the positive and negative terminal. the lead-acid battery converts the lead sulfate (PbSO 4) at the negative electrode to lead (Pb) and At the positive terminal, the reaction converts the lead sulfate (PbSO 4) to lead oxide. The chemical reactions revers from discharging process
If we want a more accurate estimation of a battery’s charge time, we can include charge efficiency in the previous formula (battery capacity and charging current formula): battery charge time = battery capacity ÷ (charge efficiency x charge current) As with before, when the battery size is in Ah, the charge current should be in A.
Generally, battery life is calculated based on the current rating in Milliampere (mA) and the capacity of the battery in Milliampere Hours (mAh). The battery life can be calculated from the input current rating of the battery and the load current of the circuit. Battery life will be high when the load current is low and vice versa.