Development of a simplified method for the determination of ampere-hour capacity of lead-acid battery

Selection of the optimum level of current for charging and discharging operations is an important factor for the performance of lead-acid batteries in PV application. Realizing this situation, an experimental study was carried out to determine the performance of battery under different charging and discharging current. The battery was charged at an input current of 6, 12, and 18 A, whereas under these input charging currents the battery was discharged at constant loads of 5.7, 11.4, and 17.1 A. Then algebraic equations for the determination of battery ampere-hour capacity, in relation with state of charge, were formulated with the help of MATLAB software. The proposed model provides the battery output directly without going through the calculation of constant unknowns and battery ampere-hour capacity. It is different from previous models, which only evaluate the battery ampere-hour capacities with the help of already calculated battery ampere-hour capacities and other battery parameters from the same battery. During the study, it was found that the rate of charge and discharge affected the duration of charge and discharge as well as battery ampere-hour capacity. When the rate is increased, the number of ampere hours was decreased along with the battery operational time duration. The developed model equations were validated with ours as well as other researcher's measured values; the corresponding values were much closer when the values of state of charge were at the range of 100-90%. This study may be useful to understand the energy storage within a PV system and to select the optimum level of current, which consequently lengthens the life of the battery and improves the overall performance of a Photovoltaic panel (PV) system.