A seal lead-acid battery charger for prolonging battery lifetime using superimposed pulse frequency technique

A multilevel converter charger using superimposed pulse frequency technique for prolonging lead-acid battery lifetime is developed in this paper. The proposed state of charge is divided into three states: superimposed pulse frequency (SPF) charge, constant current (CC) charge and constant voltage (CV) charge. SPF is charging state for rejuvenating a deteriorated battery due to sulfation at the plates. In this state, the pulse frequency of voltage output will vary from 100 Hz to 1 kHz to scan for mechanical resonance. A dc to dc multilevel converter is applied to generate the superimposed pulse frequency. The mechanical resonance at the plates and the sulfation reasons are also studied. The simulation and experiment are also validated using the proposed charging technique. The simulation and experimental results suggest that the proposed multilevel converter charger can rejuvenate the voltage terminal of the battery even though the terminal voltage had dropped to less than 20% of full SOC which is normally considered as a worn-out battery. Also, the charging efficiency can be improved by using the proposed charging technique with a combination of the three states of charge.