Optimization of charge parameters for lead–acid batteries used in photovoltaic systems

The lead–acid batteries used in the photovoltaic (PV) systems are subjected to penalizing operating conditions. The recharge is badly controlled since it depends on the weather conditions. These particular operating conditions induce unusual degradations of the active material compared to more traditional applications like SLI batteries. Consequently, when used in PV applications, lead–acid batteries show a shorter lifetime than they could reach. The management of the recharge of the photovoltaic lead–acid batteries is a major issue for the optimization of their lifetime. Today, complex methods of end of recharge, such as complements of recharge using current pulses, are increasingly widespread. Many parameters can be adjusted (frequency, duty cycle, voltage threshold for beginning the pulsed phase …) but no reliable data are available in the literature. The study that follows deals with the experimental optimization of these various parameters (under well defined operating conditions). In the same time, a specific software has been developed in our laboratory and helps to understand why these pulses increase the charge acceptance of the lead–acid battery.