Fast Battery Charger for High Power LiFePO 4 Cells

A fast battery charger for high power nanophosphate ANR26650 commercial cells is presented. The protocol designed for the tested high power LiFePO 4 reduces the charging time by a factor of three with respect to standard charge, without perturbing cell performance throughout long-term cycling. The charging protocol consists of a two-stage constant current followed by a time-fixed constant voltage stage. A two-phase LCpCs resonant converter with synchronous current doubler rectifier is designed to obtain the proposed charging profile at a constant switching frequency maintaining the efficiency close to 90% throughout the charge sequence. A battery model representing the state-of-charge, charge and discharge dynamics is used for characterizing the battery as a load for the resonant converter.