Onboard Unidirectional Automotive G2V Battery Charger Using Sine Charging and its Effect on Li-Ion Batteries

On-board battery chargers are used in electric and plug-in-hybrid electric vehicles (EV/PHEV) for charging the battery from the utility power grid. Various cost-effective topologies with reduced mass are now being proposed for the on-board charger to charge the Li-ion batteries used these vehicles. This paper proposes two unidirectional battery charger topologies with a novel single stage control that provide rectified sinusoidal charging currents to the battery, thus eliminating the need for the bulky dc bus electrolytic capacitor of conventional systems. The advantages of eliminating the electrolytic capacitors include reduced size, mass and cost of the charger and improved reliability. Simulations of the voltage and current waveforms during normal operation are presented. An accelerated cycle charge/discharge testing of the battery cells with low frequency current ripple was conducted to determine the impact of the low frequency 120 Hz ripple on the Li-ion battery capacity and life. The test results are encouraging and show negligible impact of sine charging on Li-ion battery performance.