Analytical study on low-frequency ripple effect of battery charging

With the recent interest in environment-friendly vehicles such as electric vehicles (EVs) and plug-in hybrid electric vehicles (PHEVs), various topologies are being proposed for the on-board charger (OBC) required to charge the lithium battery that serves as the energy storage system. If a specific topology is selected and used, the output current of the charger is bound to contain low-frequency ripple that is twice the input power supply frequency. In this study, to analyze the effects of the low-frequency ripple on the lithium battery, a number of charging/discharging cycles are performed to apply low-frequency ripple current and constant current to PHEV lithium battery cells with similar properties. In addition, we conducted capacity test for each specific cycle to compare their performances to analyze the effects of OBC's low-frequency ripple on the battery.