Study of high-capacity single-body Li-ion battery charging and discharging system

This paper proposed a high-efficiency battery charging and discharging system for high-capacity single-body Li-ion battery. This system can work as battery formation system or battery test system. The main system structure includes a single-phase bi-directional PWM rectifier, dc-link, half-bridge converter with current-doubler synchronous rectifier as charging unit and interleaved pull-push converter as discharging unit, and control unit and communication port. The charging and discharging units were designed separately for more feasible control strategy, because several such units can be paralleled to be a bigger system through dc-link. The energy balance among batteries and the grid is controlled automatically. There are three system operation modes: all batteries charging from the grid or discharging to the grid, energy transfer among charging batteries, discharging batteries and the grid. Besides of basic functions, battery energy records were accomplished by communication with the host computer. Such records will beneficial to the battery lifetime evaluation.