Design and implementation of Li-ion battery charger using state-of-charge estimation with fuzzy temperature control

In this paper, a novel lithium-ion (Li-ion) battery charger is proposed; the proposed charger first takes the state of charge (SOC) information into account and adjusts the charging current accordingly. In order to further improve the charging efficiency, a fuzzy-logic-control-based (FLC-based) technique is also employed. The proposed FLC takes the temperature rise and the gradient of temperature rise of battery into account, and fine-tune the charging current accordingly. In this paper, the power stage is implemented using the synchronous-rectified buck converter. The digital compensator, digital filter and the SOC adaptive algorithm is implemented using the dsPIC digital signal controller from Microchip Corp; while the fuzzy logic controller is realized using the LabVIEW on a personal computer. In addition to the hardware, a graphical user interface is also presented. According to the experimental results, the charging efficiency of the proposed system can be increased and the performance of the proposed charger can be improved. Comparing to conventional constant-current constant-voltage (CC-CV) method, the proposed charging technique can reduce the average temperature rise for 23.2% while maintaining similar charging time.