A Microcontroller-based fast charger with state-of-charge estimation for LiCoO2 battery

In this paper, a microcontroller-based charger of the LiCoO₂ battery module is realized. The main structure of the proposed system is the power factor corrector with a full-bridge phase-shift converter, the charging strategy is varied according to the battery module´s state of charge (SOC). Furthermore, we directly capture the related data of the battery cells from the battery management system via the I²C interface, and then through the open-circuit voltage method integrating the coulomb integral method to find the lowest state of charge of the battery cell as a benchmark charge to adjust charging strategy. The pre-charge current is used when the SOC of the battery is lower than 15%. And then we employ the constant current charging if the SOC is from 15% to 75%. Finally, the charging strategy of the last phase will change to constant voltage charging to avoid the over-charging phenomenon.