Implementation of charger and battery management system for fast charging technique of Li-FePO4 battery in electric bicycles

摘要

This paper presents a fast charging scheme for a Li-FePO4 battery pack used in electric bicycles. In general, a BMS of a battery pack in electric bicycles has no communication with chargers. In such system, the battery pack is charged without taking the voltage of individual cells into account and such system works well when charging with normal charging current level. In contrast, for fast charging, one cell may suffer overvoltage rapidly during charging with high current. This can lead to shortened life-time or sudden damage of the battery. In order to avoid the mentioned problem, the charging process is executed using measured data from the BMS. The developed charger adjusts the charging current to the maximum possible limit corresponding to the voltage of the cell which has the highest voltage in the pack, so that no individual cell suffers overvoltage during charging. The proposed scheme was implemented and tested. The hardware prototype and the experimental results validate the functionality of the proposed scheme.