Charge Equalization on Series-Connected Battery Modules by Digital Controller

This research aims at the realization of charge equalization on series-connected battery modules by digital controller. A charge equalization system on high-voltage high-capacity series-connected lithium-iron batteries is developed. The system includes hardware, firmware, equalization strategy and protection peripherals. For the hardware, a capacitor is adopted as the intermediate for the charge transference between higher and lower charged modules. The charge transference between battery modules and capacitor is performed via bidirectional flyback converters. For the firmware, LPC122x series of 32-bit microcontrollers are used as the digital controllers, and a battery management IC is used to sense the battery information. The controller area network (CAN) bus provides the communication network for the modules in the system. The proposed battery modules with fast equalization can be achieved by executing the balancing strategy and protection circuits. Experimental results show that the charge equalization system could achieve module to module charge equalization between 22 battery modules accurately, making the voltage difference be less than 100 mV after equalization.