Design of a Battery Management System based on matrix switching network

Abstract

Battery Management Systems are the key modules for Lithium-Polymer (LiPo) batteries. They control the charging /discharging parameters, measure the voltages and state of charge (SOC) of the battery cells, equalize the charge/discharge characterizes of individual battery cells and notify the main controller of the status of the battery pack. They are also the critical safeguards against potential damages to the batteries. Due to the fact that LiPo batteries have great energy density, low discharge rate, high cell voltage and lack of memory effect, they are widely used in applications such as electric vehicles and electric bicycles. However, because one battery pack needs a lot of battery cells connected in series, the battery pack is prone to fail than a single cell battery. Moreover, the battery cells are always different in the SOC and internal impedance. This means if the weak cell hits the protection limit while the other cells in the series are still sufficient to power the system, the battery pack cannot be used either. This will limit the capacity and efficiency of the battery pack. To improve the reliability and capacity of Li-Po battery pack, this paper propose a novel battery management system, on which, individual battery cell can be dynamically connected to or disconnect from any position of the battery series via the matrix switching network. By appropriately controlling the matrixswitching network, the battery cells can be configured to different configurations to suit different application scenarios e.g. active cell balancing, multi-voltage output, and weak/fail cell replacement.