Floating Capacitor Active Charge Balancing for PHEV Applications
Creators:Chuang, Ying Chieh
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Publisher:The Ohio State University
Series/Report no.:The Ohio State University. Department of Electrical and Computer Engineering Honors Theses; 2010
Li-ion battery chemistry provides high energy density, which is extremely important for plug-in hybrid vehicles (PHEV). However, Li-ion batteries are also more prone to damage by overcharging and over-discharging. For PHEV applications, a battery pack consists of many battery cells in series and parallel configurations. Over time, the state of charge (SOC) of individual cells can deviate from one another because of various conditions and manufacturing variability, increasing the likelihood of over- charging and/or over-discharging individual cells. This project explores the use of a floating capacitor active charge balancing (ACB) system for a Li-ion battery pack. A prototype floating capacitor ACB system is built and implemented in a custom built pack consisting three parallel strings with four cells in each string (3P4S). The battery pack is exercised on a cycler to deviate the SOCs of the cells, and the ACB system is used for no-load balancing. Results verify previous simulations of the same system. The floating capacitor ACB system sufficiently balances the pack with no load balancing. In addition, the system is made of simple components, decreasing complexity and provides good economic efficiency.