CHARGE EQUALIZATION FOR SERIES CONNECTED BATTERY STRINGS

A simple technique that provides charge equalization for a series stri ng of battery cells is presented, The advantages of accurate charge eq ualization are very substantial and include reduced damage to battery cells in the stack, and a dramatic increase in battery life, The basic technique utilizes a simple isolated dc/dc converter with a capacitiv e output filter along with a multi-winding coaxial winding transformer (CWT). The coaxial winding transformer is known for its Iom and contr olled leakage inductance, The transformer leakage inductance is used a s the main driving impedance to control the total charging current for the individual cells, The use of one low-power converter to obtain ch arge equalization for the entire battery string is very attractive and leads to a low cost implementation.