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.