An electronic equalizer for series connected batteries

A ramp type of battery equalizer circuit for series connected batteries has been developed. The analytical model for this circuit is based on a simplified multi-winding transformer model and a nonlinear diode model. It predicts the circuit performance and has been verified experimentally. The linearized model offers qualitative results describing the effect of each circuit parameter and gives a general design guide for the circuit design. The non-linear equalizer model provides a convenient approach for the frequency response analysis of the current sensitivity and the optimum switching frequency selection.; A proposed arrangement of the transformer secondary windings reduces the number of the secondary windings by 50% and simplifies the transformer construction significantly. A transformer with a spoke type of a winding arrangement has been constructed to achieve low and uniform secondary leakage inductances. Extra capacitors paralleled with the drain-source of the FETs further reduces the switching loss.; Both steady state and dynamic charge equalization experiments were conducted and compared for different switching frequencies and power. These experimental results verify the validity of the model and the theoretical results, and they also demonstrate the effectiveness of the proposed electronic equalizer.