Numerical simulation on fast charging nickel metal hydride traction batteries

Computer simulation of battery performance, especially from first principles, can provide valuable information for understanding how a battery performs under dynamic conditions. This paper describes recent progress made in incorporating both oxygen and hydrogen recombinant cycles in a computational fluid dynamics based numerical model to simulate nickel metal hydride (Ni-MH) traction battery performance. It is important to show that the incorporation of the hydrogen recombinant cycle is useful and how that affects simulation results in predicting and validating, for example, fast charging of an 85 Ah Ni-MH battery system made of AB(2)-hydride based cells. From our previous studies, we have found that in cells of such a battery, the hydrogen recombinant cycle is critically related to cell performance, particularly in fast charging behavior at 1-3C rates. Using the experimental data collected in our laboratory, we validated the model and showed comparisons between results from predictions made with and without the hydrogen recombinant cycle. Implications of the simulation results in the understanding of the limiting mechanism in the fast charging conditions are also discussed. (C) 2004 The Electrochemical Society.