Analytical assessment of the thermal behavior of nickel-metal hydride batteries

Introduction A three-dimensional analytical thermal model [1] is adapted to describe thermal response of Nickel-metal hydride (NiMH) batteries to heat generation during their operation. The model is based on integral-transform technique [2] that gives a closed-form solution for the fundamental problem of unsteady heat conduction in batteries with orthotropic thermal conductivities, where the heat generation is due to irreversible (polarization) and reversible (entropy change) losses. The full-field solutions take the form of a rapidly converging triple infinite sum whose leading terms provide a very simple and accurate approximation of the battery thermal behavior with modest numerical effort. The accuracy of the proposed model is tested through comparison with numerical and experimental data [3,4]. The method is used to describe spatial and temporal temperature evolution in a sample prismatic NiMH battery (30 A h, NEXcell battery, USA) [cf. Fig. 1] during fast charge processes while subjected to convective cooling at its external surfaces. The obtained results show that this theoretical model can be used as a fast yet accurate tool for the design of battery thermal management systems.