A generic three‐dimensional thermal model was developed for analyzing the thermal behavior of electric vehicle batteries. The model calculates temperature distribution and excursion of a battery during discharge, charge, and open circuit. The model takes into account the effects of heat generation, internal conduction and convection, and external heat dissipation on the temperature distribution in a battery. The three‐dimensional feature of the model permits incorporation of various asymmetric boundary conditions; thus, the effects of cell orientation and packaging on thermal behavior can be analyzed for a multiple‐cell battery pack. Various modes of boundary heat transfer such as radiation, insulation, and natural and forced convections were also included in the model. Model predictions agreed well with the temperature distributions measured in nickel/iron batteries. Application of the thermal model to a closely packed 330 Ah module of five cells indicated that excessive temperature rise will occur upon discharge. Forced air convection is not effective for cooling the module.

Mathematical analysis has been carried out for the heat transfer in lead‐acid batteries designed for use in electric vehicles. This analysis has shown that the heat generated in the battery during recharge cycles may cause a noticeable rise of battery temperature in the absence of proper thermal management. The results have shown that the ratio of the temperature rise during charge is closely related to the ratio of the energy densities of the two batteries. Of the cooling methods examined, electrolyte circulation along the battery plates was found to be the most effective in removing heat and providing a uniform temperature field. Numerical solutions are provided for the engineering evaluation of heat‐removal design during battery cycling processes.

Modeling studies have been conducted to determine the temperature field in a lead-acid cell contemplated for load-leveling applications, with daily duty cycles and a weakly equalization charge. The results show that under the proposed daily cycling and without a forced cooling, a maximum temperature rise of 16~ can be expected at the center of a proposed 9.76 kW-hr cell (48.26 cm length X 45.72 cm width X 127 cm height). For such tall lead-acid cells, reduction of cell length by about one-half would reduce the temperature rise by 7~176 without employing forced cooling. Conventional water cooling at the cell termirmls has little effect in lowering the cell maximum temperature. Moreover, cooling may induce a large temperature gradient in the vertical direction of the cell, which may cause a nonuniform current distribution over the electrode leading to a gradual loss of cell capacity and cycle life. Practical cells in use often incorporate "air lift pump" that facilitates electrolyte stirring or an electrolyte circulation design to minimize the extreme temperature gradients. Gassing during the weekly equalization charge of loading-leveling cells may also enhance internal heat transfer, causing a more uniform temperature distribution. After the weekly equalization charge, the cell temperatures resume their initial values at the end of the rest period.Thermal behavior in lead-acid batteries during cycling is an important factor affecting battery performance and cycle life. Temperature effects become even more critical for the advanced batteries employed in electrical vehicle propulsion and utility load-leveling applications. Poor battery design can result in significant temperature rise and temperature gradient in the battery during charge and discharge cycles. This temperature rise may cause enough variation in the physical and chemical properties of the battery components to lead to a gradual loss of cell capacity and cycle life. Baker, Gidaspow, and Wasan (1) have given a review for the thermal phenomena in fuel cells and batteries as well as the mathematical treatment to obtain the analytical solution for the temperature fields in fuel cells and batteries. They derived general solutions for maximum cell temperatures at steady state with a boundary condition of constant cell wall temperature. A similar approach has also been. applied for the calculation of the maximum temperature in silver-zinc batteries at steady state and at isothermal wall conditions by Meredith and Uchiyama (2). The present work employs finite difference method to study transient thermal phenomena in loadleveling lead-acid cells under conditions of variable cell wall temperature. The same method was applied by .us recently to a study of a transient thermal phenomena in lead-acid cells which were designed for electric vehicle propulsion (3). That study (3) addressed heat transfer behavior across the electrode, the electrolyte and their interface for a PbO2 electrode; the temperature field in~ a composite lead-acid battery; and the proposed batte...

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