This work employs a one-dimensional and a two-dimensional model to predict the thermal behaviour of 30-A h hTi/MH batteries. The temperature of battery can rise to about 45 degrees C during 15-A charging under natural convection. Batteries. attached with aluminum fins exhibit an effective heat-dissipation behaviour under either natural convection or forced convection conditions. The temperature is around 37 and 32 degrees C under natural convection and forced convection, respectively. During discharge, the temperature rise of the battery is only about 6 degrees C under adiabatic conditions. In a closely-packed module, natural and forced convection is unable to reduce the temperature increase in the central part of a module. Experimental results indicate that the one-dimensional model is sufficient for the system operating under natural convection condition. For forced convection, the prediction is more accurate with the two-dimensional model. In general, the simulation results correlate well with measurements.