A three-dimensional thermal model has been developed to gain better understanding of thermal behavior of battery cells in a pack under simulated driving cycles. The numerical approach incorporates a three-dimensional CFD pack-level sub-model, a one-dimensional battery pack network sub-model, and a three-dimensional thermal and electrochemical coupled cell/module level sub-model so that the battery non-uniform heat generation rate, the battery temperature distribution as well as battery temperature variation across a pack can be quickly predicted. In particular, the flow profiles of each individual battery cooling channel are calculated using the three-dimensional CFD sub-model. Using the predicted flow profiles of the cooling channel as flow boundary conditions the thermal behavior of battery cells is predicted using the one-dimensional battery pack network sub-model and the cell/module level thermal sub-model, in which both electrochemical reaction and double layer effect of battery cells are considered. The thermal behavior of battery cells is correlated through physical tests. Finally, the effects of the cooling flow of battery pack and the design of battery pack cooling system on non-uniformity of individual battery cell temperature and battery cell temperature variation across the pack under simulated US06 driving cycles are studied and discussed. (C) 2012 Elsevier B.V. All rights reserved.