Today, it is possible to design a mathematical model of lead-acid battery on a laptop from scratch with MATLAB. It still takes time to develop, but nowadays these models alone cannot be considered innovations anymore because anybody is able to do the same with the appropriate tools. More than ever, the actual innovation lies in the answer given to the most important question: a model to do what? Here, the model's main goal is to simulate the flooded battery behavior in all vehicle life cycles. Thus, it seems legitimate to validate them under different operating conditions with experimental data to prove that the simulation results are reliable. It is challenging but feasible, notably by making a correct selection of the parameter value ranges and studying how they influence the output. Another goal is to understand the battery behavior changes due to the physicochemical processes involved at various rates and temperatures to explain Peukert's law and the impact of temperature on vehicle cranking. The final objective of this model is to find parameter changes corresponding to the main aging phenomena to simulate new and also used batteries. (C) 2009 The Electrochemical Society. [DOI: 10.1149/1.3224868] All rights reserved.