Over the past several years, there has been increasing pressure put on automobile manufactures to limit their vehicle's emissions. In fact, California has passed a measure requiring an increasing fraction of new vehicles to have zero emissions starting 1997. Many other states have been following their example. The only known way to have no emissions is with an electric powered vehicle. This paper describes how much research has been spent in determining the behavior of an electric powered vehicle's Pb-acid secondary battery when subjected to normal conditions through the use of an improved equivalent circuit model.