Distributions of current density and potential on the automotive negative plate during its formation and discharge processes have been studied by an in situ electrochemical scan technique. It is found that the current and potential distributions are uneven at the beginning of the formation. However, these distributions are much more uniform than those of the positive plate and the resistance is much smaller because of the lead skeleton formed on the negative plate. At the end of the formation the distributions are relatively uniform, and the current density in the upper part of the plate is a little higher than that in the lower part. The resistance and the polarization increase obviously at the bottom and on the top of the negative plate. During its discharge, the polarization is also high and the utilization of the negative active mass becomes low in these regions. Therefore, the formation of the negative plate greatly affects the current and potential distributions and the battery performance in its discharge.