The positive plates with conductive materials, Pb3O4 and BaPbO3, in automotive lead-acid batteries were investigated by measuring their current and potential distributions in the course of formation and discharge. It is found that these two conductive materials, especially Pb3O4, enhance the formation in the initial stage greatly and that they make the current and potential distributions more uniform. In the discharge, the addition of Pb3O4 increases the capacity of the positive plate, but it is unfavorable to the paste curing and causes poor contact between active mass (AM) particles so that the polarization increases greatly at 3C discharge rate. The BaPbO3 additive improves not only the formation but also the discharge performance because of its stability in acidic media and at high polarization. The violent charge at high polarization around the plates in the initial formation can lead to poor AM contact and high polarization resistance.