A simple mathematical model is presented and used to analyze the potential and current distributions in a HORIZON® sealed lead‐acid battery. It was found that an increase in the thickness of an electrode would not enhance the discharge rate of that electrode; instead, it causes the transfer current distribution to be less uniform in the electrode. Also, the ohmic drop across the separator would decrease with a decrease in the thickness of the separator more rapidly when the thickness is small than when it is large. In addition, it was found that efficient high‐capacity, high‐rate electrodes must consider the electrode reaction kinetics because of the high sensitivity of transfer current distribution to the reaction kinetics.