A　cell　with　tall　plates　was　simulated　by　two　cells　and　the　controlled　voltage　with　time　was　successfully　used　to　measure　the　response　current-time　curves.　It　indicates　that　the　current　in　the　upper　part　of　the　plate　is　much　higher　than　that　in　the　lower　part　in　early　stage　of　the　discharge,　but　in　late　stage,　it　is　reversed,　especially　at　high　discharge　rates.　The　upper　part　of　the　plate　has　higher　capacity　and　deeper　depth　of　discharge　(DOD)　so　that　the　active　mass　degrades　and　sheds　more　quickly　in　cyclic　applications.　In　the　initial　discharge,　the　lead　sulfate　formed　at　positive　plates　produces　the　internal　stress　and　enhances　the　electric　connection　among　the　active　mass　particles.　But　the　positive　active　mass　only　contributes　a　little　to　the　conductivity　of　plates.　The　negative　active　mass　with　a　bit　shrinking　but　no　passivation　has　better　conductivity　than　the　expanded　active　mass.　The　higher　ohmic　polarization　of　the　active　mass　appears　at　higher　discharge　rates,　in　the　upper　part　of　the　plates,　in　the　late　stage　of　the　discharge,　in　aged　battery,　especially　for　negative　plates.　©　2012　Elsevier　B.V.　All　rights　reserved.