Theory of Battery

http://en.wikipedia.org/wiki/Battery_%28electricity%29

http://electronics.howstuffworks.com/battery.htm

In the battery, the positive and negative polarities are relative concepts. In deed, in battery system one of the two poles is for example negative and the other is more negative in comparison with the electrolyte material.

In fact, in a separated battery bank after electrochemical stability, the charge transmissions between electrolyte media and both of two electrodes will be stopped and opposite transmission current will be impossible.

A similar mechanical phenomenon is heat transmission between two metal rods with different thermal conductivity coefficiency that are connected to a very hot metal plate. The thermal difference at the end of rods can cause the heat transfer through a metal wire between them, but the heat transmission between two rod is impossible through the hot metal plate because the plate is warmer than both of them.