Endurance of batteries and separators in automotive applications under high-temperature conditions

Endurance tests under high-temperature conditions have been performed on three groups of automotive batteries. One group has been assembled with polyethylene pocket separators for the negative plates, another with polyethylene pocket separators with glass mats for the positive plates, and a third with leaf-type synthetic pulp separators with glass mats. Negative plates developed a sand-like appearance in the batteries assembled with the polyethylene pocket separators for the negative plates. Evidence of piercing shorts is found in batteries assembled with polyethylene pocket separators with glass mats for the positive plates. Also presented are the results of a structural analysis of failures in polyethylene separators after a series of cycle-life tests under high-temperature conditions, together with a theoretical examination of the deterioration process of the polyethylene pocket separators. It is concluded that battery assembly with polyethylene pocket separators with glass mat is an effective way to achieving good endurance (i.e., life extension at high temperature). On the other hand, the selection of leaf-type synthetic pulp separators with glass mats is the best approach for hot climatic conditions.