On temperature compensation for lead acid batteries in float service: its impact on performance and life

Manufacturers of lead acid batteries usually publish temperature compensation factors that apply to the operating float voltage in standby service, which is intended for use within the range of recommended operating temperature. They are applied to adjust the float voltage and maintain the battery in a full state of charge. For flooded (i.e., vented) lead acid batteries, however, temperature compensation is rarely used in practice. This paper discusses some of the basic principles of temperature compensation and where they could be beneficially employed in standby float service. It starts with presenting data for flooded cells and computes effect of temperature on (a) voltage and (b) current. It then goes on to illustrate the genesis of the factors that exist for these cell types. Data for VRLA cells are then reviewed, to show how they differ from the flooded cells with respect to the applicable compensation factor. For flooded cells, when a narrow range of temperature change is encountered, it is seen that temperature compensation is not necessary. Since float current increases twice as fast for VRLA cells when compared to the flooded cells, the urgency for compensation is real. These discussions should clarify the objective in picking the temperature compensation factor for VRLA cells, which is to prevent thermal runaway while keeping the battery in continuous operation