Search Results

Deep charge and discharge cycling of 24 Volt battery strings composed of two 12 Volt VRLA batteries wired in series affects reliability and life expectancy. This is a matter of interest in vehicle power source applications. These cycles include those specific operational cases requiring the delivery of the full storage capacity during discharge. The concern here is related to applications where batteries serve as a primary power source and the energy content is an issue. It is a common practice for deep cycling a 24 volt battery string to simply add the specified limit voltages during charge and discharge for the individual 12 Volt batteries. In reality, the 12 Volt batteries have an inherent capacity variability and are not identical in their performance characteristics. The actual voltages of the individual 12 Volt batteries are not identical.

The US Army has recently transitioned to using “maintenance free” batteries in its ground vehicles to increase the over-all vehicle readiness. Using lead-calcium alloy grids in place of the “reduced maintenance” design decreases water loss. This loss of water is known to be a measure of the battery self discharge. In this study, the charging of SLI batteries was examined over a range of operating temperatures as a means for characterizing the self-discharge rate as a function of battery voltage and temperature. The battery response was modeled analytically. Current activities are directed toward achieving a better description of the battery self-discharge over extreme environmental conditions.