Explore what causes corrosion, shedding, electrical short, sulfation, dry-out, acid stratification and surface charge
A lead acid battery goes through three life phases, called formatting, peak and decline (Figure 1). In the formatting phase, the plates are in a sponge-like condition that is being exposed to a liquid. Exercising the plates allows the absorption of liquid much like squeezing and releasing a hardened sponge. As the nooks and crannies fill, the capacity gradually increases.
Formatting is most important for deep-cycle batteries. They require 20 to 50 full cycles to reach peak capacity and field usage achieves this. When breaking in a battery, manufacturers recommend going easy. Starter batteries are less critical and do not need priming; the full cranking power is available from the beginning, although the CCA reading will go up slightly with early use.
Figure 1: Cycle life of a battery
The three phases of a battery are formatting, peak and decline.
Courtesy of Cadex
A deep-cycle battery delivers 100–200 cycles before it starts the gradual decline. Replacement should occur when the capacity drops to 70 or 80 percent. Some applications allow lower capacity thresholds but the time for retirement should not fall below 50 percent as aging may hasten once past prime. Apply a fully saturated charge lasting 14 to 16 hours. If this is not possible with each charge, allow the battery to fully saturate once every few weeks. Operate at moderate temperatures and if at all possible, avoid deep discharges; charge more often.
The primary reason for the relatively short cycle life of a lead acid battery is depletion of the active material. According to the 2010 BCI Failure Modes Study,* plate/grid-related breakdown has increased from 30 percent five years ago to 39 percent. The report does not give reasons for the increased wear-and-tear, other than to assume that higher demands of starter batteries in modern cars induce added stress.
While the depletion of the active material is well understood and can be calculated, a lead acid battery suffers from other infirmities long before plate- and grid-deterioration sound the death knell. These conditions include Corrosion / Shedding, Short, Sulfation, Water Loss / Dry-out, Acid Stratification and Surface Charge.
* Every five years, the Battery Council International Technical Subcommittee conducts a study to determine the failure modes of batteries that have been removed from service.
Last Updated 2015-04-22
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