The shape of the charge curves for battery voltage and the current supplied to the battery during charging is referred to as its charge algorithm. Not only do various battery chemistries differ in how they must be charged, but within a particular chemistry, the actual cell construction can require a unique charge algorithm. While it is beyond the scope of this catalog to explain the complex chemistry behind each charge algorithm, we will attempt to define the more basic algorithms employed at Patco, and illustrate their basic characteristics.

Lead Acid

Conventional parallel plate lead acid batteries need approximately 1/10 of their capacity in amp hours supplied as a constant current during the first eighty percent of the charge restoration process. Since the basic chemical reaction changes at that time, and additional gas is produced, the charge current needs to taper during the completion of the charging process, ending at 1/3 to 1/10 of the current supplied during the bulk charge phase. If a constant current source is used for the bulk charge phase, then a constant voltage source used during the second phase, the basic requirements will be met, and the resultant battery charge current curve approximates that shown in Figure 1.

Figure 1