HP HP-Bench-Briefs-1986-03-04 free download

File name HP-Bench-Briefs-1986-03-04.pdf

KFORMATION FROM HEWLETT-PACKARD March/April 1986 Battery Charging With a Hewlett-Packard - Power Supply Introduction Charge Methods The charging and discharging of One of the most common approaches batteries has become an area of to charging batteries is the "constant careful study in the aerospace and current" method sometimes referred automotive industries as well as to as a "slow charge." As the name many others. Precise control of both implies, it typically requires 14-16 the charging and discharging char- hours to fully charge a nickel- acteristics of batteries may be nec- cadmium cell. The charge rate for essary in applications ranging from this method is typically O.lC, where satellite design to battery develop- C is the nominal ampere-hour rating Figure 1. Constant Current Charging ment and evaluation. of the cell. At this charge rate standard Ni-Cad sealed cells can battery to the power supply and Although sufficient for many con- tolerate an overcharge for extended setting the proper charging rate, the sumer applications, the comparatively periods of time without damage or charging operation can be left poor charging control of readily avail- serious performance degradation. unattended. able battery chargers may not provide the precision necessary in many crit- The other charging method we will Constant Current Charging ical applications. To achieve a high discuss is the "taper charge" method. Procedure degree of accuracy, stability and When charging lead-acid cells, many regulation, the dc power supply ap- manufacturers recommend that the The procedure for setting the charging proach can be utilized. This same charging current be reduced as the rate and full charge voltage on con- power supply, with little or no mod- charge nears completion. This "taper stant voltagelconstant current power ification, can also be used for con- charge" can be accomplished by in- supplies is as follows: trolled battery discharging. serting a small resistance in series with one of the load leads between 1. Turn both the VOLTAGE and Two different types of battery charg- the power supply and the battery CURRENT controls fully coun- ing techniques using Hewlett-Packard being charged. terclockwise (CCW). dc power supplies will be explained in this article. For information on Constant Current Charging 2. Pla