AN227| Application Note
Maxim/Dallas > App Notes > BATTERY MANAGEMENT Keywords: pulse charger, linear charger, charge efficiency, DS2770, charge controller, battery, cell aging, Li+, Li-Ion, CC/CV charger, charger, chargers, lithium ion
Dec 10, 2002
APPLICATION NOTE 227
Charge Efficiency and Cell Aging Effects of the DS2770 Li+ Pulse Charger vs. Linear Chargers
Charging a battery cell can be accomplished using a variety of methods including linear (CC/CV) charging and pulse charging. This application note compares these charge methods with respect to the effect each has on charge efficiency and cell aging. An experiment to study the effect of pulse charging and linear charging on both charge efficiency and cell aging is described. Results are presented that show that the pulse charging method charges battery cells faster and ages the battery cell less than the linear charge method.
Introduction
Pulse-charging topology shares many of the same desirable advantages as linear charging including simplicity, low cost, small size, and few external components. It offers a benefit over linear chargers in that heat is dissipated in the wall adapter instead of the charger itself. However, perceived disadvantages exist which put forth the notion that the pulse charging of a Li+ cell prematurely ages the cell, resulting from subjecting it to the same current during the constant current region and the pulsed region, where it is very near its maximum voltage. However, data taken does not support this theory. A comparison between a linear (CC/CV) charger and the DS2770 Battery Monitor and Pulse Charger will be presented, focusing on the effect of each with respect to charge time, charge capacity, and cell aging.
Charge Time and Cell Aging Experiment
The DS2770 Battery Monitor and Charge Controller, which features a Li+ pulse charger, was used to provide the pulse charge profile and to serve as the coulomb counter for the experiment. The coulomb count was used as a measurement of diminishing capacity as the cell was cycled. Figure 1 illustrates the test setup used for the experiment.
Figure 1. Test setup for linear and pulse charger experiment.
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