Confused by all the new rechargeable technologies? An analysis of how batteries behave under repeated charging and discharging reveals the positives and negatives of nickel cadmium, nickel metal hydride and lithium ion systems so you can determine which is best for your application.

photoWhat causes a battery to wear down — is it mechanical or chemical? The answer is both. A battery is a perishable product that starts deteriorating right from the time it leaves the factory. Similar to a spring under tension, a battery seeks to revert back to its lowest state of energy. The speed of aging is subject to depth of discharge, environmental conditions, charge methods and maintenance procedures, or the lack thereof. Aging and user-conditions affect each battery chemistry differently.

As part of an ongoing research program to find the optimum battery system for wireless applications, Cadex performed life cycle tests on Nickel Cadmium (NiCd), Nickel Metal Hydride (NiMH) and Lithium Ion (Li-ion) batteries. All tests were carried out on Cadex C7000 series analyzers.

The batteries received an initial full-charge, and then underwent a regime of continued discharge/charge cycles. The internal resistance was measured with Cadex’s proprietary OhmTest method, and the self-discharge was obtained from time-to-time by reading the capacity loss incurred during a 48-hour rest period. The test program involved 53 batteries of different models and chemistries.

When conducting battery tests in a laboratory, it should be noted that the performance in a protected environment is commonly superior to those in field use. Elements of stress and inconsistency that are present in everyday use cannot always be simulated accurately in the lab.

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