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Need the battery the weak link?

By Isidor Buchmann, Cadex Electronics Inc.

isidor.buchmann@cadex.com

July 2003

When charging a battery, the ‘ready’ light will eventually illuminate, indicating that the battery is fully charged. The user assumes the battery has reached its full potential and takes the pack with confidence.

Figure 1: The green ‘ready’ light on a charger does not provide performance verification. It simply reveals that the battery is fully charged.

The ‘green light’ does not guarantee a good battery; neither does it assure sufficient runtime. “Ready” only indicates that the battery is fully charged on whatever space that was available to fill. In fact, weak batteries charge more quickly (because there is less to fill) and remain on ‘ready’ longer than strong packs. Bad batteries tend to gravitate to the top and become a target for the unsuspecting user. Batteries that go “ready” first may be deadwood.

A weak battery can be compared to the fuel tank of a car that has been filled with rocks. Refueling is quick because the tank holds little fuel. The fuel gauge on the dashboard shows FULL and everything appears normal except for the distance traveled.

The rechargeable battery is a corrosive device that gradually loses the ability to hold charge. In the first year, a battery-operated system works well because the batteries are fresh. During the second year, some batteries start losing capacity and the reliability begins to decline. New packs are added, and in time the battery fleet becomes a jumble of good and failing batteries. That’s when the battery headaches begin. Figure 2 illustrates an aged battery with the so-called rock content.

Figure 2: A battery pack can be divided into three imaginary sections: (1) the empty zone that can be refilled, (2) the available energy, and (3) the rock content that no longer holds charge.

How are the batteries checked? The answer is battery maintenance, commonly done with a battery analyzer. While organizations such as public safety have been using battery analyzers for many years to restore and prolong nickel-based batteries for two-way radios, analyzers are now making their way into servicing batteries for laptops, handheld scanners, medical and other industrial devices.

Fleet batteries should be serviced once every two months. Attaching a small battery label containing service date, due date and capacity reading keeps track of the serviced batteries. This system is self-governing because the user only picks a battery that has properly been serviced and labeled.

As part of the maintenance program, expired batteries are segregated and serviced on a battery analyzer. Packs that regain full capacity are relabeled and returned to the field; those that fall below the set target capacity are replaced with new packs. Modern battery analyzers enable non-technical staff to service a battery fleet in less than 30 minutes per day.



Figure 3 illustrates a printer with a sample label. The printer connects directly to the battery analyzer or to a PC if interfacing software is used.

The question is often asked: “Does battery maintenance prolong battery life?” The answer is yes. The life of nickel-based batteries can typically be doubled with scheduled service. On lithium-ion, the purpose of battery maintenance leans towards verifying performance rather than restoring weak packs and extending life. This reduces unexpected downtime caused by aging batteries. Lithium-ion batteries provide a service life of two to three years and deteriorate even when not in use. Cool temperature reverses the aging process.

Summary

Charging alone does not assure reliable batteries. Some quality control is required to keep a battery fleet healthy. Not only does battery maintenance prolong the life of nickel-based batteries, maintenance weeds out unwanted deadwood. Such deadwood can be identified relatively easily because batteries do not die suddenly but gradually get weaker over time.

Problems with weak batteries are most apparent in emergencies and in heavy traffic when full performance is needed. Battery failure during such critical moments is not an option. To strengthen the battery fleet, organizations are beginning to take a proactive approach in terms of battery maintenance and record keeping. The cost savings are apparent. Longer battery life and fewer units needing repair are the direct result. The website www.cadex.com provides additional information on battery needs and service equipment.

About the Author

Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world.


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