The 'Green Light' Lies

Isidor Buchmann
Cadex Electronics Inc.
isidor.buchmann@cadex.com
www.buchmann.ca

April 2001

When charging a battery, the ready light will eventually illuminate, indicating that the battery is fully charged. The user assumes that the battery has reached its full potential and the battery is taken in confidence.

In no way does the ‘green light’ guarantee sufficient battery capacity or assure good state-of-health (SoH). Similar to a toaster that pops up the bread when brown (or black), the charger fills the battery with energy and ‘pops’ it to ready when full (or warm).

The rechargeable battery is a corrosive device that gradually loses ability to hold a charge. Many users in an organization are unaware that their fleet batteries barely last a day with minimal energy reserve to spare. In fact, weak batteries can hide comfortably because little demand is placed on them in a routine day. The situation changes when full performance is required during an emergency. Total collapse of portable systems is common and such breakdowns are frequently related to poor battery performance. Figure 1 shows five batteries in various states of degradation.

Figure 1:  Progressive loss of charge acceptance.
The rechargeable battery gradually loses its ability to hold charge.

Carrying larger packs or switching to higher energy-dense chemistries does not improve system reliability if the weak batteries are not ‘weeded’ out. Likewise, the benefit of using ultra-advanced battery systems offers little advantage if packs are allowed to remain in the fleet once their performance has dropped below an acceptable performance level.

Figure 2 illustrates four batteries with different ratings and state-of-charge (SoH) conditions. Batteries ‘B’, ‘C’ and ‘D’ show reduced performance because of memory problems and other deficiencies. The worst pack is Battery ‘D’. Because of its low charge acceptance, this battery might switch to ready after only 14 minutes of charge (assumed time). Ironically, this battery is a likely candidate to be picked when a fresh pack is required in a hurry. Because of low charge acceptance, it will last only for a brief moment. Battery ‘A’, on the other hand, has the highest capacity and takes the longest to charge. Because the ready light is not yet lit, this battery is least likely picked.

Figure 2:  Comparison of charge and discharge times.
Carrying larger batteries or switching to high energy-dense chemistries does not improve system reliability if weak batteries are allowed to remain in the battery fleet.

The weak batteries are charged quicker and remain on ‘ready’ longer than the strong ones. The bad batteries tend to gravitate to the top. They become a target for the unsuspecting user. In an emergency situation that demands quick charge action, the batteries that show ready may simply be those that are deadwood.

A weak battery can be compared to a fuel tank with a large indentation. Refueling this tank is quick because it holds less fuel. Like the ‘green light’ on a charger, the fuel gauge in the vehicle will show full when filled to the brim, but the distance traveled before refueling will be short.

Battery maintenance, a function of Quality Control

The reliability of portable equipment relies almost entirely on the performance of the battery. A dependable battery fleet can only be assured if batteries are maintained on a periodic basis.

Battery maintenance also needs proper documentation. One simple method is attaching a color dot, each color indicating the month of service. A different color dot is applied when the battery is re-serviced the following month. A numbering system indicating the month of service also works well.

A better system is attaching a small battery label containing service date and capacity. Like the pending service on a car, the label shows the user when maintenance is due. For critical missions, the user will pick a battery with the highest capacity and the most recent service date.

Battery analyzers are available that print a label revealing the organization, group, service date, expiry date (time to service the battery), battery capacity and ID number. The label is generated automatically when the battery is removed from the analyzer. Figure 3 illustrates such a label.

The battery labeling system is simple to manage. It is self-governing in the sense that the users would only pick a battery that is properly labeled and has recently been serviced. The system does not permit batteries to fall though the cracks and be forgotten. It is in the interest of the user to ensure continued reliability by including all batteries with dated labels for service.

Battery Maintenance Made Simple

Several methods are available to maintain a fleet of batteries. A simple, self-governing system is illustrated in Figure 4 to 6. Only 30 minutes per day should be required for a technician to maintain a large system. One or several battery analyzers are needed that are capable of producing battery labels. The recondition function is beneficial because it can restore batteries that otherwise would be discarded.

Figure 4:  Sorting batteries for servicing.
Each time a battery is taken from the charger, the user checks the service date on the label attached to the battery. If the date has expired, the battery is placed in a box marked ‘To be serviced’.

 
Figure 5: Servicing expired batteries
Batteries with expired dates are exercised; those that do not recover to the preset target capacity are reconditioned. Batteries that pass are re-certified by attaching a new label with dates and capacity reading.

Figure 6:  Returning batteries to circulation.
After servicing, the restored batteries are returned to the charger; those that failed are replaced with new ones. Battery maintenance assures that all packs perform at the expected capacity level.

When taking a battery from the charger, the user checks the service date on the battery label. If expired, the battery is placed into the box marked: ‘To be serviced’. Periodically, the box is removed and the batteries are serviced and re-certified with a battery analyzer.

After service, the batteries are re-labeled and returned to the charger. Those batteries that fail to meet the target capacity are replaced with new packs. All batteries in the charger are now certified to meet a required performance standard.

Battery maintenance has been simplified with the introduction of battery analyzers that offer a target capacity selection. All batteries must meet a user-defined performance test or target capacity to pass. Nickel-based batteries that fall short of the required capacity are automatically restored with the analyzer’s recondition cycle. Those packs that fail to recover are subsequently replaced with new packs.

Whether the batteries are serviced in-house with their own battery analyzers or sent to an independent firm specializing in that service, sufficient spare batteries are required to replace those packs that have been temporarily removed. When the service is done on location and the batteries can be reinstated within 24 hours, only five spares in a fleet of 100 batteries are required. This calculation is based on servicing five batteries per day in a 20 workday month, which equals100 batteries per month. If the batteries are sent away, five spares are needed for each day the batteries are away. If 100 batteries are absent for one week, for example, 35 spare batteries are needed.

Recondition is only effective for nickel-based batteries. It is worth noting that batteries with high self-discharge and/or shorted cells cannot be corrected with recondition; neither can a battery be restored that is worn out or has been damaged through abuse.

A group of batteries that cannot be deep discharged by recondition are ‘smart’ batteries. These are packs that contains a microchip that is kept alive with the battery’s own energy. Discharging these batteries below a certain voltage point will put the battery to sleep and vital information may be lost. A recharge often fails to wake up the microchip and the battery appears dead.

Choosing a Battery Maintenance System

For a large battery fleet, a battery analyzer should be capable of interfacing with a PC. Batteryshop™ by Cadex Electronics is as PC-run software designed to simplify operation and streamline data management. Here is how it works.

To service a battery, the user clicks the mouse on the desired battery selected from a database of over 2000 entries. Connected through a serial link, the PC configures the analyzer(s) to the correct battery parameters. The user inserts the battery and service commences.

Another method is scanning the bar code on the battery containing the model number. The software fetches the correct configuration code from the database and programs the analyzer. Motorola and other manufacturers identify their batteries with bar code labels.

For battery fleet operators, keeping track of a large battery fleet can be difficult, especially when observing the periodic maintenance requirements. Batteryshop™ simplifies management of such a system with the following setup:

Each battery is marked with a permanent bar code label containing a unique battery ID number. When servicing the battery, the user scans the battery ID and the analyzer configures itself to the correct battery setting through the PC. All battery test results are stored and updated in the database under the assigned battery ID number. Any reference to this battery in terms of performance, maintenance history and even vendor information is available with a click of a mouse. This feature enables the operator to retain battery records from birth to retirement.  Figure 7 illustrates such a system.

Figure 7:  Cadex Batteryshop™  
can be operated with one analyzer or a fully extended system of 120 analyzers servicing 480 batteries simultaneously. Point and click technology programs the analyzer by selecting the battery from the database. The software stores the battery test results for future evaluations.

Summary

Even the most advanced battery will weaken over time. The level of deterioration depends on battery type, use, level of maintenance and handling. With no system to remove weak batteries at the appropriate time, the benefit of expensive, ultra-high capacity batteries is defeated.

Implementing battery maintenance is the key to assuring long and reliable service. Usually, batteries get serviced only when they no longer hold charge or when the equipment is sent in for repair. As a result, battery-operated equipment becomes unreliable and battery-related failures often occur. The loss of adequate battery power is as detrimental as any other malfunction in the system.

Implementing a battery maintenance plan requires an effort by management to schedule periodic battery service. This task should become an integral component of an organization’s overall equipment maintenance and repair standard. A properly managed program improves battery performance, enhances reliability and cuts replacement costs

This article contains excerpts from the second edition book entitled Batteries in a Portable World — A Handbook on Rechargeable Batteries for Non-Engineers. In the book, Mr. Buchmann evaluates the battery in everyday use and explains their strengths and weaknesses in laymen’s terms. The 300-page book is available from Cadex Electronics Inc. through book@cadex.com, tel. 604-231-7777 or most bookstores. For additional information on battery technology visit www.buchmann.ca.

About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Richmond (Vancouver) British Columbia, Canada. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. The author of many articles and books on battery maintenance technology, Mr. Buchmann is a well-known speaker who has delivered technical papers and presentations at seminars and conferences around the world.

About the Company
Cadex Electronics Inc. is a world leader in the design and manufacture of advanced battery analyzers and chargers. Their award-winning products are used to prolong battery life in wireless communications, emergency services, mobile computing, avionics, biomedical, broadcasting and defense. Cadex products are sold in over 100 countries.