The changing demands of modern battery testers

Isidor Buchmann
Cadex Electronics Inc.
isidor.buchmann@cadex.com
www.buchmann.ca
December 2001

One of the main purposes of a battery analyzer has been to exercise and restore NiCd batteries affected by 'memory'. With today's nickel-free batteries, memory is no longer a problem. Lithium-based batteries do not need a periodic discharge; neither can these batteries be restored through cycling when weak.

In this article we examine some of the new duties the modern battery analyzer assumes. These include performance verification through quick testing, energizing batteries that have fallen asleep due to deep discharge and priming new batteries.

Common sense suggests that a new battery should always perform flawlessly, yet many packs fail to meet manufacturer's specifications. With a battery analyzer, incoming batteries can be checked as part of quality control. Packs that perform poorly during the warranty period can be identified and returned for replacement.

The typical life of a Li?ion battery is 300 to 500 discharge/charge cycles or two to three years from time of manufacturing. The loss of battery capacity occurs gradually and often without the awareness of the user. The function of the battery analyzer is to identify weak batteries and "weed" them out before they become a problem. This task is especially pertinent in a fleet environment. The loss of adequate battery power is as detrimental as any other malfunction in the system.

A battery analyzer can also trouble-shoot short runtime. This is a common complaint and there are multiple causes that contribute to this problem. In some instances, the battery may not be properly formatted when first put in service. Repeated cycling can correct this. Another problem is incomplete charge when charged with the original charger. A battery analyzer can help in comparing the capacity when charged with the original charger and then comparing it with a full charge provided by the analyzer.

Another common cause of short runtime is high internal battery resistance brought on by use and aging. Many analyzers are capable of measuring the internal battery resistance. Some instruments can simulate the load signature drawn by a digital device to verify the runtime according to load requirements.

Higher than specified power consumption is another reason of short runtimes. This, however, is mostly related to the way the equipment is being used.

Lithium-based batteries are sensitive to aging. If stored fully charged at elevated temperatures, the battery can deteriorate to 50 percent capacity in about one year. Similar performance degradations are observed on NiMH batteries when used under the same conditions. Although still considered new, the user will blame the equipment rather than the battery for poor performance. The analyzer can isolate such problems quickly and accurately.

With the increased dependence on battery power, the need for battery quick testing becomes apparent. Various test schemes have been introduced over the years but none has caught on. Most have inherent problems with accuracy. The battery needs to be fully charged before testing because different charge levels interfere with the state-of-health readings. Defense organizations invest heavily in battery quick testing, only to come up with textbook methods that require large computers that must build up extensive data banks of reference material for each battery type checked. In addition, the test time is often too long to be practical.

Cadex Electronics has developed a technique that measures the state-of-health of a battery in three minutes. Based on inference technology, the Cadex Quicktest™ uses battery specific matrices that are derived through a "trend learning" process using artificial intelligence. The ability to self-learn enables the system to adapt to new battery chemistries without having to change hardware.

Figure 1: Cadex 7400 battery analyzer The programmable Cadex 7400 services Li?ion/polymer, NiMH, NiCd and lead acid batteries. Battery adapters simplify the interface with different battery types. A quick test program measures battery state-of-health in three minutes, independent of charge. Nickel-based batteries are automatically restored if the capacity falls below the user-defined target capacity.

Quicktest™ is available on the Cadex 7200 (two-station) and 7400 (four-station) battery analyzer/ reconditioners. The system accommodates Li-ion, NiMH, NiCd and lead acid batteries; the required charge level is 20 to 90 percent. If outside this range, the analyzer automatically applies a brief charge or discharge. The charge level within this acceptable range does not affect the state-of-health readings.

The matrix obtained through Learn is stored in the battery adapters that also contain the battery parameters to configure the analyzer. One Learn cycle is the minimum requirement to develop a working QuickTest™ matrix. Better results are achieved when learning several batteries with varying state-of-health conditions. Once attained, the matrix can be copied to other battery adapters. Testing a battery with a properly learned matrix achieves an accuracy of +/-5 percent on most batteries. Popular custom adapters offered by Cadex include the matrix at time of purchase.

The Cadex QuickTest™ helps customer service staff to examine batteries at point-of-sales. For service centers, QuickTest™ is capable of quickly separating serviceable batteries from those that exhibit genuine defects. A full maintenance program may be needed to repair those batteries that are serviceable.
A common Li-ion battery failure is caused by excessive low discharge. This deactivates the internal safety circuit and the battery appears dead. The Boost program of the Cadex 7000 Series analyzers applies a gentle current to energize the battery. Once the voltage reaches charging range, a full service program verifies the battery.

To prove the effectiveness of the Boost program, Cadex has tested a large number of supposedly dead Li?ion polymer batteries from various manufacturers. When first measured, these batteries had no voltage and appeared dead. Charging the packs in their respective chargers was unsuccessful. After boosting, most batteries accepted normal charge. The analyzer applied a full service program and attained capacities of 80 percent and higher in most batteries. All restored packs performed flawlessly when returned to service.

Boosting Lithium-based batteries is safe. However, if the cell voltage has fallen to 1.5 volts and has dwelled in that state for several days, a recharge should be avoided. A very deep discharge may form copper shunts in the cells, which can develop an electrical short. The Cadex battery analyzers identify such faults and terminate service.

Nickel-based batteries can also benefit from the Boost program. Older batteries or those with advanced cycle count exhibit high self-discharge, a condition that cannot be corrected. If activated with Boost and left unattended, the battery may revert back to its former state.

Connecting batteries to the analyzer

Connecting batteries for testing has been a challenge for technicians and engineers alike. Many so-called 'engineering specials' with springs and levers have appeared, only to disappear because of impracticality. Cadex solved the problem with the FlexArm™ adapter.

Snapped into the Cadex 7200 and 7400 battery analyzers, the FlexArm™ accommodates virtually any battery type. By lowering the two arms fitted with contact probes, narrow and awkwardly placed contacts can be reached. Magnetic guides keep the battery in any position, horizontally or vertically.

Figure 2: Cadex FlexArm. Snapped into the Cadex 7000 Series battery analyzers, the FlexArm™ establishes contact by lowering the arms to the battery. Magnetic guides keep the battery in position. The FlexArm™ stores up to 10 battery types, each of which can be given a unique name.

The Cadex FlexArm™ requires setting of battery chemistry, voltage and mAh rating. The Edit key on the Cadex battery analyzer prompts the user to enter the specifications. The battery setting is stored in the FlexArm™. There is room to store 10 individual battery types, each of which can be given a unique name.

To check batteries with the Cadex QuickTest™, a common matrix may be used for packs that have similar chemistry, voltage and capacity rating. This applies to cell phone batteries consisting of a single Li-ion cell. If the readings are inaccurate, a separate matrix will be required for these batteries.

The Cadex FlexArm™ is best suited for technicians dealing with constantly changing batteries. However, large groups of identical batteries (fleet environment) are best served with custom adapters. These adapters are programmed at the factory and do not require setting of battery parameters.

Using the FlexArm™ together with the Cadex BatteryShop™ software allows for some interesting simplifications. All the user does is clicking the mouse on the selected battery and the analyzer configures to the correct parameters, ready for service.

Programming the analyzer by scanning the battery model is also possible. The model number is matched with the listing in the battery database and the correct parameters are assigned. BatteryShop™ is capable of generating bar code labels on demand.

The Internet is poised to play a pivotal role in battery testing. Batteryshop™ will be able to fetch C-Codes and matrices of new batteries, send battery test results to a central location, and download firmware to upgrade existing equipment. Batteryshop™ is equally proficient supporting one analyzer or a fully extended system of 120 units.

Summary

With batteries flooding the market, the availability of suitable equipment to test them may outpace battery production. This void is especially apparent in the mobile phone market where large quantities of batteries are being returned under warranty. Many of these presumably faulty packs are discarded without checking or attempting to restore them. In the end, the customer will pay with higher prices.

Testing and restoring batteries has become a complex assignment. Battery analyzers must be simple to operate and allow customer service staff to perform the task without much training. Properly used, these instruments will assist in managing the influx of returned batteries. The quick-test feature can sort packs that are serviceable from those that exhibit genuine defects. PC software assists in programming the analyzer and keeping pace with new battery arrivals. The Internet makes updating easy.

Battery testing also serves public safety organizations, rental outfits and defense organizations. With the quick-test feature, a battery can be examined prior to releasing to a customer or assignment for a critical mission. Testing by applying a full charge and discharge cycle is simply not practical. Being able to verify battery performance on the fly, only those packs are released that are fit for the job.

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 batteries 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 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. designs and manufactures advanced battery chargers, analyzers and battery management software. The award-winning products are built with one goal in mind - to make batteries run longer. They find applications in wireless communications, emergency services, mobile computing, avionics, biomedical, broadcasting and defense. Cadex is ISO 9001 certified and the products are sold in over 100 countries.