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Battery Testers for Modern Batteries for Mobile Devices 

Isidor Buchmann, President, Cadex Electronics Inc. isidor.buchmann@cadex.com
(August 2001)

Rechargeable batteries are known to cause more concern, grief and frustration than any other part of a portable device. Given its relatively short life span, the battery is also the most expensive and least reliable component.

How are batteries checked and serviced? This article describes the advancements of the modern battery analyzer and how these instruments are used in industry. While organizations such as public safety have been using battery analyzers for many decades to restore and prolong nickel-cadmium batteries, battery analyzers are beginning to make their way into the mobile phone market. Early models were impractical and did not adapt to the rapidly changing pool of batteries. In addition, the analyzers were complex and did not offer the quick and accurate service customers demanded.

The last few years have brought a rebirth in battery analyzer technology. Gone are the units that do nothing more than cycle batteries. With the move from high-maintenance nickel-based batteries to lithium-based batteries that no longer require periodic discharges, the duty of a battery analyzer is changing from extending battery life to quick testing and quick fixing.

There are two basic types of battery analyzers: fixed current and programmable. While fixed current units are less expensive and generally simpler to operate, programmable analyzers are more accurate and faster. Programmable units allow better adaptation to different battery needs and are more effective in restoring weak batteries. The ability to quick test batteries is reserved for the programmable units only.

From a technical point of view, the two analyzers function as follows: Inserting a battery into a fixed current device commences service at a fixed charge and discharge current of about 600mA. Smaller batteries get serviced reasonably fast but larger batteries are slow. The service time of an 1800mAh battery is three times that of a 600mAh pack. The capacity readout is in mAh and reflects the length of discharge. In comparison, the programmable units service the battery against preset parameters. The readout is usually in percentage of the nominal battery capacity.

The programmable battery analyzer

The programmable battery analyzer retains battery settings and test parameters in the system, commonly in the battery adapters. This allows batteries to be serviced to manufacturer’s specified settings. Figure 1 illustrates a programmable battery analyzer.

Battery-specific adapters are available for all major batteries. User-programmable cables with alligator clips accommodate batteries when no adapter is on hand. For service centers, a universal battery adapter eliminates the need for custom adapters. Two contact probes mounted on flexible arms provide the connection when they are lowered to the battery terminals. Magnetic guides keep the battery in position.

Figure 1: Cadex 7400 battery analyzer

The Cadex 7400 services nickel, lead and lithium-based batteries. The analyzer is programmable to a wide range of voltage and current settings. Custom battery adapters simplify the interface of different battery types. The Quicktest™ 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.

Advanced battery analyzers are capable of evaluating battery condition and implementing corrective service to restore performance. On nickel-based systems, a recondition cycle is applied automatically if a user-selected target capacity cannot be reached.

User-selectable programs service different battery needs. On the Cadex 7000 Series for example, Prime prepares a new battery for field use and Auto tests and reconditions weak batteries. Custom allows the setting of unique cycles composed of charge, discharge, recondition, trickle charge or any combination, including rest periods and repeats.

Advanced battery analyzers are capable of measuring internal battery resistance. Obtained in a few seconds, resistance readings work well with lithium-based batteries because the cell resistance is in direct relationship to performance. Internal resistance readings can also be used for nickel-based batteries, however, the results do not accurately disclose the battery’s state-of-health.

To increase precision, advanced battery analyzers offer quick test programs. The Cadex Quicktest™ works using artificial intelligence algorithms, which adapt to new battery types through learn cycles. The more learn cycles from batteries with varying capacities are completed, the more accurate the readings will be. Learn matrices are stored in the battery adapters and are added at time of manufacturing.

The Cadex Quicktest™ is performed with battery charge levels of 20 to 90 percent. If outside this range, the analyzer automatically applies a brief charge or discharge to bring the battery within testing range. The test lasts three minutes, longer if preparation is needed. The charge level does not affect the reading.

Batteries are often discarded, even when restoration is possible. Mobile phone dealers have confirmed that 80 to 90 percent of returned mobile phone batteries can be repaired with a battery analyzer. But most dealers are not equipped to handle the influx of batteries returned under warranty. They are sent back to the manufacturers or are discarded without attempting to restore them.

To better serve the needs of the mobile phone industry, advanced battery analyzers include quick fix programs consisting of ultra-fast charging and power boosting. For example, Cadex Boost is able to wake up Li-ion batteries that have become unserviceable due to very low discharge. The program applies a gentle charge to activate the protection circuit and raise the voltage to operation levels.

Unlike the even current flow reminiscent of analog devices, digital equipment loads the battery with hefty current bursts. The Global System for Mobile Communications (GSM) transmits voice data in 567 m s bursts with pulse currents of 1.5 amperes and higher.

Modern battery analyzers are capable of simulating digital loads, allowing battery testing under field conditions. It should be noted, however, that not all analyzers are capable of reproducing the short GSM current bursts. Medium-priced units often use lower frequencies. The capacity readings are slightly higher when discharged at lower frequencies than in real time. A simulated pulse discharge, even if done at lower frequencies, provides more accurate readings than direct current (DC).

Most analyzers print service reports and battery labels. This feature simplifies maintenance, especially in a fleet environment where operators must observe periodic service requirements. Labeling batteries with the last service date reminds the user when the next service is due. Labeling works well because the basic service history is available where it is needed most — on the battery.

 

PC software

Some battery analyzers are available with software for PC interface. This option expands the functionality of battery analyzers, simplifies operation and allows users to perform complex and accurate battery tests with minimal training. In addition, PC software enables design engineers to collect and store valuable battery information by running customized test programs.

Cadex Batteryshop™ is a Widows-based software that works in conjunction with Cadex 7000 Series battery analyzers. Although the analyzers are stand-alone units, the software overrides the analyzers when connected to a PC. To service a battery, the user selects the battery model from the database and clicks the mouse. The PC configures the analyzer to the correct parameters, ready to service the battery. Programming the analyzer by scanning the battery model is also possible.

Fleet batteries are serviced by first marking all packs with a unique battery ID number. Batteryshop™ generates these labels in bar code format. The user scans the battery ID and the analyzer is automatically programmed 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 the battery in terms of performance, maintenance history and vendor information is available with a click of the mouse. This feature enables retaining battery records from birth to retirement.

Batteryshop™ also assists battery manufacturers and pack assemblers. Among typical applications are: life cycle testing, batch checking for quality control and documenting warranty claims. Chemistry, voltage and current setting are entered manually through the PC. Charge, discharge and temperature curves can be displayed in real-time graphics.

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

Summary

Battery analyzers have found two distinct market applications: first to maintain and restore fleet batteries for established battery users such as the public service sector, and second to check and repair personal batteries used in mobile phone and related markets. The second application requires a more complex model because of the large variety of batteries in circulation and the diversity of user groups.

Manufacturers of battery analyzers are experimenting with new ideas to simplify battery testing. Proven models from other industries are being evaluated. One such model is the automated checkout system of a supermarket. Here, the clerk is relieved of memorizing detailed product information to complete the transaction. This knowledge is embedding in the system. Up-to-the-second inventory status is available at any time.

Embedded systems will also help to streamline battery testing. This is especially pertinent for larger service centers and businesses that operate internationally. The task of global training is simplified when complex functions and procedures can be included in a user-friendly package. Retaining test results at a central location is another benefit such a system provides.

Reference: 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 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 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.


Related Resources:
> Battery Issues in Mobile/wireless 

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