Battery testers for modern batteries

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

April 2001

With the demand for batteries rapidly growing, battery manufacturing may be outpacing the supply of suitable equipment to test them. This void is apparent in the mobile phone market where large quantities of batteries are being returned under warranty. Many are discarded without first checking or attempting to restore them. The dealers are simply not equipped to handle the influx of returned batteries, neither is the staff trained to perform this task on a customer service level. Testing and restoring batteries has become a complex procedure that lies outside the capabilities of most customer service clerks.

With the move to maintenance-free batteries and the need to test larger volumes of batteries, battery test equipment is shifting to quick testing and boosting. In this article we examine the duty of the modern charger and battery analyzer, and observe how well these units satisfy the current demands.

Conditioning Chargers

Charging batteries is often not enough, especially when it comes to nickel-based chemistries. Periodic maintenance is needed to optimize battery life. Some innovative manufacturers offer chargers with conditioning features. The most basic models provide one or several bays with discharge capability. More advanced chargers include a display to reveal the battery capacity. Discharging lithium-based batteries for the purpose of prolonging life is neither necessary, nor advisable.

Some chargers offer pulse charge methods. This is done to improve charge efficiency and reduce the memory phenomenon on nickel-based batteries. Improved charge performance is achieved by using a pulse charge that intersperses discharge pulses between charge pulses. Commonly referred to as ‘burp’ or ‘reverse load’ charge, this method promotes high surface area on the electrodes and helps recombine the gases generated during charge. Pulse charging benefits mainly Nickel-based batteries.

Some manufacturers claim that the pulse charge method conditions and restores NiCd batteries and makes the periodic discharges redundant. Research carried out by the US Army has revealed that pulse charging does indeed reduce the crystalline formation on the NiCd battery. If properly administered, batteries charged with these pulse chargers prolong service life. For batteries with advanced memory, however, a full discharge or recondition cycle is needed to break down the more stubborn crystalline formation.

Battery Analyzers

There are two types of battery analyzers: the fixed current units and the programmable devices. While fixed current units are less expensive and generally simpler to operate, programmable analyzers are more accurate and faster. Programmable units can better adapt to different battery needs and are more effective in restoring weak batteries.

Fixed current analyzers perform well in organizations that use medium size batteries ranging from 600mAh to 1500mAh. If smaller or larger batteries are serviced, the charge and discharge currents are compromised and the program time is prolonged. Here is the reason why.

A fixed current battery analyzer with a charge and discharge current of 600mA, for example, services a 600mAh battery in about three hours, roughly one hour for each cycle starting with charge, followed by discharge and a final charge. Servicing an 1800mAh battery would take three times as long. A very small batteries, say a 400mAh, may not be capable of accepting a charge rate that is higher than 1C and the battery could sustain damage.

When purchasing a battery analyzer, there is a tendency to buy on price. With the need to service a larger volume of batteries of a wider variety, second-generation buyers find the advanced features on upscale models worth the extra cost. These features manifest themselves in reduced operator time, increased, throughput, simpler operation and the use of less trained staff. Adaptation to new battery systems is also made easier. Figure 1 illustrates an advanced battery analyzer made by Cadex Electronics.

An advanced battery analyzer evaluates the condition of a battery and implements the appropriate service to restore the battery’s performance. On nickel-based systems, a recondition cycle is applied automatically if a user-selected capacity level cannot be reached.

Battery chemistry, voltage and current ratings are user-programmable. These parameters are stored in interchangeable battery adapters and configure the analyzer to the correct function when the adapter is installed. In the Cadex 7000 Series battery analyzers, for example, each adapter is preprogrammed with up to ten distinct configuration codes (C-codes) to enable service for all batteries with the same footprint.

Battery-specific adapters are available for all major batteries; user-programmable cables with alligator clips accommodate batteries for which no adapter is on hand. Batteries with shorted, mismatched or soft cells are identified in minutes and their deficiencies are displayed on the LCD panel.

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

Many battery analyzers are capable of measuring the internal battery resistance. Obtained in only a few seconds, the resistance reading works well with lithium-based batteries because the level of cell resistance is in direct relation to the performance. Internal resistance readings can also be used for nickel-based batteries, however, the readings do not accurately disclose the battery’s condition.

More accurate methods are achieved by using quick test programs. The Cadex Quicktest™ is based on fuzzy logic and lasts about three minutes. Good results are achieved with three learn cycles taken from batteries of different SoH readings. The matrices from the learn cycles are stored in the adapters. Most battery adapters are equipped with the matrices when purchased.

New requirements of battery analyzers are the ultra-fast charge and quick prime features. When a battery is inserted, the analyzer evaluates the battery, applies an ultra-fast charge if needed, and prepares the battery for service within minutes. Such a feature helps the mobile phone industry to handle the large number of warranty return batteries. With the right equipment, many of these presumably faulty batteries can be jump-started and given back to the customer instead of being replaced.

To accurately test batteries that power digital equipment, modern battery analyzers are capable of discharging a battery under a simulated digital load. The GSM waveform, for example, transmits voice data in 567 ms bursts with currents of 1.5A and higher. By simulating these pulses, the performance of a battery can be tested under these field conditions. Not all analyzers are capable of simulating such short current bursts. Instead, medium-priced battery analyzers use lower frequencies.

Another application involving uneven load demand is the so-called 5‑5‑90 program used to simulate the runtime of analog two-way radios. The battery is loaded 5 percent of the time on transmit, 5 percent on receive and 90 percent on standby. Other combinations are 10-10-80. Each stage can be programmed to the appropriate discharge current. Because of the complex load conditions, calculating the predicted runtime in the absence of a battery analyzer would be difficult.

Easy operation is an important attribute of any battery analyzer. Displaying the battery capacity in percentage of the nominal capacity rather than in milliampere-hours (mAh) is preferred by many. With the percentage readout, the user does not need to memorize the ratings of each battery tested because this information is stored in the system. The percentage readout allows an added level of automation by implementing a recondition cycle if the set target capacity level cannot be reached.

Some analyzers are capable of setting the appropriate battery parameters automatically when a battery is inserted. An intelligent battery adapter reads a passive code that is imbedded in most batteries. The code may consist of a jumper, resistor or specified thermistor value. Some battery packs contain a memory chip that holds a digital code. On recognition of the battery, the adapter assigns the correct service parameters. Automatic battery identification minimizes training and allows battery service by untrained staff.

Most analyzers are capable of printing service reports and battery labels. This feature simplifies the task of keeping track of batteries. Marking batteries with the service date reminds the user when a battery is due for service. Labeling works well because the basic service history is available where it is needed most — on the battery.

A battery analyzer should be automated and require minimal operator time. His or her task should be limited to scheduling incoming batteries for testing, marking the batteries after service, and replacing those that did not meet the performance criteria. Occasional selection of the correct current rating and chemistry may also be necessary.

Battery Analyzers for Maintenance-Free Batteries

One of the main purposes of a battery analyzer has been to restore NiCd batteries affected by ‘memory’. With today’s nickel-free batteries, memory is no longer a problem and the analyzer assumes additional duties. These are performance verification, quality control, quick testing, quick priming and boosting batteries that have been discharged too deeply.

Common sense suggests that a new battery should always perform flawlessly. Yet even brand new batteries do not always meet manufacturer's specifications. With a battery analyzer, all incoming batteries can be checked as part of a quality control procedure. Warranty claims are applied if the capacity drops below the specified level on the warranty expiry date.

The typical life of a Li‑ion battery is 300 to 500 discharge/charge cycles or two to three years from the time of manufacturing. The loss of battery capacity occurs gradually and often without the knowledge of the user. The function of the battery analyzer is to identify weak batteries and “weed’ them out before they become a problem.

A battery analyzer can also trouble-shoot the cause of short runtimes. There are several reasons for this common deficiency. In some cases, the battery may not be properly formatted when first put in service, or the original charger does not provide a full charge. In other cases, the portable device draws more current than specified. A common problem is high internal battery resistance. Many analyzers can simulate the load signature of a digital device and verify the runtime according to the load requirements.

Lithium-based batteries are sensitive to aging. If stored fully charged and at elevated temperatures, the battery deteriorates to a 50 percent performance level in about one year. Similar performance degradation can be seen on NiMH batteries when used under these conditions. Although still considered new, the user will likely blame the equipment rather than the battery for its poor performance. The analyzer can isolate such problems.

Battery Throughput

The quantity of batteries an analyzer can process in a given time depends on the number of bays available, the type of service programs required and the conditions in which the batteries are in. Li‑ion and lead acid batteries take longer to charge than nickel-based packs. Analyzers with fixed charge and discharge currents require added time, especially for larger batteries.

On a full-service program, the four-station Cadex 7400 battery analyzer is capable of processing four nickel-based batteries every 4 to 8 hours. Based on two batches per day (morning and evening attendance) and 20 working days per month, one such analyzer can service 160 batteries every month. The throughput of batteries with ratings higher than 2000mA or those that need to be charged and discharged at lower C‑rates will take longer. To allow extra analyzer capacity, including reconditioning of old batteries, one four-station analyzer is recommended for a fleet of 100 batteries.

When first servicing a fleet of batteries with a battery analyzer, extra runtime will be required, especially if a large number of batteries need restoration with the recondition cycle. Once the user-defined target capacity has been reached, maintaining that level from then on will be easier and take less time. When first installing a battery maintenance program, some older packs will likely need replacing because not all batteries recover with exercise and recondition programs.

Quick test methods offer much higher throughputs than full service programs. The Cadex Quicktestä takes three minutes per battery but the time can be longer. A charge or discharge is applied automatically if the battery resides outside the state-of-charge requirements of 20 to 90 percent. Unlike the maintenance program, quick testing does not improve the battery’s performance; it simply measures its state-of-health.

With a completion time of only ten seconds, the Cadex Ohmtest™ provides the fasted measurement. Large numbers of batteries can be examined if the packs are charged prior to the test. Measuring the internal battery resistance works reasonably well if reference readings are on hand. However, there are batteries that measure good internal resistance but do not perform well. This is especially common with nickel-based chemistries.

There are a number of factors that affect the accuracy of the internal resistance readings, one of which is the state-of-charge and the resting time immediately after a charge. A newly charged battery exhibits higher resistance readings compared to one that has rested for a while. Allow the battery to rest for one hour or more before measurement. Temperature and the number of cells connected in series also affects the readings. Many batteries contain a protection circuit that distorts the readings further.

Battery Maintenance Software

Testing batteries with conventional methods is becoming increasingly more complex. This situation is made more difficult as new batteries are added almost daily. In addition, new chemistries are being introduced that have different service requirements.

Manufacturers of battery test equipment are responding to the changing requirements by introducing software packages that run on a PC. Properly designed, such products bring battery maintenance within reach of the untrained operator.

Cadex Batteryshop™ is a system that integrates with the Cadex 7000 Series battery analyzers. Although the analyzers are stand-alone units that can think on their own, the software overrides the analyzer to adjust the parameter settings. Figure 2 illustrates such a battery maintenance system.

Figure 2:  Components of a battery maintenance system.
Cadex Batteryshop™  stores the battery test results on the database. Point and click technology programs the analyzer by selecting the battery from a database. The system accommodates up to 120 analyzers.

To service a battery with Cadex Batteryshop™, the user selects the battery model from the database, clicks the mouse and the analyzer is automatically configured to the correct battery parameters. The user then inserts the battery and the service commences. Programming the analyzer by scanning the bar code with the battery’s model number is also possible.

In the near future, the operator will be able to view a picture of the battery on a PC monitor. Clicking on the image will reveal the various models available in that battery family. Clicking on the correct model will program the analyzer, ready to service the battery.

For battery fleet operators, keeping track of a large battery fleet can be difficult, especially when observing the periodic maintenance requirements. With Batteryshop™, the battery test results can be stored in the database. This feature enables the operator to retain battery records from birth to retirement. Here is how it works:

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 is programed 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 vendor information is available with a click of a mouse.

Producing batteries with consistent high quality is a concern for all battery manufacturers and distributors. With advanced battery maintenance systems, battery batches can be tested and documented to satisfy quality control standards. Voltage, current and temperature information can be displayed in real-time graphics.

The Internet plays a pivotal role in battery testing. Batteryshop™ enables downloading battery matrix settings from a Cadex database for quick testing; sending battery test results to a central location, and downloading new firmware to upgrade existing equipment. 

Summary

Battery analyzers have found two distinct market applications: They are [1] maintaining and restoring fleet batteries in the public service sector, and [2] checking and quick-fixing consumer batteries such as those used on mobile phones. The later is the more complex application because of the vast variety of battery types and the diverse user base in which they are employed in.

To streamline battery testing, working models from industrial applications can be implemented. Such a model would contain the test parameters in the system and perform the task normally done by an operator automatically. Similar to a checkout clerk in a supermarket who, in the pre-computer days, required full product knowledge, can now rely on the bar code information. The price of all items purchased is flashed on the screen and an up-to-the-second inventory status is available. Such simplifications are also possible in servicing batteries.  

Properly used, a battery analyzer generates major cost savings in terms of prolonged battery life, improving dependability, reducing warranty returns and increasing customer satisfaction.

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.