Chapter 12: Battery Maintenance Equipment
With the increasing volume of batteries in circulation, battery manufacturing is outpacing the supply of suitable equipment to test these packs. This void is especially apparent in the mobile phone market where large quantities of batteries are being replaced under warranty without 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 conditioning these batteries is 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 numbers of batteries, the function of battery test equipment is changing. Lengthy cycling is giving way to quick testing, improved battery preparation and better customer service. This shift in priority is especially apparent in the rapidly growing consumer market. In this chapter we examine modern battery analyzers and how they adapt to the changing needs of battery service.
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 charger models feature one or several bays with discharge opportunity. More advanced chargers include a display to reveal the capacity.
Some chargers offer pulse charge methods. This is done to improve charge efficiency and reduce the memory phenomenon on nickel-based batteries. Optimal 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 charge method promotes high surface area on the electrodes and helps in the recombination of the gases generated during charge.
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 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, the pulse charge method alone is not sufficient and a full discharge or recondition cycle is needed to break down the more stubborn crystalline formation.
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. One of the main advantages of the programmable battery analyzer is the ability to test the batteries against preset parameters.
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 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. On the low end of the scale, a problem may arise if a 400mAh battery is serviced. This battery may not be capable of accepting a charge rate higher than 1C and the battery could be damaged.
When purchasing a battery analyzer, there is a tendency to buy according to 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 12-1 illustrates an advanced battery analyzer. [12.1]
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 address different battery needs. The Cadex 7000 Series features ‘Prime’ to prepare a new battery for field use and ‘Auto’ to test and recondition weak batteries from the field. ‘Custom’ allows the setting of unique cycle sequences composed of charge, discharge, recondition, trickle charge or any combination, including rest periods and repeats.
More and more battery analyzers now measure the internal battery resistance, a feature that enables one to test a battery in a few seconds. The resistance check works best with lithium-based batteries because the level of internal cell resistance is in direct reflection to the performance. The resistance measurements can also be used for NiMH batteries but the readings do not fully disclose the battery’s condition.
One of the most powerful features offered in modern battery analyzers is battery quick testing. Within two to five minutes, reasonably accurate state-of-health (SoH) readings are available. The test is independent of the state-of-charge (SoC). Some charge is needed, however, to facilitate the test.
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, which receives a large number of batteries under warranty. With the proper equipment, many of these presumably faulty batteries can be jump-started instead of replaced.
To accurately test batteries that power digital equipment, a modern battery analyzer is 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 a slower motion to accommodate the load signals. Pulse duration of 5 ms, or ten times slower than the true GSM, is commonly used.
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 different load conditions, calculating the predicted runtime in the absence of a battery analyzer would be difficult.
Easy operation is an important feature of any battery analyzer. This quality is appreciated because the user is confronted with an ever-increasing number of battery types. Displaying the battery capacity in percentage of the nominal capacity rather than in milliampere-hours (mAh) is preferred by many users. With the percentage readout, the user does not need to memorize the ratings of each battery tested because this battery 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 attached right to the battery.
A battery analyzer should be automated and require minimal operator time. The task of the operator 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. Properly used, a battery analyzer generates major cost savings in terms of longer battery life and more dependable service.
Battery Analyzers for Maintenance-Free Batteries
In the past, the purpose of battery analyzers was to restore NiCd batteries affected by ‘memory’. With today’s nickel-free batteries, memory is no longer a problem and the modern battery analyzer assumes duties other than conditioning weak batteries. In an environment with nickel-free batteries, the purpose of an analyzer is shifting to performance verification, quality control, quick testing and quick priming.
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 and a warranty claim can be made if the capacity drops below the specified level toward the end of the warranty period.
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. Many of today’s battery 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, this battery chemistry 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 this problem.
Before adding new batteries to the battery fleet, a battery analyzer can be used to perform a spot check to ensure proper operation. If a battery shows low performance due to aging, the inventory practices may be changed to the ‘just in time’ method. Storage facilities with improved temperature control may also be sought.
An important new function of a battery analyzer is the ability to quick test batteries. No longer is it necessary to guess a battery’s condition by reading the terminal voltage, measuring the internal resistance or in enrolling lengthy charge and discharge cycles to determine its performance. Modern quick test programs using artificial intelligence are amazingly accurate and work independently of SoC.
Battery quick testing is finding a ready market niche with mobile phone dealers. This feature saves money because batteries returned under warranty can be tested. Replacements are only issued if a genuine problem is found. Once battery quick testing has been further refined, this technology will also find applications in the fields of biomedical, broadcast, aviation and defense.
The quantity of batteries which an analyzer is capable of servicing depends on the number of battery bays available. The type of service programs and the conditions of the batteries serviced also play a role. 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.
The four-station Cadex 7400 battery analyzer is capable of processing four nickel-based batteries every 4 to 8 hours on a full-service program. 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 to be restored 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 require the least amount of time. The Cadex Quicktest™ available on the Cadex 7000 Series takes three minutes per battery. The time is prolonged if a brief charge or discharge is needed prior to testing. A charge or discharge is applied automatically if the battery resides outside the SoC requirements of 20 to 90 percent. Unlike the maintenance program, the Cadex Quicktest™ does not improve the battery’s performance; it simply measures its SoH.
The Ohmtest™measurement of the Cadex 7000 Series analyzer takes ten seconds to complete. 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 which affect the accuracy of the internal resistance readings, one of which is SoC and the settling time allowed immediately after a recharge. A newly charged battery exhibits higher resistance readings compared to one that has rested for a while. The increased interfacial resistance present after charging causes this. 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
Organizations servicing portable equipment need simplified battery testing. The difficulty of testing batteries is brought on by the proliferation of batteries, both in volume and diversity of models. With most standalone battery test equipment, servicing batteries with conventional methods is complex and time consuming. This task will only get more difficult as new battery models are added, almost weekly. New chemistries are being introduced which have different service requirements.
Manufacturers of battery test equipment are responding by introducing software packages that run on a PC. Many new systems enable operating the battery analyzers through a PC. 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 settings, and stores the test results obtained from the batteries. Figure 12-2 illustrates such a battery maintenance system. [12.2]
Here are examples of how a computer-assisted battery testing system can simplify operation. To service a battery with Cadex Batteryshop™, for example, the user selects the battery model from the database, clicks the mouse, and the analyzer is automatically configured to the correct battery parameters. Programming the analyzer by scanning the bar code identifying 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.
For battery fleet operators, keeping track of a large battery fleet can be difficult, especially when observing the periodic maintenance requirements. With systems such as Cadex 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 this is done:
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 automatically configured 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.
Delivering 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.
Cadex Batteryshop™, includes specialty programs that may not be available on other software products. For example, the program allows discharging a battery under a given pulsed current to simulate digital load requirements. Other programs include life cycling to evaluate the battery’s longevity, self-discharge tests, quick formatting and priming. The Internet allows updating the battery database to include new entries, fetching battery matrix settings for quick testing, sending battery test results to a central location, and downloading of new firmware for the Cadex 7000 Series battery analyzers.