Battery Test Equipment

Batteries are commonly tested by measuring the capacity through a full discharge. While voltage and internal resistance provide a rough indication of the battery condition, these readings do not disclose the capacity, the leading health indicator of a battery. Voltage and resistance tend to reveal anomalies only when the battery is in a fault mode. Most batteries keep a normal voltage and low resistance while the capacity gradually fades with age. Read about How to Measure Internal Resistance.

There is a move towards rapid testing, however, current methods only provide an estimation of the battery performance and the results can be in accurate. Rapid-test methods work best with single-cell Li-ion packs; series and parallel connection of cells can distort the readings. Public safety, medical and defense organizations still apply a periodic full discharge/charge cycles, and this is normally done with a battery analyzers.

Battery Analyzer

Battery analyzers became popular in the 1980s and 1990s to restore nickel-cadmium batteries affected by “memory.” Today, battery analyzers serve in identifying packs that no longer meet requirements; they form a vital part in maintaining fleet batteries. Read about How to Maintain Fleet Batteries. Typical battery analyzers are the Cadex C7000 Series, workhorses that serve a broad range of batteries. These devices accommodate lead-, nickel- and lithium-based batteries, feature automated service programs and operate in stand-alone mode or with PC software.

Figure 1: Cadex C7400ER battery analyzer Four-station battery analyzer services batteries of up to 36V and 6A per station. Custom and universal battery adapters accommodate lead-, nickel- and lithium-based batteries. Courtesy of Cadex

The Cadex analyzers include Custom programs in which the user sets a unique sequence of charge, discharge, recondition, wait and repeat. The Lifecycle program cycles battery until the capacity drops to the preset target capacity while counting the delivered cycles. OhmTest measures the internal battery resistance, and Runtime discharges at three different current levels to test battery runtimes within a simulated user pattern. QuickSort™ sorts lithium-ion batteries in 30 seconds into Good, Low and Poor; Boost reactivates packs that fell asleep due to over-discharge. Further programs include Self-Discharge to measure losses in 24 hours, and Prime to prepare new and stored batteries for field use.

Connecting the batteries for service has always been a challenge. Cadex solved the battery interface with the SnapLock™ adapter system consisting of custom adapters for common batteries and universal adapters for specialty packs. The custom adapters are easiest to use as they are designed for a battery type and the pack can go in only one way. The adapters include configuration codes that store up to 10 unique battery types and feature a thermistor to monitor temperature. Installing the adapter configures the analyzer to the correct setting. Editing is possible with analyzer’s menu function or via the PC-BatteryShop software. See Cadex's list of available adapters.

With the proliferation of cellular batteries and the need for a quick and simple battery interchange, Cadex developed the RigidArm™. This universal battery adapter features spring-loaded arms that meet the battery contacts from the top down. Read about How to Service Mobile Phone Batteries.  A third option is the Smart Cables (Figure 3) featuring alligator clips and a temperature sensor to monitor battery temperature.

Figure 3: Programmable Smart Cable The cable stores 10 different battery types; programming is by menu or via PC-BatteryShop™ software; a thermistor monitors temperature.. Courtesy of Cadex

With PC-BatteryShop™ software (Cadex), the PC becomes the master and the analyzers the slave. Clicking the mouse on any of the 2,000 batteries listed in the database or swiping the bar code on the battery label configures the analyzer to the correct setting. You can extend the library by adding new battery models or downloading the latest listing from the Cadex website. PC-BatteryShop™ software is optional; it displays the readings and real-time graphic and is designed to operate 32 analyzers for simultaneous service of 128 batteries (with most PCs).

Figure 4: PC-BatteryShop™ software provides practical PC-interface to control and monitor Cadex C7000 Series battery analyzers. The monitor provides real-time graphic; the system stores vital data.

Courtesy of Cadex

While battery analyzers are primarily used as a service tool, battery test systems provide multi-purpose test functions for research laboratories. Typical applications are life-cycle and stress-testing to verify batteries for field use. Much of this testing can be automated.  

The Cadex C8000 (Figure 4) is such an automated battery test system. You can measure the battery runtimes by capturing and storing load signatures from mobile phones, laptops, power tools and electric drivetrain and then replicate the load condition in the lab. A further test involves checking the longevity of a battery under the discharge conditions reminiscent in the field. SMBus capability displays the register settings of a smart battery to read flags and to check for correct function. If higher discharge currents than 10A are needed, the C8000 connects to designated external load banks. The C8000 forms a laboratory system that controls environmental chambers, monitors analog signals and triggers user-set alarm conditions. PC-BatteryLab™ software provides interface to a PC for the control and monitoring of up to 8 units to service 32 batteries independently (with most PCs).

Figure 4: Cadex C8000 Battery Test System Four independent channels provide up to 10A each and 36V. Maximum charge power is 400W, discharge is 320W. The discharge power can be enhanced with external load banks. Courtesy of Cadex

The alternate to a battery test system is a programmable power supply controlled by a computer. Such a platform offers high flexibility but requires careful programming to prevent stress to the battery and avoid damage or fire, should an anomaly occur. A battery test system, such as the Cadex C8000, offers protected charge and discharge programs that will identify a faulty battery and terminate a service safely. The system can be overridden to perform destructive tests, however.