Advanced battery analyzers

How are batteries checked and serviced? This article describes the advancements of the modern battery analyzer and explains how these instruments are used in the industry. While organizations such as public safety have been using battery analyzers for the last two decades to restore and prolong nickel-cadmium batteries, analyzers have made their way also into the cell phone, portable computing, medical and defense markets. The early models were impractical and did not adapt well to changing battery chemistries. In addition, the analyzers provided limited service and did not offer the quick test results and restoration capabilities customers demand today.

The last few years have brought a rebirth of the battery analyzer. With the move from the high-maintenance nickel-based batteries to the maintenance-free lithium-based packs, the duty of a battery analyzer is changing from life-extending cycling to rapid testing and boosting.

Fixed current analyzers
There are two basic types of battery analyzers: the fixed current and programmable versions. Fixed current units are the lower priced of the two, and charge and discharge a battery at a preset 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. The fixed-current analyzers are the predecessors of the programmable units.

Programmable analyzers
The programmable analyzers allow servicing the battery against preset parameters. The charge and discharge currents are adjusted according to the battery rating, and the voltage is set to flag batteries with incorrect voltages. These analyzers provide more accurate readings and enable higher battery throughput than fixed current units. In addition, programmable analyzers are better suited to service new battery systems and have proven to be more effective in restoring weak batteries. The Cadex C7000-Series are such programmable battery analyzers.

Battery adapters
Interfacing the batteries has always been a challenge with battery analyzers. Technicians have invented contraptions with springs and levers so complicated that only they themselves are able to operate. Everybody else stays away from them of fear.

Cadex solved the battery interface issue with the custom adapters for common batteries and the universal adapters for specialty packs. The custom adapters are the easiest to use and provide the most accurate test results. User-programmable cables accommodate larger batteries or assist when no adapter is on hand. Smaller batteries can be serviced with the Cadex FlexArm™. Two contact probes mounted on flexible arms provide the connection when lowered to the battery terminals. Magnetic guides keep the battery in position and a temperature sensor safeguards the battery. Figure 1 illustrates the Cadex FlexArm™.

Figure 1: 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 adapters contain a memory chip that configures the analyzer to the correct setting. Each adapter stores 10 battery configuration codes to service 10 different battery types. The parameters can be edited with a few keystrokes on the analyzer's keypad.

Service programs
Advanced battery analyzers are capable of evaluating battery conditions and implementing corrective service to restore weak performance. The Cadex system, for example, automatically applies a recondition cycle to nickel-based packs if a user-selected target capacity cannot be reached. Other programs include Prime to prepare a new battery for field use, Charge to allow fast-charge and Custom to apply unique cycles composed of charge, discharge, recondition, trickle charge or any combination, including rest periods and repeats.

Many modern analyzers also offer battery rapid test programs. This often requires entering the battery voltage and rating (in mAh). To obtain accurate readings, a battery-specific matrix may also be required. The Cadex QuickTest™ stores the matrix in the battery adapter, together with the configuration code. Installing the adapter sets the analyzer to the correct parameters, transparent to the user.

With the Cadex system, the matrix is commonly included when purchasing the adapter. If missing, scanning several batteries with various state-of-health conditions creates the matrix. The test time is 3 minutes and requires a charge level of 20-90%. If outside this range, the analyzer automatically applies a brief charge or discharge.

Many batteries are discarded, even when restoration is possible. Cell phone dealers have confirmed that 80-90% of returned mobile phone batteries can be repaired with a battery analyzer. However, most dealers are not equipped to handle the influx of warranty batteries and the packs are returned to the manufacturers for replacement or are discarded. Rapid test enables checking the battery while the customer waits. Minor battery problems can be corrected on the spot.

A typical failure of lithium-ion batteries is excessive low discharge. If discharged below 2.5 volts per cell, the internal safety circuit deactivates and the battery no longer accepts charge with a regular charger. An excessive low discharge can occur if the battery is not recharged for some time after a full discharge through extensive use.

The Cadex battery analyzers feature Boost, a program, which reactivates batteries that appear dead. Boost works by applying a gentle current to the battery to re-energize the safety circuit and raise the cell voltage. After reaching the operating voltage, the battery can be charged and tested normally. Boosted batteries perform flawlessly as long as a repeat deep discharge is avoided.

Printing
Most analyzers are capable of printing service reports and battery labels. This feature simplifies maintenance, especially in a fleet environment where the operators must observe periodic service requirements. Printed reports also benefit customer service staff and engineers.

Figure 2: Label printer. The label printer automatically spits out a label with each battery serviced. The labels contain the service date; service due date, battery capacity and internal battery resistance.

Labeling the batteries with service date and test results is self-governing in the sense that the user only picks a properly labeled battery and has recently been serviced. Batteries with past due service date are segregated for service. With such a system, the user has full confidence that the battery will last through the shift, with energy to spare. Weak batteries are weeded out.

About the Author
Isidor Buchmann is the founder and CEO of Cadex Electronics Inc., in Vancouver BC. Mr. Buchmann has a background in radio communications and has studied the behavior of rechargeable batteries in practical, everyday applications for two decades. Award winning author of many articles and books on batteries, Mr. Buchmann has delivered technical papers around the world.
Cadex Electronics is a manufacturer of advanced battery chargers, battery analyzers and PC software. For product information please visit www.cadex.com.