BU-906: Testing Nickel-based Batteries

Learn about test methods and what the limitations are.

Capacity-fade of nickel-based batteries correlates, in part, with a rise in internal resistance. NiCd and NiMH share similarities with lead- and lithium-based batteries in that the internal resistance remains low at first and then rapidly increases towards the end of life. Measuring resistance could serve as a simple rapid-test method to detect end-of-life but this would not provide dependable state-of-health (SoH)  information. (See BU-208: Cycling Performance).

QuickTest™ (by Cadex) goes deeper than mere resistance measurements and fuses data from six variables. These are capacity, internal resistance, self-discharge, charge acceptance, discharge capabilities and mobility of electrolyte. A trend-learning algorithm combines the data to provide a dependable state-of-health (SoH) reading in percentage. The system uses battery-specific matrices that are stored in the test device. Figure 1 illustrates a simplified structure of the algorithm.

QuickTest™ structure

Figure 1:
QuickTest™ structure

Multiple variables are fed to the micro controller, “‘fuzzified” and processed by parallel logic. The data is averaged and weighted according to battery application.

US patent 6,778,913

Courtesy of Cadex

As QuickTest™ includes the internal resistance of a battery pack, the welding joints between the cells must be taken into consideration, especially with packs of 10 cells or more. Although seemingly insignificant in terms of added resistance, the mechanical linkage behaves differently to the chemical cell and this causes an unwanted error. The linkage error is not seen on a conventional discharge test or when doing only a resistance check but it interferes with higher end rapid-test methods involving excitation signals that look at many variables.

In addition to the resistance of interlinking cells, each cell in a multi-cell pack responds differently to the excitation signals. As the pack ages, these characteristics begin to diverge; QuickTest™ looks at the average of all cells combined. QuickTest™ only works effectively with nickel-based batteries, Li-ion and lead acid systems uses different rapid-test technologies. (See BU-907: Testing Lithium-based Batteries.)

Last updated 2016-01-22

*** Please Read Regarding Comments ***

Comments are intended for "commenting," an open discussion amongst site visitors. Battery University monitors the comments and understands the importance of expressing perspectives and opinions in a shared forum. However, all communication must be done with the use of appropriate language and the avoidance of spam and discrimination.

If you have a suggestion or would like to report an error, please use the "contact us" form or email us at: BatteryU@cadex.com.  We like to hear from you but we cannot answer all inquiries. We recommend posting your question in the comment sections for the Battery University Group (BUG) to share.

Or Jump To A Different Article

Basics You Should Know
The Battery and You
Batteries as Power Source


On August 17, 2012 at 2:08am
Titan SolarCo wrote:

        You definitely understand how to bring a dilemma to light making it useful. Lots more people need to read this and appreciate this side of the article. You actually have amazing articles. Appreciate it for sharing with us your website.

On March 19, 2013 at 7:04am
Shindinp wrote:

Beautiful and even the best of the best blogs I have had the opportunity to see this is just great for me is Very important, and overflowing to the simple life and living here I was struck nafik.