Testing nickel-based batteries

Nickel-based batteries have unique properties, and Cadex developed a rapid-test method for these battery systems called QuickTest™. The process takes three minutes and uses an inference algorithm. Figure 1 illustrates the general structure of the algorithm applied. 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. Courtesy of Cadex QuickTest™ fuses data from six variables, which 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 stored in battery adapters of a designated battery analyzer (Cadex). The user can create a matrix in the field by scanning two or more batteries on the analyzer’s Learn program. The battery must be at least 20 percent charged. Among other parameters, QuickTest™ relies on the internal resistance of a battery pack, and the welding joints between the cells might cause a problem, especially on packs with 10 cells or more. Although seemingly insignificant in terms of added resistance, mechanical linkages behave differently to a chemical cell and this causes an unwanted error. The linkage error is not seen on a conventional discharge test or when doing a resistance check but interferes with rapid-test methods on voltages above 20V. It is also possible that each cell of a multi-cell pack behaves on its own when excited with a common signal and the result gets muddled.