A rechargeable battery (AB) consists of series-connected cells. It is known that even the modern level of automation of industrial production of batteries cannot ensure the complete identity of their electrical characteristics.
The scatter of the actual cells capacity of any electrochemical system within one batch can be from 10 to 20% (Fig. 1-a). During battery operation, the initial spread of parameters increases and leads to a decrease in the operational characteristics of the entire battery. If the actual capacity spread is more than 15%, the “weakest” cell during discharge can go into a deep discharge and even into a polarity reversal (Fig. 1-b, c, d). The service life and battery life are determined not only by the type of cells, but also by the quality of the configuration, i.e. the degree of identity of the cells in the battery.
Figure 1 - Battery cycling with an initial parameters variation of 15%
In order to ensure the high quality of the battery pack and, as a result, to achieve the maximum possible service life, “Research and Technology Centre “ANK” has automated and improved the acquisition technology for both sealed nickel-cadmium cells and cells of other electrochemical systems , including lithium-ion. The equipment developed by the company's specialists allows the selection of cells with any degree of identity of their parameters.
Figure 2 - Test charge-discharge stands
Cycling of up to 48 cells at a time is possible on one test bench. The operator can set various charge and discharge modes and monitor voltage in real time. Using a computer sample, setting the optimal level of the final charging voltage and the permissible spread of the discharge capacity in a given interval of the final discharge voltage, the stand operator receives an automatic selection of suitable cells. The software of the stands visualizes the process and allows to complete the cell also by the method of applying curves.