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ELBE, A., NIEDERMAYR, F., ZANDER, D., EGGER, W.
AKKU4FUTURE - MEASUREMENT METHODES FOR STATE INDICATION OF LITHIUM ION ACCUMULATORS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 13
Lithium ion batteries require a strict operation window in terms of terminal voltage, load current and cell temperature. Battery management systems (BMS) have to ensure the safe operation of lithium ion batteries. The functionality of such a BMS features the estimation of the state of the cell in terms and to provide some information (mostly the state of charge) to the user. The state indication is of high importance due to the fact that the knowledge about the health of the battery enables the BMS to act if the battery health gets worse, or even can slow down battery aging processes by acting preventively.
This paper describes measurement strategies to create data for the quantification of the state of charge (SOC) and the state of health (SOH) of a lithium ion battery. A measurement setup has been established to enable automated cycling of the test cells to age the rapidly. During cycling the cell capacity is monitored, because it is representative for the aging of the cell. The measurements are used to fit an equivalent electrical circuit. The derived parameters can be used to estimate the actual state of the cell. The understanding of the cell is the key to be able to design a sufficient and accurate state indication system.
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