Cell characterization and modeling of lithium ion batteries

Abstract

The purpose with this thesis was to estimate the parameters from one of the electrical equivalent circuits that are used for batteries. Two different batteries with different chemistries have been tested. First measurements at different frequencies have been performed to obtain the impedance at a specific frequency. When the impedance is known, the information can be used in a Nyquist diagram, where two parameters can be estimated, then the rest of the parameters are calculated from transfer functions. Two methods have been tested to achieve the parameter values. This thesis has tested two batteries at different State of charge and temperatures. The State of charge have been tested from either 0 - 100 % or 100 - 0 % State of charge and the temperatures have been tested between 0° C and 40° C.