Integration of Battery Impedance Spectroscopy With Reduced Number of Components Into Battery Management Systems

Abstract

This paper proposes the integration of battery impedance spectroscopy (BIS) into a battery management system with a reduced number of inductor and switch components compared to existing methods. Moreover, this paper presents an internal preheating mechanism, active state of charge (SoC) equalizer, and BIS without an external power source so that there is no additional component needed. During a BIS measurement, the battery management system controls the switches in order to circulate a periodical current signal and measure the battery voltage terminals. The SoC equalizer is needed to equalize the SoC in each battery to prevent over-charging and over-discharging. The internal preheating mechanism is used during low temperatures to preheat the battery since the battery has a higher resistance at low temperatures. The prototype can measure the battery impedance from 100 – 5 kHz with the parameter errors for the internal series resistances of the battery ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_batt</i> ) are 1.59%, 3.72%, and 3.72% and the charge transfer resistances ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R_ct</i> ) are 5.91%, 8.04%, and 6.89% for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B₁</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B₂</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B₃</i> . While the double layer capacitances (C <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dl</sub> ) parameter errors are 5.62%, 7.29%, and 6.48% for <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B₁</i> , <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B₂</i> , and <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B₃</i> . A 50 kHz switching frequency is used with the equalizing duration of approximately 400s with the 90.67% efficiency. The self-heating energy consumption is 0.21 %/° C from 0 to 13.5 °C.