Application notes 21 min read

Dynamic resistance determination. A relation between AC and DC measurements? – EIS – Battery- AN 38

Latest updated: August 31, 2021

Abstract

In this application note we demonstrate how to determine the dynamic resistance on a LiFePO4 battery using a DC technique (GCPL5), and those results compared with that of an impedance spectroscopy technique (PEIS). The conclusion of this comparison is that the dynamic resistance can be used as a rough approximation of the impedance data determined by EIS and that a wide frequency range EIS is still best to fully characterize a battery.

 

Introduction

Currently, several types of batteries are investigated (Li-ion, LiFePO4, ….). Each type has its own specifications such as nominal voltage (V), capacity (Ah), power (W), energy
(Wh), cyclability… The apparent resistance RΔt of the battery is also a relevant parameter. This resistance can be determined by a simple current interrupt technique. In this technique,
a current pulse is applied to the battery and the voltage shift is measured after a certain period of time Δt (Fig. 1). The ratio of the voltage shift ΔE and the current difference ΔI yields to a resistance, R:

 

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