Jul 3, 2025 · Explore the significance of battery internal resistance testing, its key methods like EIS and DC discharge, and its role in electric vehicles, backup systems, and battery design.
The battery internal resistance is usually measured in milliohms (mΩ), and measurement methods include AC impedance measurement (EIS), DC voltage drop method, LCR meter test, etc. Ohmic resistance: determined by the electrodes, electrolyte, conductive materials, etc. inside the battery, mainly affecting the instantaneous voltage drop.
There are two methods for measuring internal resistance: the AC method (AC-IR) and the DC method (DC-IR). Testing on production lines uses the AC method, which is introduced by this article.
Although batteries’ internal resistance would ideally be zero, internal resistance exists due to a variety of factors. Internal resistance increases as a battery degrades. On battery cell production lines, defective cells are detected by comparing the internal resistance of tested cells to that of known-good reference cells.
The lithium ion battery internal resistance refers to the resistance of the current flowing through the battery when the battery is working, and indicates the degree of obstruction of a circuit element to the transmission of current. General lithium ion battery internal resistance is divided into AC internal resistance and DC internal resistance.
AC resistance meters apply a constant-current AC signal to the battery. They then detect the minuscule voltage generated by the current and calculate the resistance value. Note that DC resistance meters cannot measure batteries, which have non-zero voltage or electromotive force. Measurement method varies depending on the equipment configuration.
Internal resistance tester The internal resistance tester is used to measure the internal impedance of the battery and the degree of damage of the acidified film of the battery. It is to apply 1KHz AC signal to the tested object, and obtain its internal resistance by measuring its AC pressure drop.
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