AC internal resistance

It is also possible to measure the AC internal resistance for a given frequency. 

For a portable secondary battery, the standard EN 61960 [2004], on secondary lithium cells and batteries for portable applieations, proposes to determine the AC resistance by applying a sinusoidal voltage at a 1 kHz frequency, of less than 20 mV peak value for 1-5 seconds and measuring the current. The resistance is then the ratio of this imposed efTective voltage to the measured effective current. Thus, in reality, it is a measurement of the modulus of the impedance. 

37IEC 61982-3 or EN 61982-3 (April 2002) Secondary batteries for the propulsion of electric road vehicles - Part 3 performance and life testing (traffic compatible, urban use vehicles). 

38 The standard speaks of alternating current resistance, whereas electrotechnicians know that this relation gives the modulus of the impedance. 

We can go further still and measure the complex impedance (comprising both the real and imaginary parts) presented by a battery (or an electrode in relation to a reference electrode) on the basis of the frequency. This characteristic measurement uses the technique of electrochemical impedance spectroscopy This consists of applying a sinusoidal disturbance 

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