I am making a battery tester, lithium ion battery for particular. and I want to measure the internal resistance, but after testing few cells, I am skeptical for my results, since most of them, new or old are around 500-800 mOhm, totally not close to 150 mOhm range as it should be.
The photo: For this instance, the open voltage is 4.18V and load voltage is 3.41V with 1525 mA discharging current; 4.18V-3.41V/1.525A= 0.504 ohm;
Is this the correct way to measure internal resistance? and since new and old cells all have similar result, is it safe to say that internal resistance is irrelevant to health of a li-ion cell?