AC Impedance ohms are not necessarily 1:1 correlation to DC IR resistance ohms.I wasn't suggesting an alternative method for testing IR; I was suggesting a potential method to see what the accuracy/precision/whatever of the PL8 IR measurements might be. I was suggesting that the PL8 has to use the cell ports and circuitry to measure the voltage response of the cells - so the IR measurements are probably limited to how good those are - and that the specs for cell balancing likely reveal that 'how good'... If the device can only balance to say plus or minus 0.003V or something like that, then that's likely the precision or whatever of the IR measurements...
I also don't know if the correlation is linear, or consistent.
AC impedance Ohms vary with frequency , shape of the conductor , nearby magnetic or electrical sources , etc.
Heck .. Aluminum windings in a transformer give a different AC impedance ohms than copper windings .. even if the two windings have the same DC IR resistance ohms.
We also don't know the software algorithm used by the PL8 as it changes the AC frequency , as the voltage changes, as the amps change , etc.
Although I agree a correlation data set / graph , with reasonable tolerance , could be made from doing a variety of tests .. I just think it would require more than just the 3 aspects of measurement of DC voltage for the PL8 .. it' accuracy , precision, and resolution.