Li-ion Polymer Battery and measurement of internal resistance

[Kiriakos GR]

Li-ion Polymer Battery and or Pouch Battery Cell, this has several little secrets.

Regarding an accurate internal resistance testing, we should know a few details. 
For Li-ion Polymer Battery this including basic PCM module,  you should expect 80 mOhm, as internal resistance of the PCM alone.

Examples:
3.7V / ≤ 40mΩ for Cell 
3.7V / ≤ 120mΩ for Pack  ( + PCM)

7.4V/ Two cells  =  ≤ 80mΩ for Cell's   
7.4V/ Two cells  =  ≤ 160mΩ for Pack  ( + PCM)

Such details matter allot, when comparing battery datasheets due a different brand or factory.
Not every one will list both specifications = Cell or Pack+ PCM

When inspecting an used Li-ion Polymer Battery  3.7V ( this including a Power Control Module), an approximate of 80 mOhm this it should be removed from the measurement. 
At Li-ion Polymer Battery, for having an accurate evaluation, you need to discover the actual product (brand or factory) datasheet.

Never compare due a similar model datasheet, because small size battery makers, they use lots of manual labor and not fully automated production lines.
Anything produced due automated production lines, this has more consistent electrical parameters, along dimensions and weight.