====== cells ======

===== internal resistance =====

All you need is a 4 ohm 5W power resistor or similar and a multimeter.

  * First, measure the battery's voltage when charged. This is V1
  * Next, connect your multimeter leads to each side of the resistor and briefly connect the resistor across the battery. Note the voltage reading, this is V2.
  * Measure your resistor to get its precise resistance, this is R

The battery's internal resistance (Ri) is calculated with the formula:


Ri = (V1-V2)*R/V2


18650 Ri values:
  * 75-150 mOhm - Excellent
  * 150-250 mOhm - Good
  * 250-350 mOhm - Marginal
  * 350-Up mOhm - Bad