Turnigy Graphene batteries: calculating the internal resistance

How do you measure the internal resistance of a high performance lipo battery like the Turnigy Graphene series? In this video I show you the theory and practice behind making such measurement.
Using this technique it was determined that with a resting voltage of almost 15V, the 4S 1300mAH 60C Graphene battery has an internal resistance of around 0.0435 ohms (43.5 milliohms)
This significantly better than the 45C Turnigy Nanotech 1300mAH 4S pack which measures 0.056 Ohms (56 milliohms).
Next up will be the 25C Nanotech and the 75C Tatu batteries.
Interestingly, both my Turnigy chargers gave different (and quite a bit lower) internal resistance figures but I suspect these tests are done at a much lower current and internal resistance does tend to vary, depending on the current at which it is measured.