Originally Posted by
mattnin
Pablo, the C rating is an ability of the battery to retain its voltage, not capacity, under a high current draw and it is a measure of internal resistance.
Mattin, the following is from Danny/SMC :
"The standard method to test C rate is look at the capacity of the cells at full C rate discharge. Our cells have to remain at 90% of there rated capacity at a full discharge. Some manufacturers use 80% to get there C rate."
According to this it actually is about retaining capacity not voltage. It may be that in general cells with a higher C rating happen to have a lower IR too, but IR may not directly correlate to C rating.
The point I'm really trying to make is that if all we do is look at labels that claim a high C rating we don't always get the best performing battery. Like you have started to do, we need to test them against each other to find out which perform the best.