Hi guys - I have am trying to understand something about my lipo batteries that has given me some headache for a while now. While charging my set of Freefly 6S 9000mAh lipos, I realized the other day that my charger only put about 8000mAh back into a set that I completely emptied (meaning I went down to 3.6V/Cell) - so less than 50% of the total 18,000mAh capacity. That happened with every set, which makes me wonder why I would only use about half the Ah of what I am actually flying around. Long story short, yesterday I flew my copter down to 3.6V/Cell and got a total flight time of roughly 6 minutes. Now a friend of mine had his copter out (same X8 set-up, same electronics, same settings, similar AUW, only difference is that he is using CF props and I am using Xoars). To our surprise he got 11 minutes of flight time with another set of my Freefly 6S lipos. We both ended the flights at 21.6V - now without being under load my set was back up to 22.7V, his at 22.4. The interesting thing is: I was able to add back 10,400mAh in my two batteries, but 15,200mAh in the set that he had used. My question is: how could that be? Why am I reaching the cut-off voltage so much earlier, yet only use 2/3 of the Ah. Whats the average A that should be drawn during a full flight? 50% seems very low. Or differently asked: ( and that brings us to the very basics understanding of batteries) whats the relationship between V and A? Thanks guys!