It's worth adding that the C rating, in terms of the discharge rate, is affected by the internal resistance of the battery -- one only has to imagine (only ONLY imagine this) connecting the two terminals of a LiPo together -- the amount of current will (at least for the first few milliseconds until something melts or ignites) be limited by the "resistance" of the circuit -- in this case, the internal resistance of the battery is all that stands in the way (well, plus the resistance of the wires). Based on some experiments I did, this resistance is typically down in the 25 - 38 milliOhms range -- which is why a LiPo can source such large currents. Heating is controlled by the square of the current as I recall my physics. Power = Volts x Volts / Resistance, I think. But don't forget -- in a system with X units each having a probability, p, of failure, the larger X is, then the larger p becomes. Ask any pilot with a twin engine rating! The probabilities work like this: A dual battery setup: 1. Is twice as likely to develop problems with either battery. 2. Is four times less likely to develop problems with both batteries. The kicker is that, the way the dual batteries are wired up, item 2. never gets to apply -- because if one battery fails, I suspect it is going to drag the other one down with it. So all you're left with is, with a dual battery, it's twice as likely to fail than a single battery. So in Dirty Harry's universe, the phrase is: "D'ya feel lucky today, Copter Pilot....?" What we really need to make dual batteries safer is an isolating circuit so that, when one battery fails, it is isolated from the second battery. Andy.