On my 9.6 volt Tx I fly down to 9.6 and it seems to stay there for a good while. Since it has a voltage display I keep an eye on it. When it drops to 9.5 I charge it (I have accidentally let it get gown to 9.2). My 4.8 volt Rx packs are the same way. I can still get a couple of 10-12 minute flights in at 4.8 reading. Once it gets down to 4.7 the voltage falls off quickly so I charge.