I accidentally charged my battery at over 2 amps (twice actually, don't ask! ), and I think that damaged one cell in the pack. It now runs fine for about three minutes but then drops to ground effect and stays there. I got 7-minute flights up until I (think I) broke it though. Maybe it just needs some deep cycling as I have been lazy with decharging them. I have ordered a 2s1p 1200 Etec Li-Po so I don't worry.