I'm not too happy with the Spektrum batteries. I had a 3 month old 1100mah pack that had been cycled and showing good, go bad after 15 minutes of flight. I lost a nice plane to a new battery gone bad. What is funny, the voltage showed good but then right after the crash it showed only 4.3 volts. My plane too, went from low idle to full bore, before crashing. I have tried to cycle the battery now and get only 34ma discharge yet it will show 5.4 volts on the meter. I still used JR 7202 and have no problems with JR but I don't think Spektrum is the same. I know of two other pilots who have had the same type of failures with Spektrum batteries. Try for the heck of it, another on board battery. It can't hurt. Do the same test with the new battery. You might have a cell failing or something.