As you can see in the video titled electric engine sputtering, my electric engine sputters when I apply full throttle? 1800mah/20c lipo battery & 35 amp esc. It seems to do it with both batteries, even at full charge. One is worse than the other. If you watch the video titled 5th flight, it didn't do it at all? Any suggestions would be appreciated. Thanks in advance.
Brac
[link]http://www.youtube.com/brac1960[/link]

It's not sputtering. The ESC is telling you that the battery is getting close to low voltage cutoff.

Either the batteries are discharged, going bad, or you're drawing too many Amps from them.

My suspicion is the last of the three. Too many Amps. If it were the batteries running out of charge or going bad, you wouldn't have been able to fly that long.

Is this a stock power system, a 20C 1800 should fly a stock Trojan fine.

Since you say one battery is worse than the other I would suspect they have both served their usefull life.

Thanks guys.
These batteries are actually from my helicopter, but the stock batteries for the plane are supposed to be 1800/20c also, but they did have a recommended upgrade to 2200 mah. It did not do this when I first got the plane and I was getting a good 9 minutes of flight time with no issues. That was my suspicion also that the batteries are done, I have probably flown with them and charged them about fifty times. I will get some new batteries and try them.
Thanks guys