I have an sjm 400 v2 helicopter with a 30 amp speed control, 4000 mah 3 cell lipo 15c continuous, and a small 3950 kv outrunner motor. When I hover it for about 10 seconds it starts to lose power and I have to land. Then, once I wait for 30 sec. it gets full power again for another short flight. Obviously the battery is fine because I can keep getting the short flights; the battery is brand new and I charge it with the balacer. Could it be the speed control? There is no radio interferance because I have the dx7.

Check the battery under load to make sure it is not droping a cell, if thats not it then its the speed control, one or more of the transistors is bad.

Its not the battery; I am going to buy a speed control. I thought it was the speed control too. It's been through a lot of profile plane crashes befor I switched to helicopters. Everything else on the helicopter is brand new.

What you are describing here sounds very much like a damaged battery. It might not be, but I bet when all is said and done, that's what it turns out to be. I speak from experience here. I had the same exact problem once, and I was SURE it wasn't the batteries (yes batteries - same symptoms with two of them). What did it turn out to be?

You guessed it! Both batteries were bad. I had over-discharged them both once, and that did them in. They would both charge up fine, and deliver full power for about 1 minute, then would quickly fade. I could land for about 30 secs, rinse and repeat 7 or 8 times...


The simplest thing you can do to troubleshoot is try your battery in a 'known good' heli of similar size/specs, and/or try someone else's 'known good' battery in your heli. that way, you can easily narrow it down...

Good luck!

Yes indeed that is why i asked him to test it and not just eleminate the battery cus he THINKS its good ill bet its bad to. But you never know?

Used to have the same problem with my walkera 37, you need a battery with a higher C rating. I would recommend at least 20 if not 25C. You are most likely having voltage dropouts. Also, I would recommend a separate BEC like the sport BEC from Dimension Engineering, or one from castle creations. Only if your servos are a little slow or your ESC runs hot. Happy flying

blade 400, gaui 200, rcu flatout foamy bipe, and a losi speed t for those windy days

That post was over 2 years ago, but his problem for one is he's using way to big of a battery for that size of a heli along with that dinky esc. A 4000 mah 3s lipo is just way to much, and is a very high disc-loading for that heli. He most likely found that out.....