power problem
 

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.

RE: power problem
 

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.

RE: power problem
 

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.

RE: power problem
 

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!

RE: power problem
 

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?

RE: power problem
 

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:D

RE: power problem
 

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..... :D