modelmechanix

Hi guys, I'm hoping you can point me in the right direction with a problem I'm having.
I bought some new 11.1v 3s2p lipo packs for my MX400 heli.
One of which is not working and for the life of me I can't figure it out.
The pack took a first charge of 1500mah which seems pretty normal considering most packs come more than half charged already.
Charged voltage was a little over 12.4V.
When I went to use it in the heli it powers uo ok and all servo's & gyro etc work but the motor won't spin past 2-300 rpm.
It's like the pack is dead and the lipo saftey cut off is kicking in.
I also though that the pack could be a dud and not able to supply enough amps to run the motor above quarter throttle.
I disengaged the motor to see if it would spin up whilst not under load.
It powers up 100% no problem, weird eh?
When re-engaged the motor with the main gear the same problem occured, basically no throttle at all.

Am I missing something ?
Is there somehting I am supposed to do to new packs?

Any help you guys could offer would be warmly accepted.

Thanks!
Karl

n5iln

Silly question 1: did you balance the pack while you were charging it? Maybe one cell didn't take a charge.

Silly question 2: how did the bird perform with a different pack? That will tell you if it's the pack or not.

modelmechanix

LOL, OK, in answer to silly question 1, no the pack was not balanced as it was charged as I don't have a balance charger.
Maybe that's the problem, one cell didn't take a charge....?
I'll borrow a balance charger tomorrow and balance the pack, hopefully that will solce the problem.

Silly question 2, the bird was perfect with the other pack, spot on.
I can't get my head around it, I have always used my trusty pro-peak constellation charger and it has never let me down.
May be it's time for somehting new.

n5iln

It does sound to me like that one pack is bad. Trot it back to the shop where you acquired it and see if they'll exchange it for you.

rcollector

I bought a cheap lipo directly from china. It turned out to have a bad cell. It acted exactly as you are describing. It seemed like the one cell was just not capable of putting out the amperage it was supposed to.