ORIGINAL: Spockie-Tech
To check your electrical system properly, you need a voltage/multi-meter so you can measure the voltage under load..
Like I said, weigh down the choppers skids with something, hook a meter to the battery connector (use some bits of thin wire to poke down the back of the black plastic connector on the heli side where the terminals are reachable).
Sit the meter back out of the way, make sure the wires arent going to get sucked into the rotor wash, wind her up and watch the battery voltage as you bring up the blade pitch.
a charged 10-cell NiCd/NimH pack should have around 12-13 volts on it at no load. Once you load it up, it shouldnt drop any lower than about 11v.. maybe 10v if its working *really* hard, but if it gets that low, its struggling and wont last long
If it goes below that, its either not charged properly (what are you using to charge the pack ?), or its stuffed and cant handle the current load.
Once you have verified that your battery is coping, *then* you can go looking for other possible causes..
I just gotta thank you for this post, as I couldnt figure out why my #36 wouldnt get off the ground, despite my efforts to balance and trim everything up properly. Whenever I tested my stock 650mAh 12v battery with a multimeter it measured 14v on a full charge, I even took it to a hobby shop and they tested the same with their higher quality digital multimeter. Then after reading this post I decided to test the battery under load. Well what a disaster, even at quarter throttle the voltage drops below 10v, I said "****" to myself and then just gave it full stick, at this point the tail servo stops responding (no wonder!) and the voltage dropped to below 8v, probably around 6v or 7v. So the problem isnt the motor itself but a ****ty battery.