Stick it on a 12 volt field charger (it must be a dumb charger, at least one that doesn't care if the battery voltage is too low for the type of battery) for about 15 minutes to a 1/2 hour or until it gets back to the minimum voltage that your balance charger doesn't reject it for too low voltage. If it has had it, nothing to lose. I've done this a couple of times now, pushing my luck though. One of my batteries has puffed up every so slightly and I keep a very close eye on it now.
It took 2800 odd mA according to my charger so I'll use it and see how it goes. It didn't get warm or puff or anything so I might be lucky.
Ended up that I didn't sort the yawing problem. Went and flew it again and it was still doing it BUT I figured it out I think. I was checking out the slider output screen and noticed the yaw was doing some weird stuff so I checked the transmitter - you guessed it, weird stuff too!
Recalibrated the sticks and pots but still no good. When I move the throttle from 0 to full with no rudder input, the output from the transmitter actually goes from left rudder diagonally up to the centre and then from the centre to full throttle it jumps around randomly and ends up diagonally to left rudder again.
So I guess that means a new gimble coming from china for me
. I know it's a cheap transmitter but pretty crap really. At least it's only about $7 because I won't get warranty due to reflashing it.
So hopefully that will sort it out. I'll post a video of what it's doing if I can figure out how.