RE: JR 12X Battery problem
You should open the transmitter battery door and make sure that the lead is connecting properly to the battery itself the hole in the battery door for the charge lead adds depth to how far the lead has to go in to make a connection. also, you said that you tried multiple chargers, but did you use the same lead with all of them? maybe there is a bad connection in the lead somewhere. Try a different lead, or try plugging the battery into the wall-wart charger that came with the system and see if the little red light comes on.
I would also check to see if you have the correct polarity on your lead. (remember, center is black on JR)
ror, the 10X and 12X radios have the charging plug integrated into the battery pack. Thus the charge plug connects directly to the battery pack, NOT the radio. therefore there cannot be anything the radio is doing to prevent charging the pack, although I've never tried charging the battery with my 10X on to see if it would work. This setup allows the battery to be charged with the standard charge plug even if the battery is removed from the Tx.