The battery wire is not fixed to the transmitter, it is clipped into small holders that route it around inside. The wire can be removed and the connector unplugged. It is kind of a pain in the butt though.
It might be easier in the long run to cut the wire and solder on a new connector inside the battery compartment.
Or get a peak charger for the field. Throw it on after every few flights and you won't need to carry a spare pack.
Dennis-