Agreed, if it's been shelved for awhile, then it should be checked.
The battery only has 2 cells, becase 1 lipo cell has a nominal voltage of 3.7, fully charged a 4.2. So 2 cells is 7.4 nominal/8.4 charged, unlik 1.2/1.45 volts per celll on a nimh. Personnaly, I recommend a eneloop pack for you transmitter. It is a low self discharge cell, will last long, so the only real advantage that the lipo has is weight, but it's only a transmitter. I don't like lipos in my transmitter, but that's just me.
These guys have a pre soldered eneloop pack designed for a dx7s:
http://www.batteriesamerica.com/newpage8.htm
Hubert