No, you can't. The P2 battery has a balance charger built in to it. It just needs +12.6V in and it takes care of the charging process.
If the AC Adapter for the Accucel supplies 12.6V, then you can jury-rig that to the Phantom battery to charge it. Just get the polarity right!
(Look at the color of the wires inside the battery bay to figure out the battery polarity.)