ORIGINAL: carrellh
If I remember correctly, the 'student' battery has to be somewhat charged if you're using a mixture of Hitec and Futaba transmitters and are using the Hitec one way trainer cord.
When I started flying we had a Flash 5 master and 6XAS student and I think my battery had to be charged (or at least not be totally dead).
No, you do not have to have a battery in the buddy box but you must use the Hitec trainer cord if mixing Hitec and Futaba and then make sure the cord is plugged in correctly - trainer end on buddy box, master on the other end.