Hello, I found the battery that i use to power my DEVO7 ... Walkera F12E JST multi-connector 2200MAH. Sounds like you may need to replace the DEVO7 $AUD119.It may have been fried by the battery that you used.
been there, use sticks to remove thrust k.Enter menu use left up/down to access mode the turn of fixid. Select the right mode as well then the devo7 should work again. There are devo7 videos on youtube.