Operate Droid 4 without the screen

[bbatcher]

I did a teardown of my old Droid 4 to see if I could figure out how to use it without the top half connected. I got it all apart and figured out the top screen and keyboard are only connected by the flex cable. I put the keyboard half back together without connecting the flex cable to the motherboard. It won't come back on. I reconnected the screen and it worked fine. Is there a way to force it to run without the flex cable attached? And if not, can I plug it and make the phone run with the screen turned off to save battery?