In my experience, re-inserting the battery connector to the mobo is a pain with the battery in place. There is very little room to maneuver the connector and reconnect it - after several very careful attempts, I got the connector back on, but next time I'm removing the battery.

I just did this - it is kinda tricky. The ribbon cable has a flap on top that is designed solely to help you coax the cable back into the socket....don't make the mistake I did and spend an hour trying to feed this flap through the socket. What worked for me was a combination of using the flap with my fingers and tweezers on the actual cable to reinsert it into the socket. Took a few tries, but I got the cable re-inserted, pressed down on the tiny locking thing, and the keyboard cable was in and secured.

I'd like to add that for me, a 1/16th flathead screwdriver did NOT allow me to remove the tri-wing screws holding the battery in place. After several careful attempts, it became obvious I was perilously close to stripping the screw(s), so I abandoned the attempt to unscrew the tri-wing screws with a flathead screwdriver altogether. As it turned out, I didn't need to remove the battery to do what I needed to do (keyboard replacement), but it would have been a whole lot easier had the battery been easily removable.