Slide the internal part back into the handle casing. You might need to apply a little force to get it to click in all the way. Replace the small trape...
This will show you how to replace the internal battery on your Sonicare Elite 7300. After having my 2nd one die on me within 3 yrs I figured out how to rip it apart and fix it.
Step 1: Disassembly
The first part of disassembling the elite 7300 is removing the small trapezoidal rubber bumper at the top back of the unit. This piece has two small clips which holds the internal components inside of the casing. Next, slide the main screw ring (upper left) off of a brush head. Twist the screw ring down onto the handle all the way and pull the internal components straight out.