Dell Inspiron 27 7720 All-in-One Owner's Manual page 70

Figure 44. Installing the coin-cell battery
Steps
With the positive-side facing up, insert the coin-cell battery into the battery socket on the system board and snap the battery
into place.
Next steps
1. Install the system-board
2. Install the I/O cover.
3. Install the back cover.
4. Install the stand.
5. Follow the procedure in
70 Removing and installing Customer Replaceable Units (CRUs)
shield.
After working inside your computer.