Paxar TC6037EM - Manual (Page 11)

Using Batteries 2-5
Backup
Battery
3. Remove the backup battery by turning it slightly counterclockwise,
and pulling it out.
4. At the same angle, place the new battery (positive side facing away
from the main battery) at the edge of the track and under the spring
contact. As you push it in, it will straighten itself. Make sure that the
battery lays flat.
5. Immediately replace a fully charged main battery.
6. Slide the compartment door shut. You will have to press the main
battery in slightly so the door fits over it. When the door shuts, you
hear it click into place.
7. Turn the printer on and wait for it to completely initialize.
8. Turn the printer off again.
The last two steps will help avoid reducing the coin cell life.