There are No screws holding the case together. The three contacts that appear to be screws are not holding the case. They are battery charge contacts only.
The case halves are bonded together by either glue or ultrasonic welding.
I use either a x-acto knife or scalpo to cut the seams apart. I have also used a "hot knife" but desided the x-acto or scalpo worked best. Easier to control.
After replacing the batteries, I use a UV cured bonding agent to reassemble the case.
You have to take your time when separating the case. That is if you want a usable battery pack after you're done. Above all, do not rush the project, it will take some time to do a proper job.
Anyway, good luck and ha e fun.
Clyde KC7BJE
Retired Electronics Manufacturing Engineer
?
Clyde Lambert