Step 10: The battery compartment
There is a really easy way to cut acrylic material. You just cut into one side with a sharp knife and than you break it in a vise or on the edge of a table.
For the battery-compartment we need to small pieces on the sides and a big piece with a hole for the battery in it, in the middle. I first cut off a small strip for the sides. When I put it inside the aluminum profile, I can see exactly how long it should be and cut it there also. I need two pieces like that.
The piece in the middle should fit exactly in between the two small pieces en must be bigger than the size of the battery.
When you put the two small pieces inside the bottom-U-profile where they should come, it is easy to see trough the clear acrylic where the holes should come.
Drill this holes with a 3 mm sharp-steel-drillbit and don't push to hard or the material might break. Remove the drilled material from the drill bit often. It might be molten onto the drill, but it should be easy to remove.
In the big piece we need to drill a big hole, the size of the battery (20 mm in my case). I had a nice drill for that. Still I had to go slow and removed the scrapings very often.
To cover the battery, I used a thin sheet of plastic. With a small screwdriver I pierced four holes for the bolts and one more for the positive lead to go trough. This fifth hole must be next to the PCB and next to the battery.