11.1 Volt Battery pack

This is a battery box that I designed and made for 3.7 Volt batteries. It has a cover and I am using 2-56 size machine screws to attach the lid. The small square holes mark the place to drill for the screws. I used copper sheet and snips to create tabs for the battery contacts. I folded the copper into two layers and it fits snugly in the slot with a tab coming through the recess and making contact with the batteries.