3AA to D cell both alkaline and rechargeable batteries v8

thingiverse

So you'll need a couple D cells. This will use three AAs in parallel, so the power output should be close to that of a single D cell. I like using one button brass fastener on top with tin foil folded over it to connect all three AAs. And three button brass fasteners on the bottom without tin foil - the three fasteners are bent to connect all three AAs. There are three fasteners on the bottom so that the adapter will work with any type of spring. Check out the extra bend in the fasteners on the bottom that would normally stick out the side of this thing. By bending inward, the battery end fits more easily onto the adapter. The slot for each AA is 15mm wide, so a rechargeable can fit just as well as regular alkaline batteries.