Another good one is the 9v to AAA adapter.
9v batteries are just six AAA batteries in series. They’re smaller diameter so you can print a little sleeve to fatten them up.
They’re also slightly shorter so you can cram a little aluminum foil to meet the contacts.
If you have a lot of 9v leftover from work like I do, and it’s a great tool.
Another good one is the 9v to AAA adapter. 9v batteries are just six AAA batteries in series. They’re smaller diameter so you can print a little sleeve to fatten them up. They’re also slightly shorter so you can cram a little aluminum foil to meet the contacts. If you have a lot of 9v leftover from work like I do, and it’s a great tool.
They’re AAAA cells, not AAA cells, which is why you’re finding they’re too short and narrow.