It’s a hassle having to look through various drawers to find a battery that’s in the size you need. It’s even a larger hassle if you have a bunch of batteries but can’t find one in the size you need. Panasonic’s emergency flashlight took that into consideration by allowing people to use it with batteries in various sizes.
For everything else, there’s the Battery.Family.
It’s basically four 1.5-volt batteries housed in one huge size D battery. With each ‘family’, you get a size C, size AA, and size AAA battery aside from the D-sized one. The AAA actually contains the power source, while each of the larger casings just contain the contacts to fit the appropriately-sized battery. It’s like those Russian Matryoshka stacking dolls, but in battery form.
Battery.Family was designed by Soohwan Kim, Junho Yoon, Dohoon Lee and Hyojin Park and it is, unfortunately, just a concept design for now. But here’s to hoping.