[Jay Kickliter] built his own coin cell battery recharger. This won’t work on the vast majority of coin cells as they are manufactured as disposable parts. But there are rechargeable options … ...

(Other brands are available for about $15 for two — but they'll need a D-cell charger, which adds to the cost.) ... The spacers come in two sizes to make a AA into a C- or D-cell battery.

A AA rechargeable battery, center, can take the place of D cells or C cells by slipping into sleeves (D size at left; C size, right) designed to hold the AA battery in place.

Rechargeable coin cell batteries are great for all your small projects. They look exactly like regular coin-cell batteries, but in a shocking turn of events you can recharge these little guys. They… ...