It’s a project called snapVCC, and it turns a 9 volt battery into a regulated 3.3 or 5 volt supply. The idea behind snapVCC is simple enough; just add a circuit board to the top of a nine volt ...

button cell and 9-volt batteries, as well as hearing aid and watch batteries. Lithium-ion batteries (found in smartphones, smartwatches, laptops, tablets and power tools) should never be recycled ...