While rechargeable lithium batteries are very popular in the maker community, many projects still call for good old fashioned batteries. AA and AAA batteries are common, but coin cells are also quite useful for compact applications. The CR2032 is king of the coin cell hill, especially for badges. But you can go through quite a few of them during the development process and that cost can add up. This handy device from Peter Misenko (AKA Bobricius) emulates both CR2032 and CR2016 coin cell batteries, so you don't waste batteries.
Misenko's battery emulator should work with any device that has a slide-in style CR2032 or CR2016 coin cell battery holder, as long as it isn't obstructed. Push the emulator into place and plug in a micro USB cable to get clean 3V power. With the emulator plugged in, you can power your badge or any other device indefinitely without needing to worry about batteries dying. Want to measure the current your device is consuming? Simply desolder a jumper and connect the leads from your multimeter.
This device is very clever and based on a single PCB. It only contains a few components: a 3V voltage regulator, a micro USB port, and a couple of resistors. When you receive the board, you snap off the end "coin." It is now ready to use as a CR2016 battery. If your application calls for a CR2032, solder that "coin" on top of the other. The two PCBs stacked on top of each other are equal to the thickness of a CR2032 coin cell. This is a very convenient alternative to a pile of coin cell batteries.