For GEMMA projects in particular, a slim battery holder with a built-in power switch is handy. Coin cells are fairly high capacity for the size; this pack can give you about 6V and 250mAh. However, it can’t provide tons of current for long periods of time, this pack can power a gemma plus three or four neopixels for a couple hours-- pack spares in case the party runs long.
Projects you can make using this battery pack:
