If you're looking for a simple way to add a battery to your LilyPad project, the LilyPad Coin Cell Battery Holder will do the trick! It's a simple board designed to hold a 20mm coin cell battery and gives you 4 connection points: two positive and two negative, for sewing into your project. Project description, more information and ordering can be found at https://www.sparkfun.com/products/10876