Headlights are a great way to save energy, by taking your light with you rather than turning on room lights. I modified this headlight by punching a small hole in the side, and carefully soldered to the battery end terminals. The wires are run to a two terminal piece of some breakaway .1" on center headers. The solar panels are in series, and a diode is in series on the + lead, to prevent discharge of the cells at night. with 750MHA NIMH AAA batteries, a full day of sun will give several hours of light per evening. The batteries should last for years.