More Batteries

Rechargable lithiums from cell phones are available through surplus electronics catalogs. Be sure to purchase a recharger with them, since lithiums need their own charger to maintain their lifespan. You'll need to solder connectors to the batteries since there aren't battery holders made for them (the phone has its own set of tabs that connect to the contacts in the battery case). I've found three electrical contacts int eh batteries I've nmodified. Two are needed for charging, the third is a control circuit to prevent over charging or over heating.