You're in total green-mixed-with-frugal mode right now. It's all about double duty: saving money and helping the environment. And you're clever enough to marry the two. Contact your local hospital and ask about batteries. Many health care centers send patients home overnight with vital-sign monitors, and after just one use, those practically new alkalines end up in the trash. It doesn't hurt to ask: you could end up with a never-ending supply of free batteries.