There's a reason why standard batteries contain warnings for you NOT to attempt to recharge them. But, if you're either brave or cheap, here's a guide to extend regular batteries by around three charges with 50 cents of parts from The Shack.
Glossing over the details—we fell asleep during just about all of our EE classes in college—you do run the risk of dripping weak acid on your hands. Or worse. And by worse, we mean possibly exploding a battery in your face. Not our idea of fun, unless you're trying to hit on that cute nurse in the ER. Hey baby, is that shrapnel in my eye or did you get a new haircut?