Well there probably aren't any metals that you can find cheap or free that you would be able to use to fabricate a dry battery of the type you have in mind that won't involve some pretty hazardous reactions. If you find any, I'll be the first to admit the error of my ways. For example, Lithium is all the rage in batteries, but trust me you don't want to touch metalic Lithium, not even with sombody else's hands. Be careful and stay safe.

I appreciate the concern and the advice. Actually I came home from work yesterday and put together a dry cell battery quite quickly without dangerous materials and after drying for over a day it is giving off a voltage of 0.73 consistently no matter what I do with it. Now this thing is about the size of two or three quarters stacked on top of one another. As a matter of fact it even acts like a capacitor in the sense that when I apply a voltage or heat to it the thing charges. However the initial charge dissipates without any components (so far) in place to block the backfeed. But it only discharges to the 0.73V range and stays there constantly. I find that quite interesting and I'm still alive!

 

That's really good to know.