[zxcvbob]

Car batteries really don't have much lead; they have a lot of lead oxide and sulfate. I think in an emergency I could smelt them down (drain and burn them in the rubber or plastic casings with a lot of charcoal) but it wouldn't be pretty, and it would not be very good lead. It's alloyed with calcium. And maybe more exotic metals now like stronium.

I don't remember the details, but if you mix calcium lead and antimony (or arsenic) lead, you get a lot of "cottage cheese" dross that if it gets wet gives off extremely poisonous gas. Zinc and antimony might do the same thing, I don't know.

If you have lead that's contaminated with zinc, you can't really just dilute it with good lead because a little zinc ruins a lot of lead. You might can use it up by adding just a little to a whole pot of lead. (it might even be a good hardener in small enough amounts, but that would be tiny amounts.