[zxcvbob]

It was lead oxide and lead sulfate. You'd have to roast it at very high heat with carbon monoxide (can get that just from mixing in charcoal or wood or oil) to convert it back to lead, and it would stink like the dickens from the sulfur dioxide and probably kill any trees downwind. When you're all done unless it's a really old battery the lead will be contaminated with calcium and who-knows-what. Not much good for bullets but might be good for something.

Here comes the most dangerous part: If you mix calcium-lead with the antimony-lead from wheel weights, the calcium and antimony will bind together and make a bunch of slag. So you skim that off -- and if that slag ever gets wet it gives off a flammable poison gas (stibine.)