Car battery lead can be used, but the hazards are not worth it for the homeowner. You can easily neutralize all the acid from a battery with sodium bicarbonate,which is baking soda. It doesn't overshoot your pH the other direction if you use too much. It is what we used for acid spills while I was on a factory Emergency Response Team (ERT). For a battery, you'll need quite a bit.
The danger is in draining the battery's fluids to another container and neutralizing the interior to make it safe before you open it up. You would drain the battery and fill it with baking soda solution to neutralize the acid in each cell as well as neutralizing what came out of the battery. You'd have to wash out the interior a couple times, and those other reactant crummies will be washing out with your draining of the fluid.
You'd then need to open up the battery by cutting the plastic around the top and lift the lead cells out. I'd immediately dunk them one more time into a neutralizing bath. Once the fumes clear, I'd figure out how to cut the lead free from it's encasement and make manageable chunks for smelting. And there will be a lot of scale on the lead plates. This buildup is It'd probably need some wire brushing to remove as much of that nasty scale as possible before smelting.
Then smelt it for a good long time outside. Once you avoid all the toxic fumes and skim all the crud, you should have plenty of good bullet material. But for all that work it just doesn't seem worth it for the homeowner. But that's how a homeowner could make it happen. It would not be fun in my book. But it is not out of reach with materials you can buy yourself like acid apron, goggles, gloves, respirator, and a face shield for splash protection. Not too mention a container large enough to contain all the fluid and do the work on the battery. Once the acid is neutralized, you could dump it down the drain since it is a water based solution.
Possible, just not very practical.
