On a standard car battery at the time of manufacture the negative plates are filled with lead oxide which is known as “red lead” and the negative plates are filled with lead dioxide also known as “spongy” lead. Basically the active materials absorbs sulfate from the acid during discharge and give up the sulfate while the battery is being recharged.
Although the lead can be recovered from car batteries... it is a more complicated process than simply taking them apart and melting them down. This is too bad because I have dozens of old car batteries and I cast my own bullets. So don't think that I haven't thought of it. If you know of plans for a simple way to recover the lead I would love to give it a try. ; )
Not quite. The positive side is lead dioxide a/k/a "red lead". The negative side is "spongy lead," which is just finely divided lead metal. Discharge converts lead dioxide to lead(II) ions, acid to water, and lead metal to lead(II) ions. The lead(II) precipitates out as lead sulfate.
Charging does the reverse.
I've read that it's near impossible to make bullets from battery lead, because the acid is impossible to remove completely. The only thing battery lead is good for is to make new batteries.