Long story short, I needed to source about 20lb of lead cheaply and decided to take apart an old car-sized marine battery a friend gave me.
If you ever do that (and my advice don’t) just get the contact points and the big chunks that bridge the plates. You can see the latter on the picture inside the battery case.
Getting the lead mesh from the plates is not worth the efforts. There is more junk there than lead.
Baking soda and/or pool’s PH+ chemicals can be used to neutralize it. Borax can be used too. It converts it into boric acid and anhydrous sodium sulfate (neither of which is a nasty stuff, apparently). The process is simple. First, the water is added to dilute the acid (it’s not pure, so 50/50 mix is good enough). Then the neutralizing agent is added slowly (if doing it start with one spoon to see how it reacts). The baking soda and HTH PH+ bubble when added (borax doesn’t). As soon as it stops bubbling when the baking soda or HTH PH+ is added it should be good to dispose of.
It took quite a bit of the stuff to neutralize all the acid in the bucket and its remains in the battery case. I have scavenged and dumped in a pound or two all the above chemicals till it finally stopped bubbling.
The final result: 10lb
And after smelting there were only about 6lb left.
The conclusion: a lot of time, efforts and baking soda wasted (borax and PH+ did not count, didn’t need them anyway).