Even the bullet casters, who will scrounge lead where ever they can find it, don't mess with batteries. Lots of bad things can happen especially if you try to melt the lead to clean it up. Here is post from the cast boolits site.
"The warnings about smelting automotive batteries to recover the lead they contain needs a bit of explanation. Doing so really does have the potential to harm or even kill you and here is why. Maintenance free/low maintenance batteries use calcium metal-doped lead to catalyze the hydrogen gas generated from water electrolysis back into water. That is what makes the batteries low maintenance or maintenance free, you don't need to add water to the cells as often like in the old days. When the battery lead is melted down there is enough sulfuric acid from residual electrolyte trapped in the lead dioxide and lead framework of the battery plates to react with the small amount of calcium metal in the lead alloy. Normally when sulfuric acid (or water) gets in contact with calcium metal it undergoes a rather vigorous reaction that generates hydrogen gas. In and of itself this is no big deal, hydrogen is a simple non-toxic asphyxiant that is also flammable. But the lead alloy used in batteries also contains a bit of antimony and even arsenic to help harden and strengthen the lead to withstand the vibration and general knocking-about batteries have to withstand in order to survive normal automotive use. When hydrogen comes in contact with arsenic and antimony, or compounds of these two elements, the hydrogen reacts to form ammonia analogues called arsine and stibine, AsH3 and SbH3. Both of these are heavy gases and both have the similar characteristic odors of rotting fish. In World War One the Germans experimented with these, along with phosphine, another rotting-fish-smelling gaseous ammonia analogue with formula PH3, as war gases. As such they were highly effective since they are deadly in amounts too small to easily detect. In even smaller amounts that are too small to immediately kill they cause rather painful lung damage that often eventually leads to emphysema and lung cancer.
So, leave smelting car batteries or using lead smelted from them to professional recyclers. Many folks including myself have successfully smelted batteries and lived to tell about it, but the risk is just too great to mess with the stuff." The link is here
Why Car Batteries Are Dangerous - Cast Boolits
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