Obviously the advice given about the lead pollution is sound, however, the whole of our garden (just under an acre) was full of batteries, though not car ones. Our batteries range in age from the Accumulator types of the early part of the 1900,s up to modern torch batteries. We still find the central core of these (the carbon rod) and the carbon squares of the older types. We put our Veg growing area in the place where we found the least number of them. Been growing fruit and Veg here for the last 18 years and eating it and we ain't dead yet.
So unless the soil is really contaminated there should not be a problem, especially if the batteries were intact, not broekn into pieces.
Hope you manage to find out what has happened, for your own peace of mind.