Originally Posted by btk

Battery Acid is simply sulfuric acid... As far as I know it is not dangerous (other than skin contact in its concentrated form) to use as a pH adjuster in horticulture...

As Quantril pointed out, the byproduct of sulfuric acid and potassium hydroxide is sulphate of potash... I believe this is frequently used compound in gardening from what I can gather with a google search???

Obviously you would not want to use used battery acid, as that would contain lead, but otherwise I believe it is safe.

Someone please correct me if I a wrong.