I thought that "never store a battery on a concrete floor" thing was an
 urban legend that everyone followed just "in case!"  What is the science
 behind it, and why does Optima claim their spiral cells are immune from it?

 Michael

> 3) Gell-cells are the greatest invention since sliced bread.  They don't
 spill, out-gas (noticeably) or rot your floor.  They are prone to plate
 dammage like a wet-cell though, so never store them on a cement floor.