Many persons have the thought that when batteries sit on concrete, energy "leaks out" or they are ruined. The answer is that letting modern batteries sit on concrete doesn’t harm or discharge them in any way.
Though, this legend is historically based in fact. The first lead-acid batteries were made up of glass cells that were enclosed in tar-lined wooden boxes. A damp concrete floor might cause the wood to swell, breaking the glass inside.
The Edison cell (for instance the nickel-iron battery) that preceded the rubber-cased battery was encased in steel. Those that were not isolated in crates would discharge into concrete quite easily. Newer battery cases used primitive hardened rubber, which was somewhat porous and might contain lots of carbon.
A moist concrete floor joined with the carbon in the battery cases might create electrical current between the cells, discharging them.
None of this is a dilemma with modern batteries — safe in their hard plastic shells. In fact, concrete is normally an excellent surface on which to place a battery bank.
The electrolyte in a battery resting on an extremely cold floor with very hot air around it might stratify, causing damage from sulfation; while concrete provides good thermal mass to buffer any temporarily extreme temperatures in the battery compartment.
Car batteries are full of toxic chemicals and have to be dealt with specially when they die. The green thing to do is to squeeze as much life out of them as possible and decrease the overall amount of batteries that you are going to need in your lifetime. Here are some 6 great car battery maintenance tips from Auto.howstuffworks.com.