Car batteries do their duty sitting on a metal shelf in your car. But when car batteries die, and you take them to be diagnosed, mechanics always set them on a block of wood. For them, the long-standing rule is that you should never put car batteries on a concrete floor, unless you put that block of wood down, first. If you should forget, or don’t “know” better, and place the battery on the floor, you will be admonished by your mechanic, who believes concrete flooring is implicated in draining car batteries. This concept, however, is a complete myth: an absolutely silly idea.

Car batteries, for at least fifty years, have been encased in hard plastic, eliminating the possibility of grounding out. Before then, batteries were covered with rubber or wooden cases, which in theory, could have leaked battery acid onto concrete floors, thus creating a path to ground. But surely it’s been long enough since these cases went out of production that we can stop insisting it’s still an issue?

Insulation from the Cold?

On the other hand, some say the block of wood isn’t about conducting electricity from batteries to the ground, but only about conducting heat. The wooden block, according to this theory, has insulating properties. But this explanation ignores the fact that the hard plastic casing encasing car batteries, also has insulating properties. At any rate, the theory stems from the idea that batteries discharge faster in colder temperatures. This too, matters little: the battery should work the same as it did before once it warms up. The truth is that cold temperatures increase battery life, while warmer temperatures increase self-discharge rates, actually decreasing battery life.

Still others argue that it’s not about going cold that makes the battery die, but a difference in temperature between the top and bottom of the battery, which might result in damage to the plates. That this would occur seems unlikely unless you have hot air blowing just over the top of your car battery, as it sits, sans wooden block, on a cold concrete floor.

Car Batteries Leak Only Very Rarely

The fourth theory floated about is that the wooden block is not about protecting the battery, but about protecting the floor. This makes the most sense of all the theories that abound in regard to setting car batteries on wooden blocks. Batteries leak sometimes, and acid isn’t kind to concrete (or any other) flooring. But this is so rare an occurrence in an auto shop or home garage as to be implausible. Car batteries generally do not leak under normal conditions.

In short, if you serve as your own mechanic, you can lose the wooden block. Just don’t let anyone see you setting that battery down on the ground. Unless you want a lecture from those who don’t know any better. The myth, it seems, is stronger than the facts.