Is it still true that you shouldn't put a car battery on the concrete floor of a garage?

Dear Car Talk

Dear Car Talk | Apr 01, 1996

Dear Tom and Ray:

My wife drives 15 minutes to work five days a week. After a recent vacation when she didn't drive the car for a few weeks, I found the battery dead. I took the battery out and trotted up to the local service station, which shall remain nameless. I say this because the man wearing the star took my battery, put it on the bare, concrete floor where the charger was, and connected the charging cables.
A heated discussion proceeded between the two of us about the lack of a piece of wood for insulation between the battery and the floor. I have taken enough mechanic classes in my life now to remember being cautioned to never place a battery that you wanted to use again on the ground. Be it dirt or concrete, the battery's life would be shortened. Being told that it had something to do with the earth's mass being negatively charged was always enough for me to accept this rule of thumb. BUT, the star man told me I was a fool for believing this absurd and unproven concept.
What is your learned opinion? I'm on the verge of losing sleep over this issue. -- Ballan

TOM: I actually see two issues we need to address, Ballan. One is why it's OK to leave a car battery on a concrete floor, and the other is how you're going to apologize to this gas-station mechanic whose mother you probably insulted during this argument.
RAY: While there used to be some basis for not leaving a battery on the floor, it doesn't really apply anymore.
TOM: If the outside of a battery is covered with acid -- on the sides and the bottom -- then the moisture in the concrete (or in moist dirt, I suppose) could serve as a conductor, and could increase the rate at which the battery drains.
RAY: But even at that, you wouldn't expect to see any real change in the battery's effectiveness for many weeks.
TOM: Moreover, you just don't see batteries covered in acid these days because most batteries are maintenance-free, and they're sealed up pretty tight.
RAY: The only way you could make that kind of mess on a maintenance-free battery would be to severely overcharge it and make the acid bubble over onto the casing.
TOM: So this "rule" about leaving batteries on the floor made a small amount of sense before maintenance-free batteries, but it hardly applies anymore. In fact, a battery manufacturer near us says that during the summer, they store their new batteries on the concrete floor because it keeps them cooler, and therefore helps them PRESERVE their charge.
RAY: Now let's address the second issue: how you're going to prevent this guy at the local gas station from pouring Mountain Dew in your gas tank next time you come in. We know you told him in no uncertain terms what a stupid moron he is, and now, you need an elegant way to back down.
TOM: Here's what you do. Tell him you didn't want the battery on the floor because you were afraid he might trip over it and hurt himself, and you were only looking out for his best interests. Good luck, Ballan.

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