Fact or fiction: It's OK to set your battery down on a concrete garage floor.

Dear Car Talk

Dear Car Talk | Nov 01, 1999

Dear Tom and Ray:

This business of batteries and concrete floors needs to be explained and put to rest. Years ago, everybody knew that you were never supposed to put a car battery on a
concrete floor because it would be quickly ruined. That statement was absolutely true, but they weren't talking about the BATTERY being ruined, they were talking

Batteries used to be "topped off" with water, which resulted in acid being spattered about. If you put one on a concrete floor without carefully washing it, the acid ate
into the concrete, quickly ruining the floor. It didn't hurt the battery one bit, but people who misunderstood the advice and wanted to appear knowledgeable came up
with all sorts of foolish explanations as to why the battery should be ruined. Even an acid-spattered battery will not leak its charge into the earth. There may be leakage
across the terminals of a "top-post" battery, but that would be slight.

So here's the story: If a battery is clean, you can safely put it on your concrete floor. If it's acid-spattered, put it on somebody else's concrete floor or stick a board under
it. -- Clay

RAY: Clay, you sound so utterly convincing. If it were up to me, I'd buy your story lock, stock and barrel. But my brother says you're full of baloney.

TOM: The GFCA (Garage Floor Cleaners of America) may indeed have had a hand in keeping batteries off concrete floors. But the real concern WAS the batteries.

RAY: Thirty years ago or so, most battery casings were made of hard rubber. And because of the porosity of that material, battery acid would sometimes seep through
the rubber and create a conductive path through the damp concrete, draining the battery.

TOM: But that can't happen today with plastic-cased batteries. That's because molded polypropylene (a k a plastic), is not porous at all.

RAY: So today, you can put your battery on a concrete floor for as long as you want. And here's the interesting thing, Clay. The cooler the temperature, the slower a
battery's rate of discharge. And because concrete is often cooler than its surroundings, leaving a modern battery on a concrete floor might actually make it last

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