Dear Tom and Ray:

I am a middle school science teacher who is questioning a time-honored warning handed down to me from my grandfather. My wife and I were cleaning the garage when I was shocked to see a car battery resting on the concrete floor and not resting on wood. Pat, my wife, said, "What difference does it make?" My response was that the cement would drain the battery. Luckily for me, she didn't ask how, because I would have been stumped. Can the cement drain the battery, and if so, how? -- Dave

Tom: Well, Dave, you're a model for middle school science teachers everywhere. Why? Because you didn't try to fumble around and make up an answer like I would have!

Ray: You can completely ignore your grandfather's warning these days, Dave. In his day -- even in your father's day -- 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 (which we've been using exclusively since about the time Nixon said, "I am not a crook"). That's because molded polypropylene (a k a plastic), as you probably teach your students, Dave, is not porous at all.

Ray: And here's the interesting thing, Dave. 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 LONGER than leaving it on a wooden pallet! How do you like them apples? Copyright (c) 1999 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

Changing your oil regularly is the cheapest insurance you can buy for your car, but how often should you change it? Find out by ordering Tom and Ray's pamphlet "Ten Ways You May Be Ruining Your Car Without Even Knowing It!" To order, send (check or money order) to Ruin, P.O. Box 536475, Orlando, FL 32853-6475. You can also order online.

© 1999 by Tom and Ray Magliozzi and Doug Berman Distributed by King Features Syndicate, Inc.

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