Dear Tom and Ray:
I live near the ocean, and my less-than-a-year-old battery died this week. My neighbor, who jumped the battery with his cables, said that my connections should be disconnected and cleaned with a wire brush due to corrosion. My other neighbor said that she poured a can of Coke on her battery and it cleaned off all of the corrosion. Before I start pouring Coke on my car battery, may I have your opinion on her fantastic remedy? — Martha
Ray: We prefer Dr. Pepper, Martha.
Tom: If you do have a lot of corrosion between the posts and the terminal ends of the battery, it can prevent the battery from being charged completely, or discharged when you need the power.
Ray: But you shouldn't have that kind of corrosion on a year-old battery — even if your next-door neighbors are Mr. and Mrs. Sea Cucumber.
Tom: Corrosion like that usually is caused by "out-gassing," which means the acid in your battery is escaping from its container in gaseous form.
Ray: That can be caused by either a faulty battery — in which case yours should be covered by warranty — or a charging system that's "overcharging" the battery and causing it to emit gas.
Tom: So you'll want to take your car to a good mechanic, and ask him to test your battery and charging system.
Ray: If all's well, the corrosion may be a red herring. Especially since we know herring live near you in the ocean. Your battery may have died due to human error: You may have left a dome light on, or simply left the car sitting for a few weeks without driving it.
Tom: If there is a problem with the charging system, then you need to fix that before you blow through any more good batteries.
Ray: And Coke — with its carbonic and phosphoric acids — will help remove corrosion from battery terminals, as will any carbonated beverage (they all contain carbonic acid). Although a nice sparkling water, without the sugary syrup, would be an even better choice. Add lime or a twist if you want your terminals to feel particularly refreshed.
Tom: Or even better, and cheaper, mix a little baking soda with water to make a runny paste. Remove the battery's terminal ends, smear your mixture on the battery posts and terminals, give them each a little scrub with a wire brush, and rinse it all off with a garden hose.
(Car Talk is a nationally syndicated column by automotive experts (and brothers) Tom and Ray Magliozzi. Write to them at the Car Talk website.)