How can I keep my battery charged when I don't drive very often?

Dear Car Talk

Dear Car Talk | Jan 01, 1999

Dear Tom and Ray:

My '86 Dodge Aries K wagon has 22,000 miles on it. I park it in the garage year-
round. Because of a disability, I no longer work, so my car sits a lot except for
trips to the doctor and shopping. I have a two-year-old battery. This is my
second one in four years. My problem is the battery goes dead if I don't use the
car every week or week and a half. Should I keep the battery on a charger when
I'm not using it, or is there some other solution to my battery problem? -- Sam

TOM: I suspect the problem is that you don't drive enough to ever really charge
up the battery, Sam. And when a battery is barely charged, and then sits for a
week or two, the voltage can drop below what is necessary to start the engine.

RAY: You may not realize this, but when your car is parked, there are still
things that are draining the battery. There's the clock, the radio presets, the
gas gauge, the computer. ...

TOM: This car doesn't have a computer. It's an '86!

RAY: All right. The abacus.

TOM: Now it's possible that something is actually wrong -- that something else is
draining power, like a glove-box light or trunk light that stays on. So it's
worth asking a mechanic to check for that kind of "parasitic" drain. And ask him
to test the battery, too, just to make sure it's capable of charging fully and
holding its charge.

RAY: Assuming there's nothing obviously wrong, here's what I would do. I'd ask
your mechanic to fully charge the battery and install a "quick disconnect" for
the positive terminal. That's a toggle switch that allows you to easily turn off
the power coming out of the battery. It's very common in marine use. There are
two lines that come off the positive terminal on this car, one that goes to the
starter and the other that powers everything else. That second one is the one you
want to toggle.

TOM: Then, when you know the car is going to sit for a few days or a week, you
can disconnect the positive terminal of the battery and fully protect whatever
charge you have.

RAY: Of course, you'll lose your radio presets. But you'd probably rather spend
15 seconds finding your favorite station than two hours waiting for a jump-start,


Wait! Before you buy a car, make sure you read Tom and Ray's guide, "How to Buy a
Great Used Car: Things Detroit and Tokyo Don't Want You to Know." Send $3 and a
stamped (55 cents), self-addressed, No. 10 envelope to Used Car, PO Box 6420,
Riverton, NJ 08077-6420.

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