To use or not to use the headlights...

Dear Car Talk

Dear Car Talk | May 01, 1991

Dear Tom and Ray:

Does driving a vehicle with the headlights on appreciably shorten the life of the battery and/or alternator. I am asking about additional hours logged during daylight hours. Even though it's safer, I think many people are reluctant to turn on their headlights during a storm or at dusk because they think it is harmful to their battery. Is it?

TOM: Using your headlights while you're driving doesn't affect the battery at all. Once the car is running, electricity is produced by the alternator, and the battery is really out of the loop. And while using the headlights does make the alternator work a little harder, the difference isn't enough to worry about.

RAY: There are a couple of very mi??nor trade offs. The headlight bulbs themselves have only so many hours in them, so you will use up the bulbs a little faster. You will also get a very slight decrease in mileage, since producing more electricity requires you to use more gasoline.

TOM: But the costs are so small that they're not even worth considering. What you're getting is increased safety. Remember, the purpose of having your lights on at dawn or dust is not so YOU can see better. It's so other drivers can see YOU, and not crash into you. Anytime there isn't clear day light, it's a good idea to have your headlights on.

RAY: Having said all that, Flora, I'm not sure I agree with your assumptions about why people don't use their headlights more. I think they're just afraid they'll forget to turn them OFF. Now THAT will definitely harm your battery!

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