I think this is a relevant topic because so many people use cell phones and so many people drive. And I’m sure that a significant number of people charge their phones in their cars. It might even lead to more people using resources, whether that’s energy or their money, more efficiently if tested and researched.

I have two myths actually.

Myth 1.
Does charging your cell phone in your car shorten the phone’s battery life?

There would be at least two parts to this test. One where the engine is off and the phone is drawing power only from the car battery. The other part would have the car’s engine running and the engine supplying power to charge the cell phone. The engine-on part may even be split to engine idling and something like car travelling at highway speeds.

Myth 2.
Does charging your cell phone in your car instead in your home, save you money?

This one is based on the idea that the electrical output of a car is replenished once its engines are operational opposed to a homes electrical power that a homeowner is billed for using. This is assuming that your car is an average consumer’s gasoline burning car or even a hybrid perhaps. Nothing like a gas guzzling SUV. There are many factors to take into account including how much you pay for your electricity, gas, car, home, etc.

The amounts of power being measured in both myths is probably very minuscule. I don’t have any ideas on how anyone would go about testing this myth.

This looks like a job for The MythBusters! But until they can test it out, here’s a discussion thread.