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Plugging computer into car

Hi, I bought an adaptor that converts my cigarette lighter outlet into a 3-prong electrical outlet. Now I can keep my computer charged while driving on long road trips. Does this waste gas? Or does the engine produce an excess of electricity for the car battery so that I’m actually getting some free energy?

Yes it does use gas to run that adapter for your computer.
However, the amount of incremental fuel used will be so minute, it would take some very expensive sophisticated equipment to even be able to measure it.

So consider it “free” because the amount is so small you will never ever notice any change in mileage.

Many people never quite grasp the concept that the amount of electricity generated depends on the load. I see this a lot when people think a large power suppy will somehow “push” a damaging amount of electricity through their computer. It is not the engine that produces electricity but the alternator (that is driven by the engine). The amount of electricity produced by the alternator is dependant on the load placed on the cars electrical system,low load, low output.This is the same as asking if your car gets better mileage with the headlights on or off.

You won’t have a problem with your car, but I hope you got a powerful enough inverter, because otherwise you might have issues if you run your computer while it’s plugged in to the inverter.

Not really. The more powerful laptops only consume at most around 100 watts. Most will weigh in at around 60-90 watts. Even the most basic of inverters can handle that.

If you measured your fuel consumption for a trip from California to New York and back, with the power inverter plugged in and with no power inverter, you will not notice any measurable difference in fuel economy related to the inverter being plugged in. If you were to go on a trip to the moon and back and took the same measurements, you may notice you used a small amount more gas with the inverter plugged in. It’s not worth fretting about.

Thanks for the info guys. It was the effect on gas mileage that interested me; it’s nice to know the computer will mean very little.

Personal experience talking here. I had a 75 watt laptop on a 75 watt inverter on a mount that I used for GPS. The trouble came if I had used the laptop on battery at all, because then it was drawing running power plus charging power, and overloaded the inverter.