How to get household current in your car

Car inverter and laptop charger

CNET

If you want to power a laptop or other large electric device in your car, you need an inverter that turns your car’s 12-volt DC power into 120 volts of AC like you have in your home. Here’s how they work and what to look for when you buy one.

What a car power inverter does 

The name “inverter” doesn’t really tell you much. It should be called a “polarity flipper and voltage amplifier,” but luckily it isn’t. In simple terms, a car power inverter takes the 12-volt DC electricity in your car and alternates its polarity. Imagine if you took the red and black cables on your car’s battery and switched them back and forth quickly: You’d create a crude form of alternating current that looks like this:

Sine wave vs square wave

True sine wave AC power found at a household outlet looks like the smooth waveform at the tip. Rapidly flipping the polarity of a DC power source, like a car battery, results in the crude square wave AC power illustrated at bottom.


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An inverter takes that crude AC and breaks it down into steps so it looks more like the sine wave AC that comes out of a household outlet, while also upping the voltage from 12 to 120. How elegantly the inverter does that is a big part of its cost.

Modified wave AC power

A DC power inverter gradually steps your car’s electric power up and down while also flipping its polarity regularly. The result, shown here in purple, starts to closely resemble the AC you get at home.


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How to buy an inverter for your car

When buying an inverter for your car, add up the wattage of all the things you’ll plug into it. Then add 20% for a safety margin. The inverter you buy should be rated for that total number or higher. 

You’ll also need to decide how good a sine wave you need. A simpler, cheaper inverter will offer “modified sine wave” power on top of that is acceptable for simpler electric devices, like an electric drill or light bulb. 

Amazon

Brand name modified square wave power at a low price.

For laptops and other sophisticated electronics, I recommend a “pure sine wave” inverter which puts out AC that’s virtually indistinguishable from the AC power you have at home. Such an inverter may cost substantially more, but ensures your delicate electronics work and last as they were intended.

Amazon

  An inverter that faithfully replicates the sine wave found in household outlet AC and is rated to power devices up to a combined total of 300 watts.

Finally, check how any inverter connects to your car. Smaller inverters often plug into the 12-volt outlet inside your car while larger-capacity inverters must be wired to your car’s battery. 

With an inverter in your car, you gain a nice margin of preparedness. You’ll know you can power a wide range of electric devices no matter where unexpected plans or emergencies take you.

source: cnet.com