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Can I Use a Cigarette Lighter Inverter?

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Some cigarette lighter inverters come with one or more built-in USB power ports.

Image courtesy of jamuraa, via Flickr (Creative Commons 2.0)
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Question: Can I use a cigarette lighter inverter in my car?

I got an inverter, but I’m not sure exactly how to hook it up. The one I got has a couple of different kinds of wires that came with it. One is a cigarette lighter plug, and the other is alligator clips (so I guess it’s for just clipping on to the battery terminals?) I don’t really want to have to run wires all the way to the battery, and I’m not sure if the ones it came with are long enough anyway. So I’m wondering if it’s okay to just use the cigarette lighter part and call it good.

Answer:

The short answer is that yes, it’s perfectly fine to use a cigarette lighter inverter in your car. However, the real answer is a whole lot more complicated than a simple yes or no. While there’s nothing wrong with plugging an inverter into your cigarette lighter socket (or any 12V accessory socket for that matter), there are some pretty hard limitations on what you’ll be able to power with that type of connection.

If the electronics you want to plug in draw less amperage than the cigarette lighter fuse is rated for, then you’ll be fine. That’s typically about 10 or 15A, but you’ll need to check yours to be sure. If you need more amperage than that, then you’re going to have to figure out a different wiring solution. And, unfortunately, the alligator clips probably aren’t going to cut it.

See: Car Battery Inverter Connections

The Problem With Plug and Play Cigarette Lighter Inverters

While cigarette lighter inverters are extremely convenient, they all suffer from the same limitation. Unlike inverters that are wired directly to a car battery (or to a dedicated circuit), a cigarette lighter inverter draws power from the cigarette lighter circuit. That means you can’t put a load on this type of inverter that draws more current than the cigarette lighter fuse can handle, or you’ll blow the fuse.

In addition to this limitation, you also have to consider the fact that the cigarette lighter circuit may have more on it than the lighter socket. These circuits often have additional 12V accessory sockets tied into them, and they sometimes also provide power to dash lights, the head unit, and other items. If the cigarette lighter circuit in your vehicle has any of these additional loads, that further diminishes the amount of current you can draw from an inverter that’s plugged into it.

Bigger Isn't Better (When It Comes to Fuses)

Before you swap out your 10A cigarette lighter fuse with a bigger one, consider the fact that the folks who designed your vehicle’s electrical system weren't dummies. Every fuse in that fuse block is sized appropriately for the corresponding circuit, and those fuses serve a vital function, in that the will sacrifice themselves to save the rest of the circuit (and, in some cases, to even prevent a fire.)

If you simply replace your cigarette lighter fuse with a bigger one, you might be fine. But since the circuit in question was only designed to handle 10A (or whatever the fuse is rated for in your case), you might also be in for a world of hurt.

Say, for instance, that some of the wiring in the circuit is only designed to handle a little over 10A, and say that you plug enough stuff into your cigarette lighter inverter to pull 20A. Those dinky little wires are now going to be the primary point of failure instead of the now beefier fuse. In a best case scenario, you’re then looking at some inconvenient, costly rewiring. If you aren’t that lucky, you might end up with an electrical fire on your hands.

So What Can You Plug into a Cigarette Lighter Inverter?

In order to find out what you can safely plug into a cigarette lighter inverter, you’ll need to do a little homework. First of all, you’ll have to find out the size of your cigarette lighter fuse. You’ll then have to find out how much amperage your equipment draws. If a device draws less amperage than the cigarette lighter circuit is rated at, then you’re probably going to be fine.

Of course, you have to remember that there is a difference between the amperage that an AC device draws and the amperage that the inverter draws in order to convert the ~12V DC from your car’s electrical system into 110V AC. A general rule of thumb is that a cigarette lighter inverter shouldn’t draw more than 100-120W, and some dual-use car power inverters like the one you’re describing are actually wired with this in mind. If that’s the case, you’ll find that your inverter will be limited to something like 100W when plugged into the cigarette lighter, and it will be able to handle its full continuous rating when you hook it into the battery.

Some of the devices you can probably plug into a cigarette lighter inverter include:

  • laptops
  • DVD players
  • handheld video game chargers
  • digital music players (i.e. iPod)
  • cell phone chargers

Of course, anything that you can safely plug into a cigarette lighter inverter you can also power directly from a 12V accessory socket with the correct adapter, which is much more efficient.

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