Using a Power Outlet Socket for Car Accessories

In the last two decades, we’ve seen increased deployment and usage of additional power outlets in the automobile. Back in the 70s and 80s this outlet was mostly used to ignite tobacco. These days some motorists attempt to run an electronic empire from this small outlet. Although manufacturers have increased the capabilities and added additional outlets there are still limitations on just how many accessories can be run at one time. This article will identify the difference between a cigarette lighter socket and a power outlet. Also discussed are best practices when plugging in new accessories. Finally we cover common problems that can blow fuses in the car’s main panel.

Cigarette Lighter vs. Power Outlet

Sometimes, car owners don’t realize there is actually a difference between a cigarette lighter socket and a power outlet. The lighter uses a heating element that automatically releases from the pushed in position when fully heated. On the socket side a power outlet has a center positive contact and uses the shell as a ground. Cigarette lighter sockets have a specially designed center electrode to contact and heat up the coiled element.

Although the difference in construction of the socket seems like a small detail what it actually means is a power accessory can be driven from the cigarette lighter socket, but a cigarette lighter cannot be inserted into a power outlet and achieve the desired results. This is one reason that from the factory a cigar lighter is installed in an outlet that supports it and a black cover is snapped over a power outlet that does not support ignition of tobacco products.

How Much Load can a Power Outlet Handle

Drivers want to know how much power an accessory outlet can handle without causing problems. Although I will provide a general answer a specific one can be found in the owner’s manual. After the car is running the size of the battery is not as important as the output of the alternator. Therefore how much power can be supplied varies between models. A small compact car with a tiny alternator will not be able to drive large accessories. Police cars with high output alternators can.

As far as the general answer to the question how much I can run from a power outlet, on my specific car the answer is 120 Watts, but not to exceed a twenty amp current draw. The socket is designed to run a 12 V automotive plug with a positive center contact and shell ground. Most accessories like car chargers or ones with this type of plug installed will list how much power it draws and directions for usage.

As an added convenience and selling feature for people who are looking to plug things into a car like they would their house, vehicle manufacturers are adding AC outlets, especially to sport-utility vehicles. These outlets connect to a factory installed power inverter that turns direct-current into alternating current. Although the outlet looks like something you would find in a house it does not carry the same power. In fact, many of these outlets have 150 W limits. This means you will not be plugging in that 1500 W hairdryer or a full size refrigerator on the family camping trip.

Problems Caused by Outlet Overloading

There is a certain group of motorists that are always searching for more power to plug-in additional accessories and devices. Things like laptops, heaters and hairdryers are notorious for drawing lots of power. Aftermarket accessory designers in an attempt to appeal to these motorists have manufactured adapters that turn one power connection into three or more. Running multiple accessories will only be as successful as the amount of power they draw. The good news is an accessory outlet is well protected. If a 1500 W hairdryer is plugged in it will simply blow the fuse and stop working.

Accessory Socket Blows Fuses

Most power outlet sockets are protected by a fuse installed in the main panel. On some automobiles the fuse says power accessories while other car makers will label it courtesy or cigarette lighter. When this blows problems are common in two areas.

First, it is possible for debris to get down inside the socket and short the center positive terminal to the shell ground. A good example of this would be some change like a nickel or dime falling down inside. Paperclips and other metal objects can also open the fuse.

The second common cause would be a problem with the accessory inserted into the power socket. In the example of a cell phone car charger the base that plugs in contains electrical components to convert the cars 12 V twenty amp power supply into whatever the cell phone needs to provide a fast charge. Therefore, it’s possible for components to fail in the charger itself. When this happens, it can either blow the fuse or not work properly in its task of charging the phone.

In conclusion, whenever your plugging in a new gizmo or contraption that’s designed to operate from an automotive power outlet there will be some type of documentation about the amount of power it draws and directions for its usage. Often these are stickers or tags directly attached to the device. These specifications can be measured against vehicle specific ones located in the owner’s manual. As a general rule of thumb anything exceeding a twenty amp draw will blow the fuse.