Most cigarette lighter sockets are rated for 15-amps or so. Look at the fuse to confirm this, it’s probably a 15-amp fuse. Ohms / watts law says you will only get 207 watts out of a lighter plug. 13.8 volts times 15 amps comes to 207 watts.

If you want or need more then that, you should run a new line from the battery with stranded wire (don’t use Romex or any other solid wire) to wherever you are going to mount the inverter. Don’t use a cigarette lighter plug, if you buy one from Radio Shack they are rated for only 10-amps according to the package.

Hard wire it to the inverter or buy Anderson plugs or pole connectors.

300 amp arc welding cable would be a good choice.



Inverters pull a lot of power out of a battery without the auto running they will kill the battery fast. A 400 watt inverter draws 28 amps when running at capacity. And that doesn’t take loss or less then 100% efficiency into account.


An auto battery is not made to be drained like a deep cycle battery, do this a few times and you will be buying a new battery.