I would like to hard-wire a 4-port usb hub to my cig outlet. I currently have the hub connected to my power inverter and have to flip a switch to turn on the power. My goal is to do a complete behind-the-dash solution where I don't need to flip a switch. I have clear access to the cig outlet in the dash (I would prefer to cut as little as possible but since I don't smoke I really don't care if I need to hack something). I checked the outlet with my multimeter and confirmed that power is only switched on/off with the ignition which is exactly what I want.

My original thought is to just take apart the hub's power adapter and connect the wiring to the cig outlet. The power adapter is just converting 12v down to 5v anyway so I could just solder the connections to the outlet right? I haven't taken apart the adapter yet, I just wanted some confirmation that my thoughts are correct before I do it. If I'm way off or something, what are some other solutions I could do? It's been a while since I've done anything with electronics so my memory is a bit rusty.

  • \$\begingroup\$ You say you use a power inverter, which normally converts 12v DC to 120v AC. Is that what you have? \$\endgroup\$
    – Passerby
    Sep 2, 2013 at 0:20
  • \$\begingroup\$ yes, that's it. \$\endgroup\$ Sep 2, 2013 at 0:28
  • \$\begingroup\$ I'm confused. Is the power adapter something you plug into the wall outlet to convert 120Vac to 5Vdc or does it convert 12Vdc to 5Vdc? Is it part of the hub or a separate thing? Why are there two heads in your profile photo, and which one is you? \$\endgroup\$
    – Joe Hass
    Sep 2, 2013 at 2:52
  • \$\begingroup\$ If the hub is designed to be used with 120VAC then it can't be used with a 12VDC source. \$\endgroup\$
    – Oli Glaser
    Sep 2, 2013 at 3:20
  • \$\begingroup\$ @JoeHass a car power inverter allows for some ac devices to connect to a car. en.wikipedia.org/wiki/File:Inverter_CJC01.jpg \$\endgroup\$
    – Passerby
    Sep 2, 2013 at 3:52

1 Answer 1


Fundamentally, it would be easy to do. 4 Port USB hubs normally require 2 Amps of 5v power. You can get 12v to 5v 2+ Amp supplies quite easily. They can be wired in parallel to a cigarette lighter. Cigarette Lighters are typically on their own 10 to 15 Amp fused circuits, and most are switched, so they are only powered when the car's ignition is set to ACC/On.

BUT from your question and comments, you have a 12v DC to 120v AC inverter, and plug in a home/office usb hub power supply. You COULD replace the cigarette lighter with the inverter, wiring it in. Some cars even come with that as a standard option. Just remember, this is atleast 120W of energy on the car side, and 120v at the inverter side, so wiring could be dangerous. Here is an example of a large 400W inverter wired in (cable to battery) and modded to the center console of a car. Smaller single port inverters could just replace the cigarette lighter without needing to run a cable to the battery, using the cigarette lighter fuse and it's own fuse as the protection.

That said, the three easiest, probably cheaper ways of doing it, would be getting a 2 amp 12v to 5v power supply and wiring that to your usb hub, or getting a 4 port usb car charger, or getting two 2 port usb car chargers for like 5 bucks and wiring those in. People Hardwire usb ports in their dash or center console all the time.

BUT the MOST IMPORTANT THING IS, making sure that the circuit you use, is switched. If it is not, that means the circuit is always powered, even with the car off and key removed. If you can use the cigarette lighter like that (car off, key out), you run the risk of the power supply or inverter you are using to drain your battery. Replacement car batteries arn't cheap, and at best, having to get jumped in the morning would ruin your day.

  • \$\begingroup\$ Thanks for the lengthy write-up. I ended up changing my plans a bit when I noticed I could do something easier with parts I already had laying around. I basically scrapped the idea of the 4-port usb hub (which was going to power a usb cord for my cell phone) and just decided to hard-wire the usb cord itself to the 12v on the cig outlet. I soldered a 5v regulator to the usb cord and to the 12v coming from the outlet. This has switched power so it only charges when the car is on ACC/ON which is perfect. \$\endgroup\$ Sep 2, 2013 at 18:53

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