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How To Make Car Charger Work When Car Is Off?

by Jordan Harris
How To Make Car Charger Work When Car Is Off

For folks like me who are constantly on the move, you might understand the inconvenience of your car charger not working when your car is off. So, how to make your car charger work when your car is off?

It can be particularly frustrating when your 12V charger or cigarette lighter charger is not working when you need to charge your devices on the go. However, there is a way to re-wire and modify it otherwise.

By installing a separate relay to the car charger outlet while also making sure that it’s connected directly to your battery, you can then install a toggle switch to turn it on and use it, even when your car is off.

Safety Precautions & Considerations

If you’re wondering how to modify your car’s charging system to keep it active even when the car is off, you’re in the right place. But first, there are a few important safety considerations to be wary of…

  • A service manual with a complete wiring diagram for your car is essential. This will help you identify the 12V outlets and their connections. So, make sure you have this handy before you begin modifying.
  • Once you’ve modified the car charger, remember that charging small devices (i.e. phones) won’t drain a healthy car battery, but other devices, and leaving your lights on can have a more significant impact.
  • It’s essential to ensure your car battery is in good health and to be mindful of what you leave plugged in and turned on. Too much drain can harm your vehicle’s electrical system or kill the battery for good.
  • If you’re not comfortable with electrical work, it’s always a good idea to seek professional help. Modifying your car’s electrical system can be risky, and it’s vital to ensure everything is done safely and correctly.
  • Modifying your car’s electrical system might void the warranty. Therefore, always check with your car manufacturer’s warranty terms or call the dealership beforehand prior to making any changes.

Step-By-Step Guide To Modify Your Car Charger

With that in mind, and once you’re ready to consider making modifications to your car charger to make it work even when your car is turned off, I’ve prepped a quick set of instructions that you can refer to.

Here’s a quick preview of what this entire process will entail (click on each one to skip ahead to that step):

1 – Gather The Necessary Tools And Materials

How To Make Car Charger Work When Car Is Off

Here’s a list of tools, materials, and other equipment and must-haves that will help with expediting the process of modifying your car charger:

  • Service manual with a detailed wiring diagram for your car
  • Relay and fuse
  • 14-12AWG wire
  • SPDT toggle switch rated for 15ADC or higher
  • Wire stripper, cutter, and crimping tool
  • Electrical connectors and electrical tape

2 – Study The Wiring Diagram

  1. Using your car’s official service manual, identify the 12V outlets on the wiring diagram.
  2. Determine if they are connected directly to the battery (B+) or through a relay that activates with the ignition.
  3. The modification is highly dependent on your car’s make, model, and the physical distribution of the outlets within the vehicle.

3 – Locate The 12V Outlet Wiring In Your Car

  1. Depending on your vehicle, this might be located behind the dashboard, under the center console, or in another accessible area.
  2. Outlets that are always on are typically connected directly to your car’s battery (B+) via a 15A fuse.
  3. Those that work only when the key is in the ignition are connected to a relay that activates with the ignition or accessory key positions.

4 – Install A Relay

  1. If your outlet is ignition-dependent, consider adding a separate relay in parallel with the existing one. This will allow you to control the power source manually.
  2. Then, you can now run dedicated wires (14-12AWG) to each DC outlet.
  3. You can install a toggle switch to alternate between the always-on and ignition-dependent 12V supplies. Also, make sure the switch is rated for 15ADC or higher.

5 – Wire The Toggle Switch

  1. Connect one end of the switch to the always-on power source (direct battery connection) and the other to the ignition-dependent source.
  2. The center terminal of the switch should be connected to the 12V outlet. This will allow you to choose between the two power sources manually.

6 – Test The System

Before finalizing the setup, test the system to ensure it works correctly. Turn off the ignition and flip the toggle switch to the always-on position. Your 12V charger should now work even with the car off.

7 – Secure All Connections

Ensure all electrical connections are secure. Use electrical tape or connectors to prevent any loose wires.

By following the steps above and taking necessary precautions, you can modify your car’s 12V charger to work even when the car is off. If you’re not comfortable with this, please do consult a technician.

This little mod can be particularly useful for long trips, camping, or any situation where you might need to charge devices without having to manually start your car every single time.

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