Turn Your Old Laptop Charger Into USB-C Charger!

Got an old laptop charger lying around? Don’t throw it away just yet! While it may no longer fit your devices, it still delivers powerful DC output — perfect for re-purposing. In this DIY project, I’ll show you how to convert that outdated charger into a functional USB-C power supply using a simple DC-DC converter module.

This beginner-friendly build teaches valuable electronics skills like voltage regulation and polarity, while also helping reduce e-waste. Whether you want to power an Arduino, charge your phone, or create a custom power solution, this is a great way to give new life to old hardware — all while learning something useful and practical.

1x Fast Charging Module

1x Male-Male USB-C connector

1x Soldering Iron

1x Pliers

Most old laptop chargers output a DC voltage between 18V and 20V — much higher than the voltage USB-C devices expect (typically 5V, 9V, or 12V). Directly connecting your charger to USB-C devices can damage them due to this high voltage. To safely adapt the voltage, you’ll need a DC-DC step-down (buck) converter or a fast charging module designed for USB-C outputs. These modules regulate and step down the voltage to standard USB-C power levels while supporting fast charging protocols

Laptop chargers typically have two wires: positive (+) and negative (-).

If unsure, refer to your charger’s specifications or search online for your model’s wiring diagram.

Use a multimeter set to DC voltage to confirm which wire is positive and which is negative.

Carefully strip the insulation from the wire ends, exposing about 1 cm of wire for connection.

Double-check your polarity before proceeding to avoid damaging the charging module.

Connect the positive wire (+) from the charger to the module’s input positive terminal.

Connect the negative wire (-) from the charger to the module’s input negative terminal.

Ensure the connections are solid: solder the wires if possible, or use secure screw terminals.

Use heat shrink tubing or electrical tape to insulate exposed wires and prevent shorts.

Before connecting any devices, plug the charger into the wall outlet. Using the multimeter, measure the voltage at the USB-C output terminals of the module. Confirm the output voltage matches the expected USB-C voltage (usually 5V or 9V).

If the voltage is off or fluctuates, disconnect immediately and re-check your connections.

To ensure safety and durability, consider housing the entire circuit in an enclosure. A plastic project box or custom 3D printed case works well to protect the wiring and module. This prevents accidental short circuits and protects you from electric shock. Secure the charger cable and USB-C output cable so they don’t pull on the connections.

Always work with the charger unplugged while making connections. Avoid touching exposed wires or terminals when the charger is powered. If the charging module or charger feels hot during use, unplug and inspect for wiring errors or faulty components.

Use a fuse or circuit breaker in your setup if possible for extra protection. Never exceed the rated current of your charging module to prevent damage.

This simple project helps reduce e-waste by giving your old charger a second life.

It introduces you to fundamental electronics concepts such as voltage regulation, power conversion, and USB-C charging protocols.

The resulting USB-C power supply is versatile — ideal for charging phones, powering microcontrollers like Arduino or Raspberry Pi, or providing stable power to USB-C devices.

It’s portable, cost-effective, and a great addition to any maker’s toolkit!

Once everything is assembled and enclosed, test the charger with various USB-C devices.

Check that the devices charge properly and that the charging speed corresponds to the supported fast charging standards.

If you notice any irregular behavior (overheating, device not charging), disconnect and re-check your setup. Always unplug the charger if unused for long periods.

Congratulations! You’ve just transformed an obsolete laptop charger into a functional USB-C power supply — all while learning about voltage conversion, polarity, and USB charging standards. What once was destined for the landfill is now a powerful tool on your electronics workbench or in your everyday setup.

This DIY project is more than just a clever hack — it’s a hands-on way to dive into practical electronics and sustainability. You’ve learned how to safely handle and adapt DC power, use a step-down converter, and create a safe, functional output for today’s USB-C devices. It’s an ideal introduction to working with power electronics and a great gateway into future maker projects.

And best of all, you’ve done your part to combat electronic waste. In a world where chargers and cables are constantly changing, this project gives new life to old tech — proving that with a little creativity and some basic knowledge, you can reduce waste and save money at the same time.

So whether you're powering an Arduino, charging your phone, or building your own bench power supply, this repurposed charger is proof that old electronics still have plenty of spark left. Keep tinkering, keep building — and never underestimate what you can do with what's already in your drawer.