top of page
  • Writer's pictureJustin Schaub


DC power supply

Not many people are chomping at the bit to work on anything electrical with their car. In fact, most people avoid it, or find that one friend that kind of knows what they are doing. But, if you are going to be a good, well rounded mechanic, you have to dive into some black magic.

When I was in aircraft maintenance school, we were forced to take many different electrical classes, learning the ins and outs of AC, DC, and digital current, and how they applied to the various aircraft systems. During this time, we became very familiar with different power supplies to bench test components. Since cars only have DC power (Direct Current), this is what we will be talking about.

A few years back, DC power supplies were very expensive, and not worth having for the average home mechanic. Since then, there have been some quality Chinese knockoffs, that will do the job for the weekend warrior.

Eventek KPS305D Front

Eventek KPS305D Back

What is a DC power supply?

A DC power supply provides direct current (DC) voltage to power a device under test such as a circuit board or electronic product.

How does a DC power supply work?

A DC power supply works by providing a regulated direct current to power a component, module, or device. Most DC power supplies have two modes of operation. In Constant Voltage (CV) mode, the power supply controls the output voltage based on the user settings. In Constant Current (CC) mode, the power supply regulates the current.

Why you should have one

All of this technical information is good, but you are probably wondering how this will be helpful on your car. BMWs are known to have issues with the coolant systems, but they can also have some electrical gremlins you will have to chase down. Thankfully, we have provided you with free BMW electrical diagrams for your car. Check out the blog below:

The DC power supply allows you to apply 12 volts to any electrical component in your car to test it out. This could include tail lights, gauges, USB ports, or any other module in the car. All of the electrical components will be running on 12 volts.

How to use the power supply

As I stated above, power supplies have come a long way. Not only are they cheaper than ever, but they have safety features built in so it is almost impossible to harm you or the component you are testing. In this blog we are using the Eventek KPS305D 30 volt, 5 amp power supply. Power supplies come in many variations of voltage output and amperage output. Since cars run on 12 volts, the 30 volts is plenty. We also prefer the 5 amp max output as most of the bench testing we will be doing, will only run smaller components that pull less current than this.

Setup is simple. Each power supply has a fine and course adjustment for voltage and amperage. Start by setting the voltage to 12v. From here you can try adjusting the amperage, but the power supply has smart technology that will not allow you to apply more amperage than necessary to run your component. Turn the amperage knobs all the way up. Each power supply include alligator pigtails for testing. Make sure to connect the red and black wires to the red and block knobs.

When you connect an electrical device, the power supply will automatically show you how many amps the device is pulling. In the case of these E30 LED license plate lights, they are drawing .02 amps.

This is great information because one, we know that the lights are working, and two we know the draw on the system. If you were wiring in a new circuit, you could add up all your devices to know what kind of fuse you should use to protect it.

All in all this is a great tool to have in your shop and we highly recommend every mechanic have one. They can save you a lot of time and headache when troubleshooting different electrical components in your car.

If you would like to purchase this power supply, please click the link below.



58 views0 comments

Recent Posts

See All


bottom of page