How to test a USB-C power supply when your SBC has power issues

Power problems are one of the most common causes of instability, boot failures, or random restarts in single board computers (SBCs). Because many modern boards use USB-C connectors for power, it’s important to verify that your power supply is delivering the correct voltage and current before assuming there’s a hardware fault.

Check the basics

Start by confirming that your USB-C cable and adapter are rated for your board’s requirements. Most SBCs need 5 V at 3 A (15 W). Some boards, like the Orange Pi 5 or Raspberry Pi 5, may negotiate 9 V or 12 V via USB Power Delivery (PD), depending on their design. If you’re using a phone charger or low-power adapter, it may not provide enough current, even if it fits physically.

Use a USB power meter

A simple USB-C inline power meter is the easiest way to test. Plug the meter between your power supply and SBC, then read the live voltage and current:

• Voltage should stay close to 5.0 V (or the PD voltage) even under load.
• Current draw will vary, but if it exceeds your adapter’s rating, the voltage may drop and cause instability.
  If you see voltage dropping below 4.8 V, your cable or power brick is likely under performing.

Test with a known good supply

If possible, test the board with a different high-quality USB-C PD charger or a dedicated SBC power adapter. Avoid cheap generic units some fail to maintain stable output when current spikes during CPU or GPU activity.

Check for cable quality issues

USB-C cables vary widely in thickness and resistance. A thin or data-only cable can limit current flow. Look for cables rated for 3 A or 5 A charging.

Measure with a multimeter (optional)

For a deeper check, you can measure voltage directly at the SBC’s power input pads or test points using a multimeter. This reveals if voltage drops occur between the connector and the board.

Monitor behavior under load

Boot your SBC and run a stress test (for example, stress-ng or sbc-bench). Watch for throttling, reboots, or USB devices disconnecting signs that the power source can’t keep up.

Bottom line: A stable USB-C power supply should maintain consistent voltage under load, use a properly rated cable, and meet your SBC’s full current requirements. Testing with a meter or swapping components systematically can quickly reveal whether power, not the board, is the real culprit.