USB power meter: compare charging cables fairly

Use one charger port without other devices sharing its power. Choose undamaged cables rated for your charger and phone. Let the phone cool, close demanding apps and leave the screen off during each reading.

Start below your phone’s charge limit. Charging often slows as the battery fills, so compare at similar battery percentages. Wait for readings to settle rather than choosing the biggest number that flashes past.

Write down each cable’s voltage, current and power, plus the battery percentage. Repeat the comparison if the first cable’s reading changes. If everything drifts, you have not isolated the cable yet.

Watts describe what this charging setup is delivering now, not the maximum printed on the charger. Temperature, battery management and charging negotiation can change the reading without anything being faulty.

A single reading does not measure cable resistance or certify data speed, battery capacity or safety. The meter adds its own connections and measurement uncertainty. Tiny differences are not a reason to replace a cable.

Plugable documents USB-C PD 3.1 EPR support up to 240W, but excludes Thunderbolt 3 devices. Follow every component’s ratings; do not force voltages or use adapters to chase a higher number. Stop if a cable, connector or device becomes unusually hot.