How to compare charging through two USB-C ports
Compare two USB-C charging ports with the same device, cable, and battery level. See how to read the rate and tell a port problem from a setup issue.
Two USB-C ports can look identical but charge at different speeds. One may not accept charging at all, or the rate may change because of the cable, charger, battery level, or apps using power.
To compare fairly, change only the port and keep the rest of the setup the same. The Charger & Cable Test measures charging speed as a percentage of battery per minute. It measures the result on your device, not the port's exact electrical wattage.
Compare the two USB-C ports
- Open the Charger & Cable Test on the device you are charging. The tool appears only when the browser reports battery information, which is usually on a laptop, tablet, or phone.
- Check that the first port can charge the device. Some USB-C ports transfer data or video but do not accept power. Look for a charging symbol or check the device's manual.
- Connect the same charger and USB-C cable to the first port. If you are comparing two outputs on one charger, move the same cable from one output to the other. Disconnect other devices from the charger so they do not affect its shared power.
- Keep the device's use and battery level similar for both tests. Close demanding apps, leave the screen at the same brightness, and compare within a similar battery range, such as 30% to 50%.
- Note the rate in % per minute after charging for about 10 to 15 minutes. Repeat the test on the second port with the same setup. For more confidence, compare each port more than once under similar conditions.
If the battery is already near full, the device may slow charging to protect it. A very low battery, a hot device, or heavy app use can also change the result, so avoid comparing tests made under noticeably different conditions.
What the result means
One port has a consistently higher rate
The device charged faster through that port during your tests. This can happen when the ports support different charging capabilities, or when one connection negotiates a higher charging rate with the charger and cable. Repeat the comparison before concluding that the slower port is faulty.
The rates are close
The two ports performed similarly in this setup. That does not prove they have the same maximum charging capacity. The charger, cable, device, or battery level may be limiting both results.
The rate changes a lot between attempts
The conditions may not be consistent enough to compare. Battery charging often slows as the battery fills, and background activity or heat can change how much power is available for charging. Repeat the tests at similar battery levels, with the same screen and apps.
There is no rate, or the battery does not charge
The browser may not report battery information, so the tool cannot show a result. If the device does not charge either, confirm that the port accepts charging and check the charger and cable before assuming the port has failed.
How to get a fair comparison
- Check the port's purpose. USB-C describes the connector shape, not every feature it supports. Consult the device manual or markings to check whether each port accepts charging.
- Use one charger and cable. Keep them unchanged while you switch ports. A cable that is damaged or not suited to the charger's capabilities can limit charging, even if the port is fine.
- Remove other devices from the charger. Some multiport chargers share available power among connected devices. Disconnect other cables before each run and use the same wall outlet.
- Keep device use steady. Close games, video editors, and other demanding apps. On Windows 11, check Settings › System › Power & battery. On macOS, check System Settings › Battery. Keep the power settings and screen brightness the same for both tests.
- Let the device cool if it is warm. Charging can slow when a device gets hot. Let it return to a similar temperature before retesting, and do not cover it while charging.
- Repeat with another known-good cable if needed. If one port still appears slower, try a cable and charger that you know work correctly. Change one item at a time so you can identify what affects the rate.
When the port may be faulty
A low rate by itself does not prove that a USB-C port is damaged. A stronger sign is that the device repeatedly fails to charge through that port with a known-good charger and cable, while another charging port works under the same conditions. A loose connection, visible damage, or charging that stops when the cable moves also points to a possible hardware problem.
Do not force the connector or put tools into the port. If the port is loose, damaged, or unreliable after testing with known-good equipment, contact the device maker or a repair shop. If the device is under warranty, ask the manufacturer about service before attempting a repair.
What the rate can tell you
A percentage-per-minute result is useful for comparing charging on the same device, but it is not a direct measurement of watts. Battery size, battery level, temperature, and the device's own charging controls all affect how quickly the percentage rises. Use the result to spot a repeatable difference between setups, not to claim an exact power rating for a port.
