New cable charging slowly? Test it before school

Your phone or tablet seems to charge more slowly with a new cable, and you need it ready for school. Before blaming the cable, compare it with the one that worked before. The charger, outlet, battery level, device temperature, and apps running in the background can all change the rate.

The Charger & Cable Test compares charging speed as a percentage of battery charge per minute. Use it with the same device and charger for both cables. That makes it easier to see whether the new cable is a likely cause.

Compare the new cable with the old one

Start when the device is cool and not close to fully charged. A range such as 20 to 50 percent is useful because charging often slows as the battery fills. Close games, video, navigation, and other demanding apps, or leave the screen off while testing.
Connect the old cable to the charger and outlet you normally use. Open the Charger & Cable Test on the device you are charging, and follow the on-screen instructions.
Note the displayed charging speed in percent per minute. Give the reading time to settle, and keep the device in the same condition while the test runs.
Replace only the old cable with the new one. Keep the same device, charger, outlet, and approximate battery level, then compare the readings.
If the results are close, repeat both tests once under similar conditions. A single reading can change because of battery level, temperature, or activity on the device.

The test is available only on devices whose browser reports battery information. If you do not see it on your device, that does not mean the cable is faulty. Try a supported laptop, tablet, or phone instead.

What the result means

The new cable charges at about the same rate

The test did not find a clear difference between the cables in those conditions. The new cable may be working normally, but this does not prove it can deliver the maximum speed supported by every charger and device. If charging still seems slow in everyday use, check the charger, outlet, and device settings too.

The new cable is consistently slower

If the new cable gives a noticeably lower rate across repeated comparisons, it may be limiting charging or may not be making a reliable connection. Check that both connectors are fully seated, then try the new cable with another compatible charger. If the slow result follows the cable, stop relying on it for a time-sensitive charge and consider returning or replacing it.

Both cables charge slowly

The cable may not be the main cause. The charger could have a lower output, the outlet or power source may be limiting it, or the device could be warm or using power as quickly as it receives it. Try a known compatible wall charger and test again with the screen off.

The reading changes a lot or the test is unavailable

Charging rates can vary as the battery fills or the device warms up. Some browsers also do not provide the battery information the test needs. Repeat under matched conditions if possible. If the tool is unavailable, use the device's own charging indicator and compare one cable at a time.

How to fix slow charging

Reseat the connectors. Unplug both ends and reconnect them firmly. Check for lint or debris in the device port, but do not put metal objects or liquid into it.
Swap one part at a time. Test the new cable with a compatible charger you know works, then test the old cable with that same charger. Changing only one part helps show whether the cable or charger makes the difference.
Check the charger and power source. Use a charger intended for your device and plug it directly into a reliable wall outlet for the comparison. A computer port, car adapter, or low-power USB hub may charge more slowly than a wall charger.
Let the device cool and rest. Remove it from direct sun or a hot bag, stop demanding apps, and leave the screen off. Devices can reduce charging when they are hot, and some naturally slow the rate as the battery approaches full.
Check charging limits and battery status. On Windows 11, open Settings › System › Power & battery. On macOS, open System Settings › Battery. On an iPhone, open Settings › Battery; on Android, open Settings › Battery, though names vary by manufacturer. Look for a charging limit, optimized charging, or a battery warning that could explain why charging pauses or slows.
Try a different outlet and retest. If the rate stays low, use another wall outlet and repeat the comparison at a similar battery level. If both cables are slow with one charger but charge normally with another, the charger is the stronger suspect.

When the cable or charger may be damaged

Stop using a cable with exposed wires, a cracked connector, a loose fit, or unusual heat. Do not keep testing a charger or cable that smells burnt, sparks, or becomes uncomfortably hot. Replace damaged accessories with compatible products from a trustworthy source. If a known-good cable and charger still charge the device poorly, the charging port or battery may need inspection by the manufacturer or a repair shop.

What a percent-per-minute reading can tell you

The result is a practical comparison, not a direct measurement of watts, voltage, or current. Charging speed depends on the device, charger, cable, battery level, and temperature working together. A cable can also support different charging speeds depending on its design and the charging standard shared by the device and charger. The test can help you spot a repeatable difference, but it cannot certify that an accessory is electrically safe or prove its advertised specifications.