How to test a replacement charging cable

Your replacement cable fits, but is your phone or laptop charging as quickly as before? A cable can affect charging, but the device, charger, battery level, and temperature also change the rate. A fair comparison helps you find out whether the new cable is the likely cause.

Use the Charger & Cable Test to compare charging speed as a percentage of battery charge per minute. It works only on devices whose browser reports battery information, such as some phones, tablets, and laptops. It does not measure the cable’s exact wattage or certify its safety.

Compare the replacement cable

Open the Charger & Cable Test on the device you want to charge. Connect the charger and check that the tool reports a battery and charging speed. If it does not show battery information, use the device’s battery indicator for a rough comparison instead.
Use the same device, charger adapter, wall outlet, and charging conditions for both cables. If possible, first test the old cable, then the replacement cable. Do not compare a wall charger with a computer USB port, since their available power can differ.
Begin each comparison at a similar battery level. Charging often slows as the battery gets closer to full, so a result from 25 percent is not directly comparable with one from 85 percent.
Leave the device idle for several minutes while the cable is connected. Note the tool’s percentage-per-minute reading after it settles, then repeat with the other cable under the same conditions.
Repeat the comparison once if the readings are close or keep changing. Keep the screen off if practical, and do not run demanding apps during either test.

If you have no old cable to compare, test the replacement more than once with the same adapter and outlet. That can reveal whether charging is steady, but it cannot prove the cable matches a particular speed rating.

What the result means

The replacement cable charges at a similar rate

A similar reading suggests the new cable is not causing a noticeable slowdown in this setup. It does not confirm that the cable supports data transfer, every fast-charging standard, or safe operation under all conditions.

The replacement cable is consistently slower

If the difference repeats under comparable conditions, the cable may have more electrical resistance, a damaged wire, or limited support for your device’s charging method. Check the cable’s specifications and try another known-good cable before deciding the charger or device is at fault.

The rate is low with both cables

The charger, outlet, charging port, temperature, or battery level may be limiting the result. Some devices slow charging when warm or nearly full. Test again when the device is cool and at a lower charge, then check the adapter and outlet.

The device does not show that it is charging

Check that the connector is fully seated at both ends. If another cable works in the same setup, the replacement cable may be faulty or incompatible. If neither cable works, inspect the adapter, outlet, and charging port.

How to fix a slow or inconsistent result

Check the connection. Unplug both ends and reconnect them firmly. Look for lint or debris in the device port, but do not push metal objects into it. Stop if the connector feels loose, looks damaged, or becomes unusually hot.
Try a different wall outlet. Keep the charger adapter and cable unchanged. Avoid power strips or USB ports during this check, since they introduce another possible cause.
Compare with a known-good cable. Use one that is suitable for your device and charger. If the known-good cable charges normally but the replacement repeatedly does not, return or replace the new cable.
Check the adapter and charging mode. A cable cannot make an adapter provide more power than it supports. Confirm that the adapter is compatible with the device’s charging standard and has enough capacity. A fast-charge label alone does not guarantee that every device and cable combination will use fast charging.
Check temperature and charge limits. Let a hot device cool before testing, and check whether a charging limit is active. On Windows 11, open Settings › System › Power & battery. On macOS, open System Settings › Battery. On Android, look under Settings › Battery or Settings › Battery and device care › Battery. On iPhone, open Settings › Battery. Menu names vary by model. A charge limit or optimized charging feature may pause or slow charging near its target.
Inspect the cable for damage. Check for bent connectors, exposed wire, fraying, or a loose fit. Do not keep using a cable that is damaged, smells burnt, or heats up abnormally.
Restart the device and retest. A restart can clear a temporary charging or battery-reporting issue. Compare again with the same adapter, outlet, and approximate battery level.

When the cable needs replacing

Replace the cable if it only charges when held at an angle, repeatedly disconnects when moved gently, or shows visible damage. Do not bend it repeatedly to force a connection. If multiple known-good cables behave the same way, the port or charger may need service. A damaged device port should be checked by the manufacturer or a repair shop rather than probed at home.

Why percentage per minute is not the same as watts

The test reports how quickly the battery percentage rises, not the electrical power entering the device. Battery capacity differs between devices, and charging speed changes with battery level, temperature, screen activity, and the charging system’s decisions. Use the result to compare two cables on the same device under similar conditions, not to compare the charging power of different phones or laptops.

If the browser does not report a battery, the Charger & Cable Test may not appear on that device. A battery icon that changes while charging can confirm basic operation, but it is not a precise cable-speed measurement.