Why charging speed drops near 100 percent

Your phone or laptop charges quickly at first, then seems to crawl through the last few percent. In most cases, that slowdown is normal. Devices reduce charging power as the battery fills to limit heat and protect the battery.

You can compare charging rates with TooLab’s Charger & Cable Test. It reports charging speed as percent per minute when your browser can access battery information. The result is most useful when you compare chargers or cables at similar battery levels, not when the device is almost full.

Compare charging speed fairly

1. Open the Charger & Cable Test on the device you want to check. The tool appears only if the browser reports a battery for that device.
2. Connect the charger and cable you want to test. For a useful comparison, start at a middle charge level, such as 30 to 60 percent, rather than close to 100 percent.
3. Keep the device and conditions steady while you observe the rate. Leave the screen in the same state for each test, and avoid running games or other demanding apps.
4. Repeat the test with one change at a time, such as a different cable or charger. Compare the results over a similar range of battery percentages.

If your browser does not show a charging rate, that does not mean the charger is faulty. Some phones and browsers do not provide battery data to web pages. The Battery Meter has the same device-reporting limitation.

What the result means

The rate falls as the battery gets close to full

This is expected. A battery accepts power more readily when it has room to charge. Near full, the device gradually reduces the current, then may pause or add small amounts of charge to maintain the level. It can take longer to move from 90 to 100 percent than from 50 to 60 percent.

The rate is low only near 100 percent

That alone is not a sign of a bad charger or cable. Battery percentages are rounded estimates, so the displayed number may stay still even while charging continues. A charge limit or optimized charging feature may also pause charging before full, then finish later.

One charger is consistently slower at the same charge level

The charger, cable, port, or charging mode may be limiting power. A device may also draw less power from an adapter that does not support its preferred charging method. Compare results at a similar battery level and temperature before deciding that one part is faulty.

The rate drops sharply at different battery levels

Heat, heavy device use, a loose connection, or a battery problem can all reduce charging speed. A browser test reports a change in charge percentage over time, not the charger’s exact wattage, so use it to compare conditions rather than diagnose a specific part by itself.

How to improve a slow charge

1. Check whether the slowdown is simply the final charge phase. If the rate falls mainly above about 80 percent and the device reaches full eventually, it is usually normal. Compare chargers at a lower, similar charge level instead.
2. Let the device cool and reduce its workload. Charging can slow when a phone or laptop is hot, in direct sun, or running demanding apps. Unplug it if it feels unusually hot, let it cool in a safe place, and avoid covering it while charging.
3. Check for a charge limit or optimized charging. On Windows 11, open Settings › System › Power & battery and check the battery options available on your computer. Some manufacturers put charge limits in their own utilities. On macOS, open System Settings › Battery and review the battery health and charging options. On iPhone, check Settings › Battery › Battery Health & Charging. On Android, open Settings › Battery; the names and location of adaptive charging or charge-limit options vary by manufacturer.
4. Try a compatible charger and cable. Use an adapter that supports your device’s charging standard and a cable rated for the needed power. Test a known-good cable and adapter separately so you can see which change affects the result.
5. Check the connection. Make sure plugs fit firmly and inspect the charging port for visible lint or damage. Do not push metal objects into the port. If the connector feels loose or charging starts and stops when it moves, stop using that cable or port until it has been checked.
6. Restart the device and retest. A restart can clear a temporary software issue. Repeat the comparison under similar conditions and at a similar battery level.

When the charger or battery may need service

If charging remains unusually slow well below full with more than one compatible charger and cable, the port or battery may need attention. Check the device maker’s battery-health information if available. A percent-per-minute test cannot measure battery capacity or confirm that a battery is healthy.

Stop charging and seek service if the battery is swollen, the device has a burning smell, or the charging port or plug becomes unusually hot. Do not press a swollen battery or keep testing it. For a device under warranty, contact the manufacturer or seller before paying for a repair.

Why percent per minute changes

Percent per minute is a convenient comparison, but it is not the same as watts. A one-percent increase represents a different amount of stored energy on a small phone than on a large laptop. The displayed percentage is also rounded, and the device may change its charging rate as temperature, battery level, and power use change.

For the clearest comparison, use the same device, start at roughly the same percentage, keep it at a similar temperature, and change only one part of the charging setup at a time.