Why does a charger slow down when a device gets hot?

Your phone or laptop starts charging quickly, then the rate drops after the device warms up. It can seem like the charger or cable is failing, but devices often reduce charging speed to manage heat and protect the battery.

Compare the charging rate under consistent conditions before replacing anything. The Charger & Cable Test measures the change in battery percentage per minute, so you can check whether heat, a cable, or a charger makes a difference.

Compare charging rates

1. Open the Charger & Cable Test on the device you want to check. The tool appears only if your browser reports battery information, which is more common on laptops, tablets, and phones.
2. Connect the charger and cable you normally use. Keep the device in the same place, and note the battery percentage and whether the device feels warm.
3. Let the test measure the charging rate in percent per minute. Avoid using demanding apps while it runs, because their power use can affect the result.
4. Repeat under similar conditions with another compatible cable or charger, if you have one. Compare the results at roughly the same battery percentage, with the screen and apps in a similar state.

A single reading is not a verdict. Charging speed naturally changes as the battery fills, and a browser test estimates the rate from battery data. It does not measure the adapter's electrical output or read the device's internal temperature.

What the result means

The rate drops as the device gets warm

This is often normal temperature management. The device controls how much power reaches the battery, and may reduce charging speed when the battery or other components get hot. The charger itself may not have changed. Let the device cool naturally, then compare again under the same conditions.

Both chargers slow down when the device is hot

That points more toward the device limiting charging than toward one faulty adapter. Heavy use, direct sunlight, a warm room, or a thick case can add heat. If the device shows a temperature warning, follow its on-screen instructions and stop charging until it is safe to resume.

One cable or charger is consistently slower

The accessory may not support the same charging standard or power level as the other one. A worn cable, loose connector, or unsuitable adapter can also limit charging. Use accessories compatible with your device, and compare them at similar battery levels and temperatures.

The rate is low with every setup, even when cool

Check whether the device is running a heavy task, whether the charging port is dirty or loose, and whether the battery is already near full. If charging remains unusually slow with a known compatible charger and cable, the port, battery, or charging circuit may need service.

How to reduce heat and check the cause

1. Pause demanding tasks. Games, video recording, navigation, large downloads, and video calls can make a device use power while it charges. Close or pause them, turn off the screen, and give the device time to cool.
2. Move it to a cooler, shaded spot. Keep the device out of direct sun and away from heaters or hot car interiors. Place it on a hard, open surface rather than on bedding or inside a bag. Let it cool at room temperature. Do not put it in a refrigerator or freezer.
3. Remove a heat-trapping case. If the case is easy to remove and the device is not dangerously hot, take it off while charging. Make sure the cable remains firmly connected and that the port is not under strain.
4. Check which apps are using power. On Windows 11, open Settings › System › Power & battery and review battery usage. On macOS, open System Settings › Battery. On Android, look under Settings › Battery › Battery usage; names can vary by manufacturer. On iPhone, open Settings › Battery. Close apps doing unusually heavy work, then retest.
5. Try a compatible cable and adapter. Check the cable for fraying, bent connectors, or a loose fit. Test one change at a time, and use a charger that meets the device maker's requirements. A higher power rating alone does not guarantee faster charging, because the device and cable must support the same charging method.
6. Restart the device if the slowdown persists. A restart can stop a stuck task from keeping the processor busy. Once the device is cool, reconnect the charger and compare again.

When the device or charger needs attention

Stop using a charger or cable that is damaged, smells burnt, sparks, or becomes unusually hot. Do not open an adapter or try to repair its wiring. If the device repeatedly displays a temperature warning, becomes too hot to handle, or stops charging with several compatible accessories, unplug it if safe and contact the manufacturer or a repair shop. A swollen battery needs prompt professional attention, not another charging test.

Why charging slows even without a problem

Charging is usually fastest when the battery is low and the device is cool. As the battery approaches full, its charging system reduces the rate. Heat can make it reduce the rate sooner. The percentage-per-minute result is therefore useful for comparing setups, but it is not a fixed speed rating for your charger.

Battery information depends on what the device and browser expose, so the test cannot diagnose battery health or confirm a charger's wattage. Compare like with like, and treat persistent heat or a warning message as more important than a single rate reading.