Pick up your phone after it has been on charge for a while and it often feels warm. Most of the time that is completely normal. But if your phone regularly gets hot when charging, it can slow the charge down, wear the battery faster and, in rare cases, point to a faulty phone charger or cable. This guide explains why phones heat up, what you can do about it, and when heat is a sign you should stop and investigate.
Why phones get warm when charging
No charging process is perfectly efficient. Some of the energy going into your phone is always lost as heat, both in the charging circuitry and inside the lithium-ion battery itself. The faster energy goes in, the more heat is produced, which is why fast charging and wireless charging tend to make a phone feel warmer than a slow charge from an old 5W plug.
Modern phones are designed with this in mind. They monitor battery temperature constantly and reduce the charging speed if things get too warm. That is why a phone often charges quickly up to a certain point and then slows down, especially as the battery gets closer to full.
Common causes of a phone getting too hot
1. Using the phone while it charges
Gaming, streaming video, video calls and navigation all make the processor and screen work hard, which generates heat on top of the heat from charging. It is fine to use your phone on charge, but heavy use will make it warmer and slow the charge.
2. A thick case or a soft surface
Phones lose heat through their back and sides. A chunky case, or leaving the phone on a bed, sofa or under a pillow, traps that heat. Charging on a hard, flat surface such as a desk or bedside table makes a noticeable difference.
3. Wireless charging alignment
A wireless charger transfers power between coils in the pad and the phone. If the phone is not sitting in the right spot, more energy is wasted as heat. Metal objects, cards or magnetic mounts between the phone and the pad can also cause heating. A good stand or magnetic charger that holds the phone in position helps; see our wireless chargers for options.
4. Hot surroundings
Charging on a sunny windowsill, on a car dashboard in summer or next to a radiator gives the phone a head start on heat. We cover this in more detail in our guide to charging in cold and hot weather.
5. A poor-quality or damaged charger or cable
Cheap, uncertified chargers may lack proper safety circuitry, and a damaged charging cable can develop resistance at a frayed or bent point. If the plug, the cable end or the charger itself gets hot to the touch, that is a sign of a problem with the accessory rather than the phone.
6. Dirt in the charging port
Pocket lint and dust can stop the plug seating properly, leading to a poor connection. Switch the phone off and gently clear the port with a wooden toothpick or a soft brush, never anything metal.
Simple ways to keep charging cool
- Take off a thick case if the phone regularly feels hot on charge.
- Charge on a hard surface, away from direct sunlight and heaters.
- Avoid gaming or long video calls while fast charging, or accept a slower charge if you do.
- Use a reputable phone charger and cable from a trusted seller. Our wall chargers are a good place to start.
- Turn on your phone’s battery-protection features, such as optimised or adaptive charging, which manage charging overnight.
- Replace any cable that is frayed, kinked or only works at an angle.
Is fast charging to blame?
Fast charging does produce more heat than slow charging, but phones that support it are built to handle it. The phone controls how much power it accepts, and it will slow down automatically if it gets too warm. Using a fast charger with a compatible phone is safe. What matters more is avoiding the extra heat sources listed above, so the phone does not have to cut its charging speed.
When to worry: warning signs
Warm is normal. Too hot to hold comfortably is not. Unplug the charger and stop using it if you notice any of the following:
- The phone is too hot to hold, or shows a temperature warning on screen.
- The charger, plug or cable connector is hot, discoloured or smells of burning.
- The battery appears swollen, the screen is lifting or the back is bulging.
- You hear crackling or see sparks at the socket or port.
If the battery looks swollen, do not keep charging or using the phone. Contact the manufacturer or a reputable repair shop for advice. If the problem seems to be the charger or cable, replace it rather than continuing to use it.
The bottom line
A phone that feels warm on charge is usually just doing its job. Keep it out of the heat, give it room to breathe, go easy on heavy use while fast charging and use a good-quality charger and cable. If heat ever comes with warning signs like swelling or a hot plug, stop and get it checked. When it is time for a replacement, browse our shop for chargers and cables you can rely on.