What causes a phone to overheat?

There are several potential causes for a phone overheating. The most common reasons phones overheat include processor-intensive tasks like gaming or streaming videos, direct sunlight exposure, faulty battery, and malware/viruses.

Table of Contents

Quick Summary of Main Causes

Here is a quick overview of the main causes of phone overheating:

Using processor-intensive apps like games, videos, or navigation

Charging with a faulty or damaged charger
Excessive brightness or using GPS/Bluetooth simultaneously
Direct sunlight exposure for a prolonged time

Installing apps that run constantly in the background
Outdated software and operating system
Too many tabs open in the internet browser

Malware, viruses, or software bugs
Damaged or swollen battery
Accumulation of dust and debris inside the phone

Processor-Intensive Tasks

One of the most common reasons a smartphone may get hot is from running processor-intensive apps and tasks. Smartphone processors have to work extra hard to power things like:

3D gaming apps
Augmented reality apps

Video streaming services
Video calling
Multi-tasking between many open apps

Recording 4K video
Using GPS navigation

Activities like these can quickly make the processor run at full capacity as it renders graphics, processes image data, and runs complex calculations. This spike in workload generates more heat. Gaming for long periods is especially taxing as the processor has to constantly draw power to run the game software and graphics. The battery also drains faster.

Why Processor-Intensive Tasks Cause Overheating

Modern smartphone processors like the Snapdragon 865 and Apple A13 Bionic are incredibly powerful, but also produce significant heat. Here’s why:

More transistors packed together – Newer processors have billions of tiny transistors squeezed together onto a small chip. This generates heat as electrical currents pass through the components.
Higher clock speeds – Faster processors mean the transistors switch on and off at higher frequencies. Higher clock speeds equate to more heat.

Power draw – Powerful chips need more electricity to run. Drawing more power inevitably creates excess heat that must be dissipated.

Combining strenuous tasks with an advanced high-speed processor in a compact phone body is a recipe for elevated temperatures. The heat is contained within the chassis rather than dispersing over a larger surface area like a laptop or desktop computer.

Charging with Faulty or Damaged Chargers

Using damaged, broken, or incompatible phone chargers can also cause overheating problems while powering up your device. Things to watch out for include:

Bent/damaged charging cable – A wire that is crimped or bent improperly can interfere with smooth power transmission and generate excess heat in the faulty spot.
Cable wire exposed – If the protective rubber coating on a charging cable frays and exposes the inner wires, it can create a fire hazard and cause the phone to heat up.
Using generic/cheap replacements – Low quality aftermarket cables often don’t have proper voltage regulation. Too much or too little power flow overheats the battery.

Wall adapter failures – Faulty adapters can deliver inconsistent power that confuses the phone’s charging circuits.
Incompatible chargers – Using a charger with incorrect voltage/amperage ratings for your specific phone model can lead to overheating.

Avoid third-party $2 cables and generic chargers. Use only manufacturer-approved charging accessories compatible with your phone.

Signs of a Faulty Charger

Watch for these signs that indicate a defective or damaged charger:

Phone gets hot when plugged in
Charging is intermittent (stops and starts)

Charging port is hot to the touch
Charging is very slow
Wall adapter becomes warm

Melted plastic on charger or port
Burning smell from phone or charger
Discoloration on charging port

Frequent electric shocks when using charger

A charger exhibiting any of these issues should be replaced immediately before it causes damage to your phone or presents a fire risk.

Excessive Brightness and Background Activity

In addition to processor-heavy apps, other activities that generate extra heat include:

High screen brightness – The brighter the display, the more battery power and processor resources required. This heats up the phone components.
GPS navigation – Using GPS and maps frequently requires significant processor power. The phone also can’t sleep/cool down during navigation.
Bluetooth and WiFi – Having these antennas active uses more energy. Combining them with other tasks makes the phone work harder.

Poor signal areas – Seeking a signal draws much more battery and processing as the phone repeatedly scans for connectivity.
Many background apps – Too many apps running constant background tasks can keep the processor perpetually busy and warm.

Try to minimize these activities when your phone feels warm. Turn down screen brightness, close some apps, disable Bluetooth/GPS when not needed, and avoid areas with poor reception.

Direct Sunlight Exposure

Leaving your phone directly exposed to the sun on a hot day can cause it to warm up excessively. The greenhouse effect plays a role here. Follow these tips:

Never leave your phone in a closed car on a sunny day. Temperatures inside a car can soar dangerously high.
Avoid leaving the phone in direct sunlight for prolonged periods of time. The exterior surface and internal components heat up.

Consider using a reflective phone case or attaching sun shades if leaving the phone in sunlight is unavoidable.
Place the phone in a bag or purse rather than exposed if you must have it in the sun.
Try to limit sun exposure to 15-20 minutes at a time. Take frequent breaks in the shade.

The ambient air temperature also impacts how hot the phone gets in the sun. 95°F (35°C) air heats a phone more than 65°F (18°C) air at the same sun exposure.

Why Sunlight Overheats Phones

Here are the key reasons direct sunlight causes phones to overheat:

The sun warms the exterior surface – Direct infrared radiation is absorbed by the phone’s outer materials after penetrating the glass/plastic.

Greenhouse effect traps heat inside – The heated outer surface and internal components then heat the air inside the chassis.
Dark colors absorb more light – Darker phone colors like black tend to get hotter in the sun than white or reflective colors.
Battery generates extra heat – Power draw increases to maintain brighter screen visibility in sunlight.

Circulation is limited – Still air and a compact chassis prevent efficient heat dissipation.

For these reasons, sunlight is one of the biggest triggers for phone overheating. Keep your device shaded as much as possible on hot sunny days.

Malware, Viruses, and Software Bugs

Malware, viruses, and unoptimized software can also cause phone overheating in some cases. Here’s how:

Malware uses processor resources in background – Malicious apps infect phones to mine cryptocurrency, overload the processor, or transmit/encrypt data.
Viruses hog system resources – Viruses replicate themselves and spread through a phone’s storage and memory consuming extra power.
Software bugs – Glitches, memory leaks, and coding errors in apps can trigger excessive CPU usage and power draw.

Constant wakelocks – Rogue apps abuse wakelocks to keep the phone awake and hot.
Spammy notifications – Frequent useless notifications keep the display, modem, and processor active.

Use trusted anti-malware apps, avoid sideloading random files, and only install apps from reputable sources like Google Play Store to minimize risks.

Signs of Malware Causing Overheating

Watch for these signs that malware or a virus may be contributing to phone overheating:

Sudden spike in battery drain
Laggy, sluggish performance

Unexpected increase in data usage
Pop-up ads and weird notifications
Unfamiliar apps installed on your phone

Higher than normal memory/CPU usage
Phone is warm despite no recent use

Run a security scan using a trusted anti-virus app if your phone shows these symptoms. It could identify and remove any malware or threats.

Damaged or Swollen Battery

Lithium-ion batteries can become damaged and swollen as they chemically age or are exposed to excessive heat cycles. A bulging battery strains against the phone’s chassis and is prone to overheating. Signs include:

Visible swelling/bloating of the battery through the phone’s casing
Phone chassis Won’t properly close or becomes warped/bent

Overheating even when phone use is light
Faster than normal battery drain
Slow or uneven charging

A swollen lithium-ion battery is dangerous and can catch fire. Stop using the phone immediately and replace the battery if you observe any of these issues.

Why Swollen Batteries Overheat

Swelling is caused by chemical reactions within the battery cells. Here are some reasons it happens:

Age-related degradation – Older batteries naturally lose elasticity in materials over years of use.

Overcharging and over-discharging – Exceeding voltage limits strains battery components.
High temperatures – Heat accelerates chemical aging reactions inside the cell.
Internal shorts – Damaged separators allow short circuits between electrodes.

Extreme cold – Freezing leads to metallic lithium plating on electrodes.

Once swelling begins, the battery is permanently damaged. Gases released during abnormal chemical reactions increase internal pressure, forcing it to bloat outward.

Accumulation of Debris and Dust

Dust, pet hair, crumbs, and other fine particulate that enter a phone’s ports and openings can accumulate inside over time. This debris eventually clogs ventilation pathways and heat sinks, causing overheating issues. Symptoms include:

Visible dust/debris around charging port, headphone jack, speakers, etc
Muffled or lower speaker volume as dust blocks openings
Gradual overheating that worsens over time

Sluggish charging as port gets clogged

Carefully clean visible debris from all phone openings using compressed air, isopropyl alcohol, and soft brush tips. Avoid moisture buildup. Periodic cleaning helps prevent accumulated material inside the chassis from causing problems.

How Does Internal Dust Cause Overheating?

Buildup of particulate inside the phone interferes with cooling in a few ways:

Blocks airflow – Prevents natural convection of hot air out and cool air in.
Insulates hot components – Traps heat near heat sources instead of dissipating it.
Clogs fan ventilation – Stops internal cooling fans (if present) from working.

Traps moisture – Absorbs humidity and makes cooling less efficient.

Good ventilation is critical for controlling temperatures inside an electronic device. Letting dust accumulate over time can eventually lead to thermal issues.

Preventing Phone Overheating

Use the following proactive tips to avoid phones overheating in daily use:

Don’t expose phone to direct sunlight for very long when outdoors.
Don’t leave phone charging inside a closed car on a hot day.
Avoid processor-intensive apps for long periods, give phone breaks to cool down.

Check for swollen/bulging battery, replace it immediately if found.
Use manufacturer-approved original chargers and cables to avoid issues.
Update your phone operating system and apps to latest stable versions.

Check for malware and viruses if phone shows unusual battery/CPU usage.
Clear phone ventilation openings of dust regularly with compressed air.
Turn down screen brightness when in hot environments.

Disable GPS/Bluetooth when not actively in use.

Following sensible usage and maintenance habits helps keep your phone running cooler for longer.

What to Do if Your Phone Overheats

If you notice your phone getting excessively warm or hot during use, follow these steps:

Stop using the phone immediately if it feels very hot, turn it off, and let it cool down.
Avoid direct sun exposure and don’t charge until it cools down.
Remove protective case to prevent trapping heat.

Check if any apps are overusing CPU or battery in overheating duration.
Update software, restart phone, close background apps to see if it helps.
Backup data and factory reset if other steps don’t fix overheating issue.

Replace battery if it appears swollen/damaged.
Contact manufacturer if overheating persists after troubleshooting.

Severe or sustained overheating can permanently damage phone components. So act promptly to mitigate the problem.

Conclusion

Phone overheating usually results from processor-intensive activities, faulty chargers, sun exposure, malware, or a degraded battery. Good usage habits can prevent many issues. Act quickly if overheating occurs by shutting down the phone and troubleshooting the possible cause. With diligent maintenance and responsible use, you can extend your phone’s lifespan and performance.