We are demanding more sophisticated phones – more powerful, with more features and precision – but we also want more compact and lightweight devices. Larger screens require larger batteries. It’s a real challenge for engineers. On top of this complex equation, most smartphones today are certified (IP54, 67…). In other words, they consume more energy and produce more heat but have more difficulty dissipating it because they are more airtight.
What is the maximum temperature our smartphones can withstand?
The answer is not straightforward. For example, Apple states that its “iOS and iPadOS devices are designed to be used in ambient temperatures between 0 and 35°C”. Below and especially above this range, you risk damaging components. Android smartphones have similar thresholds. Oppo, for instance, tests its phones in ovens at 85 degrees for 500 hours. Smartphones can generally withstand temperatures much higher than 35 degrees during their battery tests. However, this extreme heat causes irreparable short and long-term effects.
The effects of heat on your smartphone
In its safety information, Samsung advises not to expose the device to “extreme temperatures as this may damage the device or reduce battery charging capacity and lifespan, along with the battery life.” Indeed, lithium-ion polymer batteries are essentially mini power stations. They produce electricity through chemical reactions. When the temperature rises, the reactive process speeds up – batteries discharge faster.
Manufacturers recommend keeping a battery charged between 20% and 80%. Naturally, a battery will self-discharge. Below 20%, it will wear out prematurely, become unable to hold its charge as well, and need to be charged more often. With high heat, a battery drains much faster and risks mechanically dropping its gauge below the critical 20% mark. So, in the long run, high temperatures combined with more charge cycles will cause premature battery death.
The screen is the second most fragile smartphone component when exposed to heat and sunlight. Whether switched off or on standby, its panel is black and absorbs maximum light rays. A screen consists of a glass layer that dissipates heat very poorly. Right underneath is an extreme concentration of electronic components, which contain metal that will expand with higher temperatures. Due to their small size, these components can easily damage adjacent components.
What not to do in hot weather:
Do not update Android or iOS, and do not download or install software in general. An update in a hot environment harms your smartphone in two ways. First, it makes huge demands on the WiFi/4G/5G communication chip and processor to enable high-speed downloading. Then, installing large amounts of data (hundreds of megabytes) will monopolize the processor for several minutes. Finally, the battery will discharge quickly and heat up even more when it’s already running hot.
Do not restore from another phone or the cloud. Just like installing an update, restoring or initializing a phone from a cloud backup or another phone is strongly discouraged. Consecutively installing software or large amounts of data in a short timeframe will hog the CPU and worsen battery temperature.
Do not use the 5G network. Downloading heavy content (hundreds of megabytes) is already discouraged. With a 5G chip, it’s even worse. 5G is 10 times faster than 4G, but its chip is not 10 times more power efficient – on the contrary, a 5G chip will drain your battery faster when heat is high.
Do not charge your smartphone. As you must have noticed already – charging a phone produces heat, both in the battery and the charger. During charging, the chemical reactions intensify over a short timeframe, generating heat. Fortunately, most manufacturers implement safe charging like OnePlus and Xiaomi. Like any device in operation, the charger also heats up.
Do not use a fast charger. Fast (30, 60, 100W, or more) and ultra-fast charging causes the same problems as normal charging but multiplied. Already under normal conditions, fast charging generates additional heat. By reducing the charging time, the battery’s internal temperature increases. It goes without saying that a bad cable (incompatible with fast charging or damaged) will disrupt charging and possibly cause power surges or even fires.
Do not wirelessly charge. We already know that wireless charging reduces a smartphone’s lifespan. But inductive charging also significantly increases device temperature. This heat comes from the energy lost between the phone and the wireless charger. “The heat generated is therefore transferred to the smartphone by simple thermal conduction and convection,” according to researchers from the University of Warwick (UK).
Do not use a protective case that prevents heat dissipation. Any type of case, regardless of material, will reduce the smartphone’s ability to dissipate its internal temperature. Of course, the thicker the case, the more insulating it will be, preventing the phone from cooling down to an acceptable level.
Do not watch streaming videos or download heavy content. Like installing an update or restoring a backup, streaming videos from a platform (YouTube, Amazon Prime, Netflix, etc.) require much power, especially in high definition. Same for downloading large files. The main CPU for downloading and GPU for streaming is a double whammy.
Do not play graphics-intensive games. Games like Genshin Impact require sustained CPU, GPU, RAM, and storage. Additionally, the screen refresh rate doubles, therefore consuming twice as much power.
Limit the use of the most energy-hungry apps. Some apps exchange a lot of data with servers and use up a lot of energy. The main offenders are communication apps, social networks, and geolocation services – Google, Facebook, Messenger, WhatsApp, Amazon Alexa, Gmail, Uber, Waze, Google Chrome, YouTube Music, Instagram, Telegram, Twitter, TikTok, Amazon Shopping.
Do not put a hot phone in the fridge or freezer. As mentioned before, electronic components expand with heat and will contract too quickly in a fridge or freezer’s cold and humid environment. This can damage the smartphone, even if it is IP67-rated.
What to do in case of high heat:
Place your smartphone on a flat, lint-free, ideally cold surface. This allows the phone to dissipate heat as quickly as possible. Do not place on hot surfaces like metal or stone that absorb and retain heat from the sun.
Have the battery repaired (and/or replaced). A battery worn out by too many charge cycles, especially bad ones, will discharge faster when overheated.
Prefer standard HD over 4K/UHD for videos. 4K (3840×2160 pixels) consumes almost 4 times more power than HD (1920×1080 pixels). It’s even worse with modern codecs like HEVC/H265.
Remove malware and other viruses. Using an antivirus and uninstalling unneeded software will limit CPU and memory use, preserving the battery.
Close background apps. They use phone resources (RAM, CPU, storage, GPS, etc) when not in use.
Disable notifications. They continuously consume energy by communicating with servers.
Limit Android power usage via settings > battery > turn on low power mode
Switch on airplane mode. Cutting off-network access suspends power drainage. The phone should start cooling down.
Prioritize 4G over 5G. As 4G speed is much lower than 5G, the smartphone will tend to heat up less than when using 5G.
Avoid uncertified chargers and cables. An overpowered charger can damage the battery. It may also lack an original charger’s safety features (electronic and software). An undersized cable, especially for fast charging, can cause overheating issues for both the charger and the phone.
Apple’s advice (also valid for Android phones):
“[Avoid] leaving your device in a car on a hot day. The inside of a car can become extremely hot – like a sauna. In just one hour, the temperature in a car can climb from 60°F to over 80°F! From white to black cars, it can rise even more. The iPhone will be unable to cool down. This is especially dangerous if the device is charging.”
“[Avoid] Leaving your device in direct sunlight for an extended period of time.” The sun’s UVA and UVB rays can damage the screen, battery, and internal components. A simple sheet of paper on the screen can reduce heat absorption and protect your iPhone.
“[Avoid] using certain features in hot conditions or direct sunlight for a long time, like GPS tracking or navigation in a car, graphics-intensive gaming, or AR apps.” After gaming, real-time geolocation on an iPhone (Google Maps, other navigation apps) strains the battery and screen.