Why Xiaomi Redmi Note 9 is hot: reasons and what to do

Your Xiaomi Redmi Note 9 has become heated like an iron even with minimal load? This is not always a sign of failure - often the problem lies in software failures or improper operation. But you can not ignore overheating: at temperatures above 45 ° C, the battery degrades 2 times faster, and the processor begins trottling (forced performance loss). In this article, we will analyze all the possible causes of overheating for the Redmi Note 9 - from the banal clog of the charging connector to hidden defects in the motherboard.

The Redmi Note 9 (codename merlin) was released in the 2020 year with a MediaTek Helio G85 processor and a battery on the 5020 mAh. Structurally, it is prone to heating due to:

• 🔥 Dense layout – the processor radiator contacts the battery, enhancing heat transfer.
• 📱 Plastic housing, which is worse at removing heat than metal.
• 🔋 Fast 18W charging, increasing the load on the power controller.

Before you bring your phone to the service, go through our checklist, and in 80% of cases, you can solve the problem yourself in 10 to 30 minutes.

Background processes and “gluttonous” applications

The most common cause of overheating is uncontrolled program activity, and even in standby mode, some applications continue to drain CPU resources, draining the battery and heating the case, especially when it comes to:

• 🎮 Games (Genshin Impact, PUBG Mobile, Call of Duty) can leave processes in the background.
• 📷 Social networks (TikTok, Instagram, Facebook) are constantly synchronizing data.
• 📍 Navigators (Google Maps, Yandex.Maps) – use the GPS and processor even after closing.
• 🔄 Updater (Play Market, MIUI Updater) – download files in the background.

How to check and eliminate:

1. Open Settings → Battery → Battery Use.
2. See which apps consume >5% of their charge in the last 24 hours.
3. Click on the suspicious app → Limit background activity.
4. For games, use Performance Mode in Settings → Special Opportunities → Optimization of games.

Close all games and social networks through "Recently used"

Disable Auto-Update Apps in Play Market

Check the temperature in MIUI Security (cooling section)

Reboot the phone.-->

If Android System or MIUI Daemon is the leader, this is a sign of a system failure. Try resetting to factory settings (more on this below).

2. Charging: Why the phone warms up when connected to the network

The Redmi Note 9 supports fast 18W charging, but not all chargers and cables are compatible.

⚠️ Warning: If the phone only warms when wirelessly charging, that's OK for the Redmi Note 9, as the model is not optimized for the Qi standard. Temperatures can go up to 42-45°C, but that's not critical for the battery.

Original charging Xiaomi|Fast charging from another brand|Wireless charging|From USB-port|Another option-->

3.Overheating due to MIUI updates and firmware

After the MIUI update (especially the large ones, from 12 to 13 or from 13 to 14), many Redmi Note 9 users complain of increased heat.

• 🔄 Background optimization – the system indexes files and configures the cache.
• 🐛 Bugami in firmware — for example, in MIUI 12.5 there was a failure with control of the processor cores.
• 📦 Incorrect installation – if the update is interrupted or downloaded with errors.

How to fix it:

1. Check the current firmware version in Settings → About Phone → MIUI version.
2. If the version is fresh (e.g. MIUI 14.0.4), but the phone is warming up, make a cache reset: 1. Turn off the phone. 2. Press Power + Volume up until the Mi. 3 logo appears. From the Recovery menu, select Wipe Cache → Reboot.
3. If the problem persists, roll back to the stable version via the Mi Flash Tool (instruction below).

⚠️ Warning: Do not install custom firmware (such as LineageOS) on the Redmi Note 9 without unlocking the bootloader.This can cause the device to blink (completely inoperable) due to Anti-Rollback locking.

Hardware causes: from battery to processor

If the phone is warm even in standby mode and the battery goes down in 2-3 hours, the problem may be in the hardware.

1. Battery wear and tear

The average battery life is 300-500 charge cycles (≈2-3 years of active use), and over time, its capacity drops and internal resistance increases, leading to heating.

• 📊 Through the AccuBattery app (showing battery health in percent).
• 🔧 In the engineering menu: dial ##4636## → Battery information.

If you're healthy <50%, you should change the battery, and the original battery for the Redmi Note 9 is about 1500-2000 ₽.

Failure of the power controller

The PMIC (Power Management IC) chip is responsible for power distribution, and when it's damaged, the phone can:

• 🔥 Keep warm even when the screen is off.
• 🔋 Quickly discharge (from 100% to 0% in 1-2 hours).
• 🔌 Do not turn on from charging or require the "correct" position of the cable.

This is a service case, you need to ration or change the board, and the average cost of repair is 3,000-5,000 ₽.

3.CPU overheating due to thermal paste

The Redmi Note 9 uses a liquid metal thermopaste that can dry out or shift over time, leading to:

• 🌡️ Local heating at the top of the phone (where the chipset is located).
• 🎮 Performance drawdowns in games (FPS drops after 10-15 minutes).
• 🔄 Unintentional reboots under load.

The solution is to replace the thermopaste in the service center. Don't try to do it yourself, the risk of damaging the plumes or the chip is very high!

💡

To temporarily reduce the processor’s heat, activate Energy Saving Mode in the battery settings, which will limit the Helio G85 frequency to 1.6 GHz, but reduce heating by 10-15 °C.

5. External factors: covers, sun, humidity

Sometimes the Redmi Note 9 is not warmed by internal problems, but by external conditions.

📱 Cases and stickers

Tight covers (especially silicone or metal inserts) degrade the heat sink. Remove the case and check the temperature in 15 minutes. The difference can be as high as 5-8 °C!

☀️ Direct solar rays

If you leave the phone in the sun (for example, on a torpedo in a car), its temperature can rise to 50-60 ° C. This is dangerous not only for the battery, but also for the screen (the risk of a “burn-in” effect).

💦 Humidity and condensate

If the phone was in high humidity (bath, bath, rain), moisture could get on the board.

• 🔥 Local heating at contact oxidation sites.
• 📵 Network loss or spontaneous reboots.
• 🔋 Quick battery discharge.

Decision:

1. Turn off the phone and remove it. SIM-map.
2. Place it in a silica gel bag (out of a shoe box) for 12 to 24 hours.
3. Do not turn it on until you make sure it is completely dry!

💡

If your phone overheats in the sun, don't turn it on right away. Let it cool to room temperature (20-25°C), or you risk damaging the battery.

6. Viruses and malware

Malware can use the resources of the phone to:

• 💰 Mining cryptocurrency (for example, through a browser).
• 📤 Hidden sending SMS to pay numbers.
• 📍 Data collection (geolocation, contacts, photographs)

Signs of infection:

• 🔥 The phone warms up even in standby mode.
• 📉 Unexplained traffic consumption (check in Settings → SIM-maps and mobile networks → Traffic usage).
• 🔋 The battery goes down in 3-4 hours without active use.

How to check and remove viruses:

1. Install an antivirus (Dr.Web Light or Malwarebytes).
2. Start a deep check (not fast!).
3. Remove suspicious apps (especially those that ask for administrator rights).
4. If the antivirus does not find anything, but the symptoms remain - reset to factory settings.

⚠️ Warning: Don't install antiviruses from unknown developers! Some of them contain malicious code themselves. Use only proven Google Play solutions.

7. When is the time to bring the phone to service

If you’ve tried all of these, but the Redmi Note 9 is still warm, contact the service center.

• 📅 When did the problem start (after falling, updating, getting moisture?).
• 🌡️ In which situations warms up more (when charging, in games, in standby mode).
• 🔧 What you have tried to do (reset, cable replacement, etc.)

Average prices for repairs in Moscow (2026):

⚠️ Warning: If you're offered a replacement motherboard for 10,000-15,000 ₽, consider buying a new phone. For the Redmi Note 9 (2020), it's not cost-effective.

FAQ: Frequent questions about overheating Redmi Note 9