Why the battery is quickly discharged on Xiaomi Redmi Note 9: a full analysis of the causes and solutions

Introduction: real numbers of the Redmi Note 9

Owners of Xiaomi Redmi Note 9 often face the problem when the battery at 5020 mAh discharges in 4-6 hours of active use instead of the declared 10-12. According to the tests GSMArena (2020), when playing video with a screen at 50% brightness, the smartphone should keep a charge of up to 17 hours, but in practice many users get 2-3 times less. The gap between laboratory tests and real operation is often associated not with battery failure, but with system settings, background processes and battery wear.

In this article, we will discuss 12 key causes of rapid discharge, including hidden MIUI features, hardware problems and user errors. You will learn how to diagnose a problem using the built-in Settings → Battery tools, which applications eat up charge in the background, and when it is time to change the battery.

Battery wear: how to check the real capacity

Redmi Note 9 lithium polymer batteries lose up to 20% of their capacity after 500 charging cycles (approximately 1.5-2 years of active use). If your smartphone is older than 2021, the problem may lie in the degradation of the elements.

• 📊 Enter the phone code ##4636 in the app## → Select "Battery Information." Level will show current charge and health status (below 80% critical).
• 🔋 Use the AccuBattery app (Play Market) and after 3-5 charging cycles, it will show the actual capacity, for example, if you display 3,800 mAh instead of 5020 mAh, the battery is worn out by 25 mAh%.
• ⚡ Connect your smartphone to charge and watch the charge rate. If the charge is at 0-20%, it is at a speed of less than 1000 mA (checked by AccuBattery), this is a sign of wear and tear.

The average life of the original Redmi Note 9 battery is 3-4 years. If the capacity has fallen below 60%, it will cost 1500-2500 rubles (depending on the service).

2. Background processes and "gluttonous" applications

MIUI (especially versions 12-14) aggressively optimizes background tasks, but some apps get around these limitations, such as Facebook, TikTok and messengers like Telegram or WhatsApp can use up to 30% of the charge per day even in standby mode.

1. Open Settings → Battery → Battery Use.
2. Click on the three dots in the upper right corner and select "Show System Consumption."
3. Look at apps marked “Background Use” – if it’s more than 10%, it’s an anomaly.

Top.-5 «Power-intensive applications for Redmi Note 9 (data XDA Developers):

Disable auto-start for unnecessary applications |

Prohibit background activity in battery settings|

Update all applications to the latest versions|

Remove “cleaners” and optimizers

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⚠️ Note: If you see a mediaserver or Android.system process with a consumption of more than 15% in the battery consumption list, this may indicate a virus or malfunction. MIUI. Do a check through Google Play Protect or reset the settings to the factory.

3. MIUI settings that "eat" charge

MIUI by default includes a number of features that are good for marketing but bad for the battery, such as Smart Recommendation (shown ads in the app menu) or Second Space (duplicates processes).

• 🔍 Settings → Privacy → Special permits → Smart recommendation → turn off.
• 📱 Settings → Second space → remove if you do not use it.
• 🌐 Settings → Connections and sharing → Transfer of data → Turn off automatic synchronization.
• 📡 Settings → SIM-maps and mobile networks → Mobile data → turn off 4G+, If you don’t need high-speed internet.

Another hidden feature is Automatic Brightness MIUI, which, unlike standard Android, uses additional sensors and algorithms that increase battery consumption by 5 to 7 percent, and replace it with manual adjustment or install the Lux Auto Brightness app.

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If after disabling the Smart Recommendations in the application menu there are empty places, restart the phone - this will reset the launcher's cache.

4.Iron problems: from display to communication module

Hardware malfunctions can reduce battery life by 2-3 times. Common causes include:

• 📱 Display: Illumination matrix Redmi Note 9 (IPS LCD) It consumes up to 40 percent of the charge at maximum brightness, and if the screen flickers or changes brightness spontaneously, it's a sign that the plume or controller is malfunctioning.
• 📶 Communication module: A weak network signal (1-2 divisions) makes the modem work at the power limit. → SIM-map → Network signal.
• 🔊 Dynamic/vibration: Constant vibration at notifications or loud noise in games increases consumption by 5-10%.
• 🌡️ Overheating: If the body is heated above 40°C (checked in CPU Monitor, the protection is triggered, and the battery discharges faster.

For the diagnosis of iron:

1. Install the Throttling Test (Play Market) CPU to see if the processor is limiting its power due to overheating.
2. Check Settings → About Phone → MIUI version and click on “Kernel Version” several times. If the Hardware Info menu appears, it will contain information about the temperature and voltage of the battery.

⚠️ If the phone is running 10-15% per night in airplane mode, the problem is almost certainly in the power controller (chip). PMIC). Its replacement costs 3000-50,000 rubles, but without it, the battery will degrade 2 times faster.

5. Charging errors: what kills the battery in 6 months

Many Redmi Note 9 users are unaware that improper charging reduces battery life by 30-40%.

• ⚡ Use of non-original chargers (especially with output current) >2.4A). They can supply unstable voltage, which leads to battery bloating.
• 🔌 Charging to 100% and storage to full charge. Optimal range is 20–80%.
• 🌡️ Charging at temperatures above 30°C (e.g., in the sun or during games) This accelerates the degradation of lithium polymer elements.
• 📵 Using the phone while charging for resource-intensive tasks (games, video editing).

How to charge correctly:

6.Viruses, Mining and Hidden Threats

Redmi Note 9 based on MIUI is vulnerable to hidden mining (especially if APKs are installed from unverified sources).

• 📈 Unexplained battery consumption (e.g. 50% in 2 hours on standby).
• 🔥 Overheating of the body even without load.
• 📊 B Settings → Battery visible com.android.system process with high consumption.

How to check and delete:

1. Install Malwarebytes or Dr.Web Light and perform a deep scan.
2. Check the list of installed apps in Settings → Apps. Delete suspicious ones (for example, with names like System Update, Flash Player).
3. Open Settings → Special Features → Special Features Services and remove unknown services.

⚠️ Warning: If the phone still discharges quickly after removing viruses, check DNS-Some malware changes them to its own, which leads to traffic leakage and additional battery consumption.

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Even official apps from the Play Market may contain hidden mining modules, such as Google removed more than 200 apps with miners in 2023, including “battery optimizers” and “launchers.”

7 MIUI Updates: Why New Versions Are Eating Up Battery

Each major MIUI upgrade (e.g. 12 to 13) brings not only new features but also hidden processes that increase charge consumption. For example, MIUI 14 introduced a feature called Smart Segmentation (for the camera) that works in the background to roll back changes or optimize the system:

• 🔄 Reverse to the previous version through Settings → The phone. → Updating the system → Three points. → Select the update package (needs a firmware file).
• ⚙️ Turn off automatic update downloads in Settings → The phone. → Updating the system → Settings (cogs).
• 📵 If after the update there are lags, perform a cache reset: turn off the phone, press Volume up. + Meals, select Wipe Cache.

Compare battery consumption on Redmi Note 9 in different versions of MIUI (XDA test):

FAQ: Frequent questions about the Redmi Note battery 9