How to improve the Xiaomi Redmi Note 9: from cleaning to firmware

Xiaomi Redmi Note 9 remains one of the most popular budget smartphones even years after its release. However, over time, many users face brakes, rapid battery discharge and overheating. The reasons are not in the “weak hardware” (the Helio G85 processor and 4 GB of RAM are quite enough for everyday tasks), but in the settings, background activity of applications and features of MIUI. In this article, 10 practical ways to return the smartphone to performance, extend the battery life and correct typical errors without going to the service.

We won’t advise “buy a new phone” or “get over the lags.” Instead, we’ll look at software and hardware methods that actually work, from basic optimization to flashing on MIUI EU or LineageOS. All the instructions are tested on the Redmi Note 9 (models M2003J15SC/M2003J15SS) with current versions of MIUI 12-14 and Android 10-12. If your smartphone “dulls” after the upgrade or just gets old, you’re in the right place.

1. Cleaning the system: remove garbage and cache

The first thing to do with the brakes is to free up the memory from unnecessary files. MIUI actively caches data, and many applications leave behind tails even after they are deleted. On the Redmi Note 9 with 64/128 GB of memory, this is less critical, but on a clogged drive, the system begins to hang.

Start with the built-in Safety Tool → Cleanup:

Run the scan and delete the cache of applications, temporary files and remnants of uninstalled programs.

Pay special attention to the section Deep cleaning - here often hide gigabytes of garbage from messengers and social networks.

Do not delete files manually through Explorer unless you are sure of their purpose: this way you can break the work of system applications.

• 🗑️ Cleaning up the Google Play Services cache: go to Settings → Annexes → Application management → Google Play Services → Memory. → Clear the cache. This will solve the problem of freezing when updating applications.
• 📱 Remove duplicate photos: Use the Google Files app (free in Play Market) and it will find repetitive photos that take up space.
• 🔍 Search for large files: in the same Google Files go to the section Memory Analysis → Big files. Delete unnecessary videos, APK file-book.

⚠️ Note: Do not clear the cache of system applications (e.g. com.miui.home or android.process.media) through TWRP or ADB. This can result in an infinite system load ("bootloop»).

2. Optimization of autoboot and background processes

The Redmi Note 9 suffers from excessive background activity: MIUI by default allows most applications to run in the background, which eats up to 30% of battery power and loads the processor.

Open Settings → Applications → Application Management and for each application:

1. Click on the three dots in the upper right corner → Autostart.

2. disable auto-run for all applications except instant messengers and system services (e.g. Google Play Services).

3. Go back to the list of applications, select the desired → Permissions → Autorun and disable.

• 🔄 Background activity restriction: in the same app settings, select Battery → Background activity and install Restricted for unnecessary programs.
• ⚡ Power saving mode: turn it on in Settings → Battery → Power saving mode. This will limit background synchronization and notifications.
• 📴 Disabling Notifications: Go to Settings → Notifications and disable unnecessary alerts (especially from games and news apps).

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If notifications from messengers have stopped coming after limiting background activity, add them to the exceptions in the battery settings (Settings → Battery → Battery Optimization → All applications).

3. Update of firmware: official and custom options

The Redmi Note 9 slowdown is often due to outdated firmware. Xiaomi regularly releases updates for MIUI, but they don't always come automatically. Check out the current version in Settings → About Phone → MIUI Version. The latest stable version for the Redmi Note 9 is MIUI 14 (based on Android 12).

If the update doesn't come in:

1. Download the latest firmware from the official Xiaomi website (select the Redmi Note 9 model).

2. Move the file to the root of the phone’s memory (not to folders!).

3. Go to Settings → About Phone → System Update, click on three dots → Select a firmware file and specify the downloaded file.

4. Confirm installation and wait for the reboot.

If the official firmware does not suit (a lot of bloatware, advertising), consider custom options:

MIUI EU: Ad-free version, Chinese-based version, installed via TWRP.

LineageOS or Pixel Experience: “pure” Android without a MIUI shell. Requires unlocking the bootloader.

⚠️ Attention: Installing custom firmware voids the warranty and may result in data loss.Before firmware, backup through TWRP or Mi PC Suite.

4. Performance setting: Acceleration and background restriction

Redmi Note 9 processor MediaTek Helio G85 does not support official overclocking, but you can optimize the cores and graphics accelerator Mali-G52.

Without root, the following methods are available:

Enable Performance Mode in Settings → Additional → Performance Mode (not available on all versions of MIUI).

Disable the interface animation: activate Developer Mode (7 times click on the MIUI version in About Phone), then set to the Developer Settings:

- The scale of window animation → Off.

- The scale of the transition animation → Off.

- Duration of the animator → Off.

• 🎮 Optimization for games: in Settings → Special facilities → Play mode Enable Improved Mode and turn off notifications during play.
• 🔧 Process Limitation: In Developer Settings, set Process Limit to Process Maximum 4 (saves RAM).
• 🔋 Turning off thermothrottle: If the phone is too hot, try replacing the thermopaste (see Repair section»).

Set developer mode |Disable interface animation |Limit background processes |Enable performance mode |Elean graphics driver cache-->

5. Extension of battery life: calibration and replacement

The Redmi Note 9 (5020 mAh) battery loses capacity over time, and if the phone runs out in 3-4 hours with moderate use, the problem may be:

Uncalibrated charge controller (incorrect percentage).

Battery wear (more than 500 charging cycles)

- Application background activity (see Section 2).

For calibration:

1. Completely discharge the phone before turning off.

2. Charge up to 100% without interruptions (use the original 22.5W power supply).

3. disconnect from charging and again wait for full discharge.

4. Repeat the cycle 2-3 times.

If the capacity has fallen below 70% (checked in Settings → Battery → Battery status), consider replacing.The original battery for the Redmi Note 9 has an MB-J20BR articulation and costs about 1500-2000 rubles.

- Tweezers and a plastic spatula.

- B-7000 glue to fix the new battery.

Carefulness when disconnecting the plume (it is fragile!).

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If the phone turns off at 20 to 30 percent charge, the problem is with the power controller, not the battery, and that requires a diagnostic in the service.

6. Repair and upgrade: what can be improved physically

If software methods didn't help, the problem may be the hardware.The Redmi Note 9 lets you do a few upgrades yourself:

• 🔧 Replace the thermopaste: Over time, it dries up and the processor starts to overheat (brake when playing or charging). MX-4 kryonaut.
• 💾 MicroSD installation: If internal memory is not enough, use a card UHS-I (Up to 512GB. Format it as an internal drive in Settings → Memory.
• 📶 Replacement of antenna module: if the network signal is missing, check the antenna contacts (they can move away when falling).

To disassemble the phone will need:

- PH00 and Y00 screwdriver set.

- Screen suction cup.

Plastic mediators (so as not to damage the plumes).

⚠️ Note: When changing the screen or battery, do not use a dryer to heat the glue - this will damage the plumes.

7. Solving typical problems: warms, doesn't turn on, doesn't see the SIM

We will analyze the most frequent complaints of owners of Redmi Note 9 and how to resolve them:

If the phone doesn’t respond to the power button, try:

1. Connect to charging for 30 minutes - the battery may have completely drained.

2. Press Power + Volume down for 10 seconds for forced reboot.

3 If it doesn't work, take the phone apart and check if the battery plume has gone.

FAQ: Frequent questions about Redmi Note 9