What to do if the brakes and lags Xiaomi Redmi Note 9: a step-by-step guide

Your Xiaomi Redmi Note 9 is slow to work, apps take a long time to open, and animation twitches? This is a common problem, especially after 1-2 years of use. The reasons can be either software (cumulative memory, outdated firmware) or hardware (battery wear, overheating). In this article, we will discuss all possible ways to eliminate lags, from simple to radical.

The Redmi Note 9 (codenamed merlin) came out in 2020 with a MediaTek Helio G85 processor, 3/4/6 GB of RAM and MIUI based on Android 10. Over time, even such “average” begin to slow down due to accumulated debris, background activity of applications and system updates. The key feature of this model is the tendency to overheat at high load, which immediately affects performance.

Before you bring your phone to service, try the solutions in this article, and we've put them from the fastest and safest to the most complex. Let's start with the diagnostics!

1.Diagnosis: Why does the Redmi Note 9 lag?

The first step is to determine what exactly causes the brakes, and here are the main symptoms and their possible causes:

• 🔄 Applications are long to open or fly out → Lack of RAM (RAM) or garbage in the cache.
• 🔥 The phone is warming and slowing down. → CPU overload, background processes or battery problems.
• 📉 Lags when scrolling the menu MIUI → Outdated firmware or failures in the shell.
• 🎮 Slowdowns in games → Trottling the processor due to overheating or weak optimization.
• 🔋 Brakes with low battery charge → Battery wear or activation of energy saving mode.

To more accurately identify the problem, check:

1. Go to Settings → About Phone → MIUI version and make sure the firmware is up to date.
2. Open Settings → Battery → Battery Use – See which apps use up the most power.
3. Install the CPU Monitor or AIDA64 app to monitor CPU load and temperature.

If you start to lay down after a drop or moisture, the problem is more hardware, you need a diagnostic in the service center, and software optimization will help in all other cases.

2. Cleaning up memory and cache: quick ways

Let's start with the simplest methods that don't require resetting or flashing, and most often, lags are caused by overflowing memory or clogged cache.

Cleaning up the app cache

Cache speeds up programs, but it accumulates over time and can cause malfunctions.

1. Go to Settings → Applications → Application Management.
2. Choose an app (start with the frequently used ones: Facebook, Instagram, Chrome).
3. Press Warehouse. → Clear the cache.

Cleaning the system cache

For deep cleaning:

1. Turn off the phone.
2. Press the Power button + Volume up to enter Recovery Mode.
3. Select Wipe & Reset → Wipe Cache (use volume buttons for navigation).
4. Confirm the action and restart the phone.

If the lags remain after cleaning the cache, proceed to the next step - MIUI optimization.

3. MIUI Optimization: Disabling Unnecessary Functions

MIUI shell is known for its functionality, but many chips are in the background and eat resources.

Disabling animation and visual effects

Reducing animations will speed up transitions between screens:

1. Activate Developer Mode: Settings → About Phone → MIUI version (click 7 times).
2. Back to Settings → Additionally. → For developers.
3. Find the items: Window animation scale → Choose No animation. Size of transition animation → No animation. Duration of animation → Off..

Disabling Auto-Run Applications

Many programs run automatically and hang in the background to prevent this:

1. Go to Settings → Applications → Application Management → Autorun.
2. Turn off auto-run for unnecessary apps (especially instant messengers and social networks).

Set-up of performance mode

MIUI has a hidden mode to improve performance:

1. Open the settings → Battery → Battery mode.
2. Select Performance (if there is no such item, turn on Developer Mode and find MIUI Optimization).

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If the interface becomes too sharp after disabling the animation, return the animation scale to 0.5x – this is a compromise between smoothness and speed.

These settings will reduce the workload on the processor and RAM, but will not solve the problem radically if the phone is severely outdated or clogged with garbage.

4. Update firmware and reset settings

Outdated firmware is one of the main reasons for lags. Xiaomi regularly releases updates for the Redmi Note 9, fixing bugs and optimizing performance.

How to update MIUI

Check the relevance of the version:

1. Go to Settings → About the phone → System update.
2. Click Update Checker.
3. If a new version is available, download and install it (preferably via Wi-Fi).

If the upgrade doesn't work or doesn't, try resetting to factory settings.It's a radical method, but it often solves lag problems.

How to Reset (Hard Reset)

⚠️ Warning: Reset will delete all data from your phone! pre-backup to Settings → Additionally. → Backup and reset.

1. Go to Settings → Additional → Backup and Reset → Reset settings.
2. Select Reset all settings and confirm the action.
3. After restarting, set your phone as new.

If the reset didn't work, the problem might be the firmware, in which case it's worth considering flashing through Fastboot or Recovery, but that's a topic for a separate article.

5. Checking hardware problems

If the software methods failed, the lags could be caused by hardware malfunctions.

To diagnose hardware problems:

1. Check the status of the battery through the application AccuBattery (capacity below 80% - critical).
2. Check the charging connector for oxidation or damage.
3. If the phone fell, check the integrity of the screen and plumes (extraneous pixels, artifacts are a sign of problems).

⚠️ Warning: If the phone is warmed to 50°C and above in simple (checked in the AIDA64), Do not use it before repairs – it can damage the motherboard.

Hardware repair is better to entrust the service center, especially if it is a question of replacing the battery or cleaning from dust (in Redmi Note 9, the body is indissoluble).

6 Radical methods: custom firmware and iron replacement

If neither of these methods worked, there are two options:

1. Install custom firmware (for example, LineageOS or Pixel Experience).
2. Iron upgrade (replacement of the battery, increase of memory).

For custom firmware installation:

1. Unlock the bootloader through the Mi Unlock Tool (requires a Xiaomi account).
2. Install TWRP Recovery.
3. Sweep through the selected firmware (see instructions in the 4PDA or XDA Developers forum).

Upgrade of iron

The following upgrades are available for Redmi Note 9:

• 🔋 Replacement of the battery with a new (original) MN-BM4X or equivalent capacity of 5020 mAh).
• 💾 Installation of a class microSD card A2 for porting applications (through Settings) → Warehouse → Internal memory. → Transfer data).
• 🔧 Cleaning from dust and replacing thermopaste (relevant in case of constant overheating).

The cost of replacing the battery in the service is from 1500 to 3000 rubles (depending on the region). Self-replacement is possible, but requires care (risk of damage to the battery plume).

7. Alternative solutions: if nothing helps

If the Redmi Note 9 continues to lag even after all the manipulations, consider the following options:

• 📱 Use as a second phone for calls, instant messengers and non-resource-intensive tasks.
• 🎮 Turning into a game console – install emulators (RetroArch, PPSSPP) And plug in the gamepad.
• 📺 Home Media Player – Connect to your TV via Miracast or HDMI-adapter.
• 💰 Sale / exchange for a new model - Redmi Note 9 can still be profitable to pass in trade-in (for example, on Poco). X5 or Redmi Note 12).

If you are selling your phone, first:

1. Make a full reset (Settings → Additional → Backup and Reset).
2. Delete your Mi Account (otherwise, the new owner will not be able to use the phone).
3. Check the operability of all modules (camera, speakers, microphone).

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Before selling, be sure to untie the phone from your Xiaomi account via Settings → Xiaomi Account → Sign out. Otherwise, the buyer will not be able to activate the device!

FAQ: Frequent questions about lags on Redmi Note 9

If after all the manipulations Redmi Note 9 continues to slow down, most likely, it is hardware wear, in which case it is worth thinking about replacing the phone – modern applications and games require more resources, and even optimization will not return to its former smoothness.