How to turn off fast charging on Xiaomi Redmi Note 9: 3 proven ways

The fast charging feature in the Xiaomi Redmi Note 9 is a convenient option for those who are used to charging a smartphone on the run. However, not all users know that the constant use of accelerated charging can reduce battery life by 15-20% after 1-2 years of active use. If you notice that the battery has become faster to discharge, warm up while charging or swell, it may be worth temporarily or completely disabling fast charging.

In this article, we will discuss three official ways to disable fast charging on the Redmi Note. 9 (including Note models 9 Pro and Note 9S), We'll explain how to check the current charging mode and give you recommendations for optimal battery use. MIUI Allows you to limit the charging current to safe 5V/1A – This is especially true for older devices 2 years.

Why you should turn off fast charging on the Redmi Note 9

Smartphone manufacturers rarely advertise that fast charging accelerates the degradation of lithium-ion batteries, the reason being that high current (from 18W in the Redmi Note 9) heats the battery, which leads to:

• 🔥 Overheating of elements - temperature above 40°C accelerates electrode oxidation.
• ⚡ Increased internal resistance – the battery loses capacity even when stored.
• 📉 Reduce the number of charging cycles – instead of the stated 500-800 cycles, you will get 300-400.

Battery University research shows that charging above 1C (Redmi Note 9’s ~4.5A) reduces battery life by 30 to 50 percent after 1.5 years, especially for devices that charge at night or are connected to the grid continuously (such as power bank mode for other gadgets).

⚠️ Warning: If your Redmi Note 9 swells or starts to shut down when the charge level is above 30%, immediately stop using fast charging.This is a sign of critical battery degradation - further use of accelerated mode can lead to fire.

Another reason to disable the feature is compatibility with non-original charges. Cheap cables or adapters without Quick Charge 3.0 support can damage the smartphone's power controller, which will lead to a break in the USB-C port or motherboard.

How to check if fast charging is enabled on the Redmi Note 9

Before you turn off the function, make sure it is actually active. MIUI has several ways to check:

1. Connect your smartphone to the original charger (18W or 33W for the Note 9 Pro).
2. Pull down the notification bar – if the message “Fast Charge” or “Quick Charge” is displayed, the function is enabled.
3. Open the settings → Battery and look at the charging schedule. With fast charging, the curve will be steep to go up in the first 30 to 40 minutes.

You can also use third-party apps like AccuBattery (available on Google Play), which shows the charging current in real time:

• 🔌 1.5-2.5A – standard charging (5V).
• ⚡ 3And above, fast charging (9V/12V).

If the current exceeds 3A, and the smartphone is warming - this is a direct signal to turn off the accelerated mode.

💡

To get a precise look at the charger model, look at the adapter label. Xiaomi's original chargers are labeled MDY-11-ED (18W) or MDY-12-ED (33W).

Method 1: Disconnect via MIUI settings (official method)

The easiest way is to use built-in options MIUI. However, depending on the firmware version, the path to settings may differ. MIUI 12–14:

1. Open Settings (the gear icon on the main screen).
2. Go to the Battery and Performance section.
3. Select Battery Settings → Charging Mode.
4. Activate the Regular Charging switch (or Standard in some versions).

If there is no charging mode, try an alternative route:

1. Go to Settings. → Additionally.
2. Select Special Opportunities.
3. Find Battery Optimization and turn off Fast Charging.

After applying the changes, connect the charger - the Charging label should appear on the screen without mentioning "fast".

Use the original cable USB-C|Check the battery temperature (should be below 35)°C)|Turn off all apps in the background|Close Resource-intensive Games and Programs-->

Method 2: Use of an engineering menu (for power users)

If you do not have the option to turn off fast charging, you can use the Engineering Mode, which requires caution, as incorrect changes can lead to failures.

Instructions:

1. Open the Phone app and enter the combination: ##4636##.
2. In the menu that appears, select Battery Information.
3. Scroll down and find Fast Charge Config (or Quick Charge).
4. Click on it and select Disable.
5. Reboot your smartphone.

If #4636### doesn’t work, try the alternative code.

##6484## → MTK Engineer Mode → Hardware Testing → Battery

⚠️ Note: In the engineering menu, do not change other options, especially those associated with Voltage or Current Limit. Incorrect settings can disable the power controller, and the smartphone will stop charging at all.

After turning off, check the charging current with AccuBattery – it should drop to 1.5-2A.

Method 3: Current Limitation through ADB (Advanced Method)

For users who are ready to work with Android Debug Bridge (ADB), there is a way to programmatically limit the charging current, which is useful if standard methods do not work or you need to set a custom value (for example, 500 mA for sparing charging).

Step-by-step:

1. Install ADB and Fastboot Tools on your PC (you can download from the official Android Developers website).
2. Turn on USB Debugging on your smartphone: Settings → About Phone → MIUI version (click 7 times to activate Developer Mode), then go back to Settings → Additional → For Developers and enable debugging.
3. Connect Redmi Note 9 to your PC and execute the command in the terminal: Adb devices Make sure that the device is determined.
4. Enter a command to limit current (for example, to 1A): adb shell dumpsys battery set ac 1 Where 1 is current in amperes (you can specify 0.5 for 500mA).

To return the standard settings, use:

adb shell dumpsys battery reset

⚠️ Attention: Teams ADB They're reset when you restart your smartphone, and to make the changes that you make, you have to create an auto-start script or use apps like Tasker to automatically execute commands when you connect to a charger.

What to do if fast charging does not turn off

Sometimes, even after all the manipulations, the Redmi Note 9 continues to charge in an accelerated mode.

• 🔌 Non-original charger – some adapters force Quick Charge activation. USB-PC port (current will not be higher than 0.5A).
• 📱 Firmware failure - update MIUI Up to the latest version or reset settings (Settings) → Resetting settings).
• 🔋 Damaged power controller – if the smartphone warms up even when disconnected fast charging, contact the service center.

If the problem is firmware, you can try to roll back to the old version of MIUI (for example, from 14th to 12th), where the option to turn off fast charging is guaranteed to work. Downgrade instructions are available on the 4PDA or XDA Developers forums.

💡

If the smartphone stopped charging after turning off fast charging through the engineering menu, reset the settings or stitch the device through the Mi Flash Tool.

How to extend the life of the battery after switching off fast charging

Disabling accelerated charging is only part of the battery storage measures, and the following tips will help to maximize the life of the Redmi Note 9 battery:

• 🔄 Avoid full discharge – plug in charging at 20–30% and shut down by 80–90%. Full cycle (0–100%) reduces battery life.
• 🌡️ Control the temperature – do not charge your smartphone at temperatures above 35°C (e.g. in the sun or near heating appliances).
• 📵 Turn it off. 5G/Wi-Fi/Bluetooth At night – background processes heat the processor, which indirectly affects the battery.
• 🔋 Use original accessories – cheap cables and adapters can supply unstable voltage.

To monitor battery status, install AccuBattery or Battery Guru. These apps show:

• Current battery capacity (in mAh).
• The number of full charging cycles.
• Estimate of wear (%).

If the wear has exceeded 30%, consider replacing the battery. For the Redmi Note 9, the original battery costs about 1500-2000 rubles, and replacing it at the service center - another 1000-1500 rubles.

FAQ: Frequent questions about fast charging on the Redmi Note 9