Xiaomi Mi 9 is the flagship smartphone of 2019, which is still popular thanks to the powerful hardware and support for current firmware. However, its Quick Charge 4+ (27 watts) fast charging feature is not always useful: it accelerates battery wear, causes overheating and can reduce battery life by 15-20% during heavy use. If you notice that the phone warms up while charging, the battery quickly discharges or you just want to extend its life, turning off accelerated charging will be a smart decision.
In this article, we will discuss all the working ways to disable fast charging on the Mi 9 (including global, Chinese and custom firmware), explain how this will affect the battery, and warn against typical errors, and learn what alternatives exist for safe charging without losing functionality.
Why you should turn off fast charging on Xiaomi Mi 9
Quick Charge technology does save time, but it has hidden disadvantages:
- 🔥 Battery overheating – with accelerated charging, the battery temperature can reach 40–45°C, which destroys its chemical structure.
- ⚡ Accelerated degradation – Lithium-ion batteries lose up to 30% of capacity in 2 years with constant use of fast charging (according to a study by Battery University).
- 📉 Uneven wear – fast charging up to 80% and slow to 100% creates unstable cycles, which reduces battery life.
- ⚠️ Risk of bloating - when overheating increases the pressure inside the battery, which can lead to its deformation.
On the Mi 9 with a 3300 mAh battery, these problems are particularly acute due to its compact body and high energy density.
- 🛡️ Extend battery life by 1.5–2 years.
- ❄️ Reduce the temperature of the phone while charging by 10-15°C.
- 🔄 Stabilize the charging/discharge cycles.
⚠️ Warning: If your Mi 9 is already suffering from a bloated battery (the body is deformed, the screen is raised), turning off fast charging won’t solve the problem – a battery replacement is required!
Method 1: Disconnect via standard MIUI settings
The easiest and safest method is to use the built-in MIUI options, which is suitable for global, European and Chinese firmware (versions 12-14).
- Open the Settings app (cog icon).
- Go to the Battery and Performance section.
- Select Battery Settings → Charging.
- Find the Quick Charge option (or Quick Charge) and turn off the slider.
- Confirm the action if a warning appears.
After that, the phone will be charged in standard mode (5V/2A) and the full charge time will increase with 1 hourly 2–2,5 hours.
☑️ Preparing for Quick Charge Disconnection
If the option is not available in the menu, it means:
- 📱 You have custom firmware (like LineageOS or Pixel Experience) – read the section on alternative methods.
- 🔄 The firmware is outdated - update MIUI Up to the latest version through Settings → The phone. → Updating the system.
- 🔧 The option is hidden by the manufacturer - use the engineering menu.
⚠️ Note: On some versions MIUI For the Mi 9 (e.g. 12.5 Enhanced), the fast charging option can automatically be activated after rebooting. To avoid this, do not plug charging for 5 minutes after disconnecting - let the system save the settings.
Method 2: Use of an engineering menu (for power users)
If the standard method does not work, you can use the Engineering Mode, which requires caution, as incorrect actions can lead to malfunctions in the phone.
Instructions:
- Open the Phone app and type in the combination: ##4636## (if it doesn't work, try ##36446337###).
- In the menu that opens, select Battery Information.
- Find the Fast Charge or Quick Charge Config string and click on it.
- In the drop-down list, select Disable or Standard Charge (5V).
- Save the changes and restart the phone.
If the engineering menu does not open:
- 🛠️ Install the app MTK Engineering Mode (Qualcomm Snapdragon 855 processors in Mi 9 will suit Qualcomm Engineer Mode).
- 🔐 On some firmware, access to the engineering menu is blocked - you will need to unlock the bootloader.
What if the engineering menu does not save the settings?
| Method of disconnection | Difficulty | Root is required. | Post-reset reset |
|---|---|---|---|
| Standard settings of MIUI | ⭐ (simple) | ❌ No. | Sometimes. |
| Engineering menu | ⭐⭐ (middle-of-the-road) | ❌ No. | Often |
| ADB-team | ⭐⭐⭐ (difficult) | ❌ No. | No. |
| Applications (AccA, Battery Charge Limit) | ⭐⭐ (middle-of-the-road) | ✅ Yes. | No. |
Method 3: Disable Quick Charge via ADB (without root)
If previous methods have not helped, you can use them. ADB-This is a way that doesn't require root rights, but it requires a computer and enabled debugging. USB.
Step-by-step:
- Turn on Developer Mode: Go to Settings → About Phone. Click 7 times on MIUI until you become a developer!
USB debugging
Settings → Additional → For Developers
ADB-driver
cmd
adb devices(The Xiaomi Mi 9 device should be available).
adb shell settings put global battery_charge_limit 0adb shell settings put global fast_charge_enabled 0Reboot the phone.
To return fast charging, use:
adb shell settings put global fast_charge_enabled 11. Reinstall Xiaomi USB Drivers drivers.
2. Use the original USB Type-C cable from the kit.
3. Enable the option Cancel authorization in the developer settings USB and reconnect.-->
Method 4: Applications for charging control (root required)
If you have root rights, you can use specialized utilities to adjust charging flexibly.The best options for the Mi 9 are:
- 📱 AccA (Accumulate Charge Alarm) – allows you to limit the charging current, turn off Quick Charge and set the charge limit (for example, up to 80%). XDA.
Instructions for AccA:
- Install the application and provide root access.
- Go to the Charge Control section.
- Activate the Disable Fast Charge option.
- If necessary, set a charge limit (80 percent is recommended for maximum battery life).
⚠️ Note: Using root applications can lead to loss of warranty (if it is still valid) and unstable operation of the phone. → Additionally. → Backup and reset.
What to do if nothing helps: alternative solutions
If none of these methods worked, consider these options:
- 🔌 Use a non-original adapter – fast charging only works with power supplies that support Quick Charge 4+. Connect your phone to the charging with the exit 5V/2A (For example, from an old smartphone).
If you decide to replace the battery, choose the original battery with the article MBJ404815 (capacity 3300 mAh).
- Baseus (BS-BATXM9) is a reliable option with a 1-year warranty.
- Remax (RMB-3300 series) is a budget alternative.
💡
For maximum battery life, combine this method with other measures: avoid full discharge, avoid using the phone in extreme temperatures (below 0°C or above 35°C), and calibrate the battery once every 3 months (full charge/discharge cycle).