How to enable fast charging on Xiaomi Mi 9: all the ways and nuances

Xiaomi Mi 9 is the flagship smartphone of 2019, which supports fast charging technology Quick Charge 4+ (up to 27 watts). However, many users are faced with the fact that the device charges slower than expected, although the original power supply and cable are present. The reason often lies in software settings or incompatible accessories. In this article, we will discuss all the ways to enable fast charging on the Mi 9, from standard settings to hidden functions of the engineering menu.

It is important to understand that fast charging on Xiaomi works only if three conditions are met: the correct power supply (at least 18 W), high-quality charging. USB-cable (preferably original) and activated option in the settings. If any of them are not met, the smartphone will charge in standard mode (5-10 watts). MIUI 12–14 and identify the most effective solutions.

1. Verification of compatibility of chargers

The first thing to do is make sure your charger supports Quick Charge 4+/4.0/3.0 or Power Delivery (PD).The Xiaomi Mi 9 comes with the original 27W power supply (MDY-11-ED model), but many users lose it or use third-party charges.

Here is a list of compatible standards and capacities:

• ⚡ The original Xiaomi block 27W — The best option, provides maximum speed.
• ⚡ Quick Charge 4+/4.0 (18W and above) – works, but the speed may be lower 10–15%.
• ⚡ Power Delivery (PD) 18W+ — Compatible but requires a cable with support PD.
• ❌ Standard charging 5W/10W — fast charging is not activated.

To check the power of your unit, look at the label: it should be Quick Charge, PD or an indication of 9V/2A, 12V/1.5A and higher. If the unit is unmarked, it probably does not support fast charging.

2. Fast charging settings in MIUI

By default, the Xiaomi Mi 9 should automatically activate fast charging when you connect a compatible unit. However, in some firmware (MIUI 12.5 and older), this option can be disabled or hidden.

1. Go to Settings. → Battery.
2. Put it on the icon. ⚙️ (Additional battery settings).
3. Find the Fast Charge (or Quick Charge in English).
4. Activate the switch if it is switched off.

If the Fast Charging option is not on the menu, it could mean:

• 🔹 Your firmware has been modified (castomy) and the function has been removed.
• 🔹 The smartphone does not recognize the power supply as compatible.
• 🔹 Charging optimization is enabled (see next section).

3. Disabling charging optimization

Charging optimization (or Adaptive Charging) limits charging speeds to 80-90% to extend battery life, which is good for the battery, but prevents fast charging.

1. Open Settings → Battery → Battery status.
2. Find the option “Optimize charging” (or Adaptive Charging).
3. Turn off the slider or select No Limits.

After that, the smartphone will be charged at full power, but remember: frequent charging up to 100% can reduce battery life by 10-15% in 1-2 years.

💡

If you rarely use fast charging, leave the optimizations on – this will extend the battery life by 200-300 cycles.

4. Checking the cable and USB port

Even with the right power supply, fast charging may not work because of the cable.The original cable from Xiaomi Mi 9 has increased thickness of the rods (24 AWG) and Quick Charge support.Third-party cables often don't meet the requirements.

How to check the cable:

• 🔌 Connect the original cable from the kit - if charging has accelerated, the problem is in the third-party accessory.
• 🔍 Check the USB Type C connector on your smartphone: dirt, oxidation, or damaged contacts can block fast charging.
• 📱 Try another port on the power supply (if it's multiport).

If the ports are contaminated, clean them carefully with a wooden toothpick (not metal!). For deep cleaning, use isopropyl alcohol (90%+) and cotton swab.

5.Reset battery settings

If all previous steps failed, the problem may lie in the battery system settings, resetting the power settings will return factory values and often solves the problem with slow charging.

How to reset your settings:

1. Go to Settings → Applications → Application Management.
2. Tap it on three points (⋮) in the upper right corner and select Reset application settings.
3. Confirm action. It won't delete data, but it will reset permissions and background activity.

After reset, restart your smartphone and check the charging speed. If the problem persists, proceed to the next method.

💡

Resetting battery settings helps in 60% of cases where fast charging doesn’t work for no apparent reason.

6. Activate fast charging via engineering menu

If standard methods don’t work, you can try enabling Quick Charge via the engineering menu (#4636###), which is suitable for power users, as incorrect settings can disrupt the smartphone.

Instructions:

1. Open the Phone app and enter the combination: ##4636##.
2. Select Battery Information (Battery Information)
3. Check the AC Charge string – if the value is less than 18W, fast charging is inactive.
4. Go back to the main menu and select Hardware Testing → Charging.
5. Activate the Fast Charge option (if available).

If there is no Fast Charge item in the engineering menu, it means that your firmware does not support manual activation, in which case only firmware through Fastboot or contacting a service center will help.

💡

Before entering the engineering menu, back up the data. Unknown parameters are best not changed!

7.Firmware problems and their solution

On some versions of MIUI (especially custom ones), fast charging can be turned off at the kernel level. If you use unofficial firmware, try:

• 📱 Back on the stock. MIUI via Mi Flash Tool.
• 🔄 Update your smartphone to the latest version MIUI through settings → Updating the system.
• 🛠️ Install a modified kernel (e.g., FrancoKernel) that supports Quick Charge.

Before you run the firmware, check the compatibility of the MIUI version with your Mi 9 model. Incorrect firmware can lead to a "brick" (complete failure) of the device.

⚠️ Note: Fastboot firmware erases all data from the device. backup via Mi Cloud or TWRP.

FAQ: Frequent questions about fast charging Xiaomi Mi 9