How to enable fast charging on Xiaomi Redmi Note 9: all ways + problem solving

Why the Redmi Note 9 doesn’t charge fast: understand the reasons

Xiaomi Redmi Note 9 supports fast charging technology Quick Charge 3.0 (18 watts), but many users are faced with the fact that the smartphone charges in standard mode - 5-10 watts. The problem lies not in the "crooked hands", but in the features of the MIUI firmware and hardware limitations. Even with the original charger, the speed can be artificially reduced due to overheating, incompatible cable or disabled option in the settings.

In this article, we will analyze all the ways to activate fast charging on the Redmi Note 9 (including the Pro, Pro Max and NFC modifications), test the real speed with different power supplies and tell you how to circumvent the limitations of MIUI. You will also learn why even after turning on the function, the smartphone can “brake” charging up to 50-70% and how to fix it.

Spoiler: 80 percent of the time, the problem is solved by replacing the cable or enabling a hidden option through the engineering menu, but there are more complicated scenarios, such as when MIUI blocks Quick Charge because of an "unoriginal" charger, although it is fully protocol compatible.

Technical Charging Features of Redmi Note 9: What Xiaomi Promises

The official specifications of Xiaomi Redmi Note 9 (model M2003J15SC for the global market) read:

• 🔋 Battery capacity: 5020 mAh (typical)
• ⚡ Support for fast charging: Quick Charge 3.0 (18W)
• 🔌 Complementary ZOO: 10 Watt (5V/2A) — Does not support Quick Charge!
• ⏱ Full charge time: ~2 hours 15 minutes (with original 18W RAM)

An important nuance: Xiaomi often saves on trim, and in the box with the Redmi Note 9 is a 10 watt charger, which is physically unable to provide fast charging. This is a marketing ploy - there is support for Quick Charge, but you need to buy a separate RAM to activate it.

If you bought a Redmi Note 9 and you expect lightning fast charging out of the box, you're going to be disappointed. Fast charging only comes on when you plug in an 18W+ compatible RAM, and even with the right power supply, MIUI can limit current -- more on that.

Method 1: Enabling fast charging via MIUI settings

In MIUI 12-14 firmware, the fast charging option can be hidden or disabled by default to activate it:

1. Open Settings → Battery and Performance.
2. Slip on Battery Settings (or additionally in older versions).
3. Find the Quick Charge option (could be called Accelerated Charge or Quick Charge).
4. Activate the switch.

If you don't have one, your version of MIUI doesn't display it.

Important: Some firmware (especially the Redmi Note 9 Pro) only offers a fast charge option when you connect a compatible charger. If you use 10W RAM, the menu item may not be available.

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To check if fast charging is activated, plug your smartphone into RAM and look at the lock screen, and if you see "Fast Charging" or a lightning icon, it works.

Method 2: Activate through the Engineering Menu (for advanced)

If standard settings don't work, you can turn on fast charging via the engineering menu, which works on most versions of MIUI, but you need to be careful:

1. Open the phone app and enter the combination: ##4636##
2. In the menu that opens, select Battery Information.
3. Scroll down and find the Fast Charge (or Quick Charge) item.
4. Slip on it and select Enable.
5. Reboot the phone.

If there's no Fast Charge, your firmware doesn't support it.

1. In the engineering menu, select Hardware Testing.
2. Go to Battery.
3. Find the Charging Control option and activate Fast Charging.

Warning: Changes in the engineering menu can lead to unstable operation of the smartphone. If after activation Redmi Note 9 began to overheat or quickly discharge - return settings to the original state.

Method 3: Checking the compatibility of the charger and cable

90 percent of the fast charging problems on the Redmi Note 9 are due to incompatible cable or power supply. Even if you're using 18W RAM, an old or damaged cable can limit current to 5W. Here's how to check the hardware:

• 🔌 Charger: Must support Quick Charge 3.0 or Power Delivery (PD). The original ZU from Xiaomi (models) will do MDY-11-ED, MDY-12-EU), and also blocks from Samsung (EP-TA800), OnePlus (Dash Charge) or Anker.
• 🔗 Cable: Must be USB Type-C → Type-C with support 5A (Cables from the Redmi Note 9 kit are often limited 2A — They need to be replaced.
• 📱 Smartphone port: Check for debris or oxidation. Clean the port with a wooden toothpick (carefully!).

How to test the actual charging power:

1. Install the AccuBattery (Google Play) app.
2. Connect the RAM and start charging.
3. Open AccuBattery → Charging and see the current power (in mA).
4. If the value is below 1500-1800 mA, charging is in standard mode.

Attention: ⚠️ Some cheap cables “deceive” the smartphone, posing as compatible with Quick Charge, but in fact limit the current. If after replacing the cable, the speed has not increased, check it with a tester or replace it with a certified one (for example, Anker PowerLine).

Method 4: Bypassing MIUI restrictions through ADB (for experienced ones)

MIUI firmware sometimes artificially restricts charging even if the hardware supports Quick Charge.This is done to "extend battery life," but you can disable the restriction via ADB (Android Debug Bridge).

Instructions:

1. Turn on Developer Mode: Go to Settings → About Phone and tap 7 times to the MIUI version.
2. Return to Settings → Additional → For developers and activate Debugging over USB.
3. Connect your phone to your PC, install it. ADB-Drivers and open the command line in the folder with the platform-tools.
4. Enter the command: adb shell settings put global fast_charge_force_enable 1
5. Reboot your smartphone.

After that, MIUI will stop limiting current and charge at maximum speed, but be careful: constant use of Quick Charge can reduce battery life by 10-15% in 2-3 years.

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ADB-team fast_charge_force_enable Forcedly includes fast charging, ignoring restrictions MIUI. However, this can cause the battery to overheat – only use if necessary.

Attention: ⚠️ Some of the updates after the update MIUI setting ADB If the charging speed has dropped again, repeat the procedure.

Why fast charging is turned off by 50-80% and how to fix it

Many users of Redmi Note 9 notice that after 50-70 percent charging speed drops sharply from 18 watts to 5-10 watts. MIUI, which:

• 🔥 Prevents battery overheating (critical temperature for Li-Pol – 45)°C).
• 📉 Extends battery life (fast charging at a high level of RAM reduces cycles).
• ⚡ Optimizes energy consumption (on the last 20% the current is always reduced).

How to get around this limitation:

1. Charge in the plane: Turn on Flight Mode - this will reduce the load on the processor and reduce heating.

If you are critically interested in charging speed at all stages, try alternative firmware. For example, Xiaomi.eu or Pixel Experience do not have strict restrictions on charging, but require unlocking the bootloader.

FAQ: Frequent questions about fast charging Redmi Note 9