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

Xiaomi Redmi 9 is one of the most popular budget smartphones, but many users face a problem: the device charges too slowly, even if you use a proprietary adapter. The reason often lies in the default fast charging function. In this article, we will discuss how to activate it, what nuances to consider when choosing a charger and why sometimes even after turning on the speed remains low.

It’s important to understand that Redmi 9 supports Quick Charge 3.0 (18W), but the manufacturer doesn’t always include it out of the box. This is designed to extend battery life, but you can manually activate it if necessary. We’ll look at official and alternative methods, and we’ll also deal with the myths about the “harms” of fast charging for the battery.

If you've tried to turn on the feature through the settings, but nothing has changed, don't be quick to blame the smartphone. It could be a cable, a power supply, or even a firmware problem. Below you'll find a checklist for diagnosis and problem solving.

1. Checking the compatibility of the charger

Before you enable fast charging on the Redmi 9, make sure your adapter and cable support Quick Charge 3.0 or Power Delivery (PD) technology. Xiaomi's original kit for this model usually comes with a 10W (5V/2A) unit that doesn't provide top speed.

Here are the key parameters that should be considered:

• 🔌 Adapter power: minimum 18 Watt (9V/2A or 12V/1.5A). Optimally — 20–30 Watt.
• 🔗 Cable: must support current 2A Cheap cables often limit power.
• 🏷️ Certification: Look for labeling QC 3.0, PD or USB-IF adapter.
• 📱 Compatibility with Xiaomi: some brands (such as Anker or Baseus) release adapters optimized for Xiaomi devices.

If you’re using a charger from another device (like the Redmi Note 10 or POCO X3), check its specs. For example, an adapter from the POCO F3 (33W) will work with the Redmi 9, but the speed will be limited to 18W due to hardware limitations of the smartphone.

⚠️ Warning: Do not use adapters with power above 30W without official Xiaomi certification.This can cause the power controller to overheat and shorten battery life.

2. Enabling fast charging through settings

The easiest way to activate the function is through the standard MIUI menu, but in some firmware versions, this item may be hidden.

1. Open Settings → Battery and Performance.
2. Select Charging (or Battery Settings in older versions of MIUI).
3. Find the Quick Charge option (could be called Quick Charge or Accelerated Charge).
4. Activate the switch. If there's no point, move to the next section.

If there is no option, this may mean:

• 📱 You have a stripped-down firmware (for example, for the European market).
• 🔄 The function automatically shuts down when the battery wears too much (more than 80% of cycles).
• 🔧 The smartphone activated the mode of energy saving, which blocks fast charging.

Turn off the power saving mode

Check the wear of the battery in Settings → Battery → Status

Update MIUI to the latest version

Use an original or certified cable-->

Once activated, check the charging speed with apps like AccuBattery or Ampere. Normal rates for Redmi 9:

• 🔋 0–50%: 15–18 W (about 2% per minute).
• 🔋 50–80%: 10–12 W (slowing down to protect the battery).
• 🔋 80–100%: 5–7 W (drip charging).

💡

If after turning on fast charging smartphone warms up stronger than usual, remove the case and charge in a ventilated place. the temperature above 40 ° C automatically reduces the charging power.

Alternative method: engineering menu

If you don’t have a quick charge option in your settings, you can try activating it via the engineering menu (#4636###), which doesn’t work on all versions of MIUI, but it often helps unlock hidden features.

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 the Fast Charge (which may be called Quick Charge Config).
4. Activate it by selecting Enabled.
5. Reboot your smartphone.

Important: On some firmware, after activation through the engineering menu, the function may reset after the system update, in which case the procedure will have to be repeated.

If the engineering menu is not available or does not contain the desired item, try another method:

1. Install the MTK Engineering Mode app (only for MediaTek-based smartphones, which include Redmi 9).
2. Go to the Hardware Testing → Battery section.
3. Find the Fast Charging option and turn it on.

⚠️ Attention: Changes to the engineering menu can cause the smartphone to work unstable. Do not change other settings unless you are sure of their purpose. → System system → Resetting settings.

4.Problems and Solutions: Why Fast Charging Doesn't Work

Even after the feature is turned on, users often find that the smartphone is charging at the same speed.

🔌 Problem: Charging is 5-10 W instead of 18 W

• 🔍 Reason 1: The cable doesn't support high current. Try replacing it with a certified one. USB-C marked 3A.
• 🔋 Reason 2: The adapter is not compatible with Quick Charge 3.0. Check its specifications (see table in section 1).
• 📱 Reason 3: Power saving mode is on. Turn it off in Settings. → Battery.
• 🔄 Reason 4: The smartphone is overheating. Let it cool or take off the case.

⚡ Problem: Fast charging only works up to 50-60%, then slows down

This is normal behavior for the Redmi 9.The manufacturer specifically limits power in the last phase to reduce battery load.If you need to speed up the process, disconnect the smartphone from charging when it reaches 80% and wait for cooling, then plug it back in again.

🚫 Problem: Fast charging option is not available in settings

In this case:

• Update MIUI to the latest version via Settings → About Phone → System Update.
• Check the firmware region. For example, in the global version (MIUI Global), the function can be disabled, and in the Chinese version (MIUI China) it is available.
• Install custom recovery (like TWRP) and run a modified QC 3.0 kernel module (power users only!).

💡

If the fast charging has not worked after all the manipulations, the problem may lie in the wear of the power controller or battery, in which case contact the service center.

5. Myths about fast charging: what's true and what's not

There's a lot of rumors going around Quick Charge technology, and we'll deal with the most common ones.

🔋 Myth 1: Fast charging will ruin your battery in a few months

Modern smartphones (including the Redmi 9) use multi-stage charging algorithms that minimize wear and tear.

• Up to 80% of the charge goes at maximum power.
• After 80%, the speed decreases and the voltage stabilizes.
• At 100%, the power is turned off and the battery is recharged with short pulses.

Studies show that when used correctly, the wear difference between normal and fast charging is only 5–10% after 500 cycles.

⚡ Myth 2: Any high-power charger can be used.

For example, a 65-watt adapter from a laptop might give too much voltage to a Redmi 9 controller, which would result in:

• Overheating the fee.
• Battery malfunction.
• Automatically shut down charging (protection doesn’t always work!)

Use only certified adapters with QC 3.0 or PD support.

📱 Myth 3: Fast charging only works with the original cable

That's not true. The key is to have a 2A or higher cable and a better squish, like Anker, UGREEN or Baseus cables, which often work better than the original cables.

To check the actual charging speed, use the Ampere app (showing real-time current) or AccuBattery app (analyzing battery health).

6.Optimizing charging: how to extend the life of the battery

Even if you’ve turned on fast charging, it’s worth the flollow to make the Redmi 9 battery last longer:

• 🔋 Avoid full discharge. Optimal range is 20-80%. Regular discharges to 0% reduce battery life.
• 🌡️ Control the temperature. Don't charge your smartphone at temperatures above 35.°C or below 0°C.
• 🔌 Turn off charging after 100%. Long-term connection to the network in 100% state accelerates degradation.
• 📵 Do not use your smartphone while charging for resource-intensive tasks (games, video) and this increases heat.
• 🔄 Calibrate the battery once every 3 months: fully discharge, then charge to 100% without interruption.

MIUI has a built-in charging optimization feature:

1. Go to Settings → Battery → Battery settings.
2. Enable Adaptive Charging (or Optimized Charging) option.
3. The smartphone will automatically limit the charge to 80% and bring it up to 100% just before the intended shutdown (based on your habits).

If you notice that the battery is rapidly discharged, check its condition:

1. Open Settings → Battery → Battery status.
2. Look at the capacity. If it's below 80 percent of the original capacity, it's time to replace the battery.

💡

For accurate diagnosis, use the Throttling Test CPU app, which will show if the processor is losing performance due to battery wear.

7. Frequent User Questions (FAQ)