Why fast charging on Xiaomi Redmi Note 8 Pro disappeared: a full analysis of the causes and solutions

Why the smartphone suddenly stopped charging quickly

You're used to the Xiaomi Redmi Note 8 Pro charging from 0 to 100% in less than an hour, but suddenly noticed: the indicator shows Charging, and the percentages crawl like a snail? Or the phone even writes "Slow Charging", although you use the original 18W adapter? This problem is familiar to many owners of the model - and it has at least 7 different reasons.

Unlike software glitches (when you just reboot your smartphone), fast charging loss is often associated with physical wear and tear, firmware errors, or even factory failure. In this article, we’ll look at all possible scenarios, from trivial connector contamination to hidden MIUI settings that can block high currents, and you’ll learn how to self-diagnose a fault and return the previous charging speed without contacting the service.

Spoiler: 60 percent of the time, it's solved in 10 minutes and it doesn't take a phone to disassemble, but there are some cases where you can't do without a soldering iron or parts to be replaced. Let's get this straight.

1. Damaged cable or adapter: first check

Start with the obvious, check the charging kit. Even the original Xiaomi cable wears out over time, rubbing the veins, oxidizing the contacts, and the adapter can burn out due to voltage surges, and everything may look normal on the outside, but inside there are cliffs or short circuits.

How to check:

• 🔌 Connect the Redmi Note 8 Pro to another adapter with Quick Charge support 3.0/4.0 (For example, from the Redmi Note 9 pro POCO X3). If charging went faster - the problem is in your power supply.
• 🔄 Try another cable (preferably original or certified) USB-C). Cheap Chinese cords often do not support high currents.
• 🔍 Check the cable connector for darkening, melting, or contamination. If the contacts turn black, it's a sign of overheating.

Note: The Redmi Note 8 Pro requires an adapter with a 9V/2A or 12V/1.5A output voltage to activate fast charging. If your unit only outputs 5V/2A, the phone will charge in "slow" mode.

2.Contaminated USB-C connector: how to clean without damage

The USB-Type C connector in the Redmi Note 8 Pro is one of the most vulnerable areas, and the dust, the villi from the pocket, the residue of liquid or the oxidation of the contacts can disrupt the tight fit of the cable, causing the phone to fail to recognize the supported fast charging protocol and go to standard mode.

How to clean the connector:

1. Turn off your phone and take out the SIM cards (to avoid short circuits).
2. Illuminate the connector with a flashlight - if you see debris, carefully remove it with a plastic toothpick or compressed air (a canister for cleaning equipment).
3. To remove oxidation, use alcohol wipes (not cotton swabs!), dipped in isopropyl alcohol (90%+).
4. Allow the connector to dry for 10-15 minutes before connecting the cable.

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Never use metal objects (needles, paper clips) to clean the connector – they can damage the contacts and cause short circuit.

If the problem persists after cleaning, check the density of the cable: it must enter the connector with a slight click. If the backlash is felt, the locking tongue inside the connector may be bent (it requires disassembling the phone).

3. firmware failures and hidden MIUI settings

Sometimes fast charging disappears after updating MIUI or resetting settings. In some versions of the firmware for the Redmi Note 8 Pro (especially custom) may trigger a current restriction due to:

• 🔧 Incorrect kernel settings (for example, disabled) CONFIG_USB_PD).
• 📱 Activated mode "Battery Saving" in the settings.
• 🛠️ File errors /sys/class/power_supply/battery/input_current_max (system-level current limitation).

How to return fast charging through settings:

1. Go to Settings → Battery → Battery Modes and select “High Performance”.
2. Turn off the option Settings → Battery → Charging optimization (if enabled).
3. Reset settings → System → Reset settings → Reset battery settings.

If the problem has occurred after the MIUI update, try rolling back to the previous version via Fastboot or installing a patch for the kernel (for example, the Quick Charge Enabler module in Magisk).

Battery wear or bloating: when replacement is needed

The Redmi Note 8 Pro comes with a 4500 mAh battery (BM47 or DM43) and over time, the lithium polymer cells degrade, with reduced capacity, increased internal resistance, and the battery controller artificially restricting the charging current to avoid overheating.

Signs of battery wear:

• 📉 The phone discharges in 3-4 hours with moderate use (at a rate of 10-12 hours).
• 🔥 The body warms up in the battery area even without loading.
• 🛑 Charging stops at 80-90% or goes jerky.
• 💥 Visual battery bloating (raised screen or gaps in the case).

How to check the status of the battery:

1. Type ##4636##, select Battery Information and check the health setting, if it shows Bad or Unknown, the battery is faulty.
2. Use the CPU-Z app (Battery tab) to check your current capacity, and if it's below 3,500 mAh, you should think about replacing it.

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A bloated battery is not only a loss of fast charging, but also a risk of fire. If the phone's case is deformed, immediately disconnect it from power and do not use it until the battery is replaced!

The cost of replacing the battery on the Redmi Note 8 Pro in service centers is from 1500 to 3000 rubles (depending on the battery model). Self-replacement is possible, but requires care: if the battery controller is damaged, the phone may stop turning on.

5. Problems with the power controller or motherboard

If all previous steps failed, the cause could be a faulty charging controller (SY6974 chip or BQ25890 on the motherboard) or damage to the power chains.

• 🌡️ Overheating of the phone (for example, after playing or charging in the sun).
• ⚡ Voltage jumps (use of uncertified chargers).
• 💧 Liquids (even if the phone didn’t sink, moisture could penetrate the connector).

Symptoms of hardware malfunction:

Diagnostics will require disassembling the phone and checking the voltage at key points of the board using a multimeter, for example, on the BAT+ and BAT- contacts must be 3.7-4.2V, and at the output of the controller - 9V when connecting the charge.

Turn off the phone and remove the battery

Prepare an antistatic mat and soldering station

Photograph the board before repair (for reverse assembly)

Check for spare chips (SY6974, BQ25890)

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Critical information: if the phone is switched off or restarted immediately when charging, it is a sign of a short circuit on the board, and continued use in this state can lead to irreversible damage to the motherboard.

6.The Impact of Third-Party Applications and Root Rights

Some applications (especially those that require root access) may interfere with the power controller, such as:

• 🔋 Battery calibration applications (e.g. Battery Calibration) often reset data. battery_stats.bin, resulting in failure.
• 🛡️ Magisk modules like Greenify or Battery Saver can block high currents.
• 📊 CPU overclocking programs (such as Kernel Adiutor) sometimes limit power to reduce heat.

How to get back a quick charge:

1. Remove all applications related to battery optimization.
2. If you have root, check the active modules in Magisk Manager and disable the suspicious ones.
3. Reset the settings. battery_stats.bin through TWRP (Advanced menu → File Manager Find the file in /data/system and remove it).

If you’ve recently installed custom firmware (like Pixel Experience or LineageOS), check if it supports Quick Charge for your model. Some builds turn off fast charging by default — the solution is found in the kernel settings.

7.When to contact the service: signs of serious malfunctions

If you have tried all the methods, but fast charging has not returned, most likely, the problem requires professional intervention.

• 🔧 The phone does not charge at all (even when it is off).
• 🔥 The body heats up strongly in the processor or battery area.
• 💥 On the board, blackened components or traces of burns are visible.
• 📵 Diagnosis shows an error USB port overcurrent or Charging paused.

Average cost of repairs in service centers:

Before the service visit:

1. Make a backup copy of the data (if the phone is still turned on).
2. Write down the IMEI (on the box or in About Phone settings).
3. Check whether the service uses original parts (especially for batteries and controllers).

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Do not settle for “cheap” repairs using used components – this can lead to repeated failure or fire due to incompatibility of parts.

FAQ: Frequent questions about fast charging Redmi Note 8 Pro