The Xiaomi Mi 9T (also known as the Redmi K20 in some regions) remains a popular device even years after its release, but over time, many owners face a problem: the phone stops charging or does it extremely slowly, and the reasons can be due to both banal wear and tear accessories, and serious hardware malfunctions.
In this article, we will systematically analyze all possible reasons why the Mi 9T does not charge, from the obvious (damaged cable) to the hidden (failure of the firmware or power controller). You will learn how to diagnose the problem yourself, what measures to take first, and when to contact the service center.
Important: If your Mi 9T is dead and doesn't respond to charging, don't panic. 60 percent of the time, it's done by changing the cable or cleaning the connector. But there are more insidious scenarios, and you can read about them below.
1. Checking of charger and cable
Start with the simplest: 9 out of 10 charging problems are due to a faulty cable or adapter. Xiaomi Mi 9T supports Quick Charge 3.0 (18 watts), but even the original power supply fails over time.
- 🔌 Test with another cable: take a knowingly working USB-C cable (preferably original or Xiaomi certified) connect to the same adapter. If charging started, the cable is a problem.
- ⚡ Adapter check: try charging your phone from another power supply (e.g. laptop or power bank) and if it's charging, your adapter won't give you the voltage it needs.
- 📱 Diagnostics on another device: connect your cable and adapter to another smartphone. If it's not charging, the problem is the accessories.
Notice the signs of cable malfunction: melted areas, bending, poor contact when moving. Mi 9T is especially sensitive to cable quality due to the high power of fast charging. Cheap uncertified wires can not only not charge, but also damage the power controller of the phone.
If you use wireless charging (via an adapter), note that the Mi 9T does not directly support Qi-standard. Any "wireless" solutions for this model are crutches with adapters, which often cause problems.
2. Cleaning of the Type-C connector and contact diagnostics
The USB Type-C connector in the Mi 9T is one of the most vulnerable places, and because of the frequent connection/disconnection of the cable, the ingestion of dust or moisture, the contacts become oxidized or contaminated, this leads to:
- 🔋 Slow charging (phone shows Charging, but the percentage is almost not growing).
- 🔄 Periodic disconnection/connection of charging.
- ❌ Complete lack of response to cable connection.
How to clean the connector:
- Turn off the phone and remove it. SIM-card (if it interferes with the).
- Take a wooden toothpick (not metal!) and carefully remove visible dirt from the connector.
- Soak the cotton swab in isopropyl alcohol (not vodka!) and wipe the contacts. Let it dry for 10-15 minutes.
- Blow the connector with compressed air (for example, a canister to clean the keyboard).
⚠️ Warning: Never use metal objects (needles, paper clips) to clean, which can close contacts and disable the charging controller. Also avoid wet wipes: moisture corrodes the contacts.
If the problem remains after cleaning, examine the connector for mechanical damage:
- Bending or missing contacts (especially central ones responsible for data transmission and power supply)
- A loose connector (backlash when connecting the cable).
- Traces of oxidation (green or white coating on contacts).
In such cases, you will need to replace the connector, which will cost 1,500-2,500 rubles in the service center. Self-repair is not recommended - the risk of damage to the motherboard.
Turn off the phone and remove the battery (if possible)|
Use only wooden/plastic tools |
Do not use water or aggressive liquids |
Allow the connector to dry completely before switching on |
Check charging after cleaning-->
3. Battery problems: wear and tear
The Xiaomi Mi 9T battery has a capacity of 4000 mAh and is designed for ~500 full charging cycles. After 2-3 years of active use, its capacity can fall to 60-70% of the original, which leads to:
- 🔋 Quick discharge (the phone sits down in a few hours without loading).
- ⚡ Slow charging (0 to 100% in 4-5 hours instead of 1.5-2 hours).
- ❌ Complete charging failure (the phone is powered only by the cable but not charged).
How to check the status of the battery:
- Go to Settings → Battery → Battery status. If the capacity is below 80%, it is time to change the battery.
- Use applications like AccuBattery (Android) for detailed diagnostics. Pay attention to the parameters: Battery Health should be above 80%; Temperature if above 40°C when charging, it is a sign of degradation; Charging time - from 0 to 100% should take no more than 2 hours when using the original RAM.
⚠️ Warning: If the phone suddenly turns off at 20-30% charge or shows a “jumping” percentage (for example, from 50% drops to 15%), this is a sure sign of a malfunction of the battery controller.
The cost of replacing the battery in the Mi 9T:
| Type of service | Cost (rupe) | Guarantee | Repair time |
|---|---|---|---|
| Official Xiaomi service | 3 500–4 500 | 6–12 months | 1-3 days |
| Informal service | 2 000–3 000 | 1-3 months | 1-2 hours |
| Self-sustaining replacement | 1,200–1,800 (battery cost) | No. | 30-60 minutes |
If you decide to change the battery yourself, consider:
- 🛠️ It'll take a special glue. B7000 fixing.
- 🔥 Risk of damaging plumes or motherboard during dismantling.
- ⚠️ The new battery must be original or from a proven manufacturer (e.g., a new battery must be manufactured by a manufacturer, ZOP, CB). Cheap analogues may swell or not hold the charge.
💡
Before you replace the battery, back up your data! During the repair process, the phone will have to completely discharge and disconnect, which can lead to a reset.
4. Software failures
Sometimes the Mi 9T doesn't charge due to software errors, especially after MIUI updates or custom firmware installation.
- 🔄 Phone shows "charge" but the percentage does not increase.
- ⚡ Charging is only in the off state.
- 📱 Notification: "Charger not supported".
How to fix software failures:
- Phone reboot: Sometimes a banal reboot helps. Press the power button for 10 seconds until the phone turns off, then turn it on again.
- Reset Charging Settings: Go to Settings → Applications → Application Management → Three Points (menu) → Resetting Application Settings. This will reset the cache of the system services responsible for power.
- Update MIUI: check for updates in Settings → About Phone → System Update. Sometimes charging bugs are fixed in new firmware versions.
- Reset to factory settings: if nothing helps, back up the data and reset to Settings → Additional → Restore and Reset → Reset settings.
For advanced users:
- 🛠️ Fastboot flashing: If the phone isn't charging or turning on, you can try hand-stitching it with the Mi Flash Tool. Instruction: 1. Download the latest firmware for Mi 9T From en.miui.com. 2. Install Xiaomi and Mi Flash Tool drivers on PC. 3. Transfer your phone to Fastboot mode (clip Power). + Volume reduction). 4. Connect to your PC and run through the Mi Flash Tool.
- 🔧 Reverse to the old version MIUI: If the problem appeared after the update, you can roll back to the previous version of the firmware.
⚠️ Attention: Unprofessional firmware can lead to a breeze (completely inoperable) of the phone.
What if the phone is dead and does not respond to charging?
5. Faulty of the power controller
If all previous methods failed, the problem may lie in the power controller, the chip on the motherboard that controls charging and power distribution. In the Mi 9T, it is a common "disease," especially after:
- 🔌 Use of non-original chargers.
- ⚡ Voltage surges (for example, charging from an unstable socket).
- 💧 Moisture intrusion into the shell.
Signs of Controller Failure:
- The phone is not charged from any cable/adapter.
- Charging is only in the off state.
- The phone warms strongly in the camera area when connected to charging.
- You smell smoke or smoke from the Type-C connector.
Diagnostics and repairs of the power controller are a challenge for professionals.
- Diagnostics with a multimeter to check the voltage on the contacts.
- Re-silver or replace the controller (cost - from 3000 to 8 000 rubles).
- Check the power supply chain for breaks or short circuits.
⚠️ Warning: If the power controller is burned, further attempts to charge the phone could damage the motherboard!
The cost of repairing the controller in the Mi 9T:
| Type of malfunction | Cost (rupe) | Duration of repairs |
|---|---|---|
| Replacement of the power controller | 3 000–5 000 | 1-2 days |
| Repair of the supply chain (seduction) | 2 500–4 000 | 2-3 days |
| Replacement of motherboard | 8 000–12 000 | 3-5 days |
💡
The power controller is one of the most expensive malfunctions. If the phone is older than 3 years, it is sometimes cheaper to buy a new smartphone than to repair the old one.
External factors: moisture, overheating, mechanical damage
Sometimes the Mi 9T stops charging due to external influences that owners do not always notice immediately.
- 💦 Moisture: Even if the phone is not sinking, condensation or high humidity can cause contacts to corrosion. Signs: The phone stopped charging after being in the bathroom or in the rain. A notification appears on the screen saying "Moisture in the charging connector." Type-C contacts are green or white-colored. What to do: Turn off your phone immediately, remove the battery (if possible), and dry in rice or silica gel for 24 to 48 hours. Don't try to charge until completely dry!
- 🔥 Overheating: If the phone is heated above 45°C, the system automatically turns off charging for safety. Reasons: Use during charging (games, video), Charging under direct sunlight, faulty battery or controller. Solution: let the phone cool to room temperature, then try charging again. If the heat is repeated, check the battery and controller.
- 💥 Mechanical damage: falls or impacts can disrupt the battery's connection to the motherboard. Signs: The phone doesn't charge after a fall, the body is deformed in the area of the connector or battery, artifacts appear on the screen (strips, flickering). In the service will check the integrity of plumes and contacts using a microscope.
Prevention of external damage:
- 🛡️ Use a case with moisture protection (for example, with certification) IP67).
- ☀️ Avoid charging at temperatures above 35°C or below 0°C.
- 🚫 Do not drop your phone or press the screen/body while charging.
7. When to contact the service center
If you’ve tried all the methods in this article, but the Mi 9T still doesn’t charge, it’s time to contact the professionals.
- 🔧 The phone does not charge from any cable/adapter, and cleaning the connector did not help.
- ⚡ Notifications of a critical charging error appear on the screen.
- 🔥 The phone is very warm or makes extraneous sounds (crackling, squeaking) when connected to charging.
- 💥 The battery is swelling (the phone body is noticeably arched).
- 📱 The phone is powered on only from charging, but does not hold the charge after switching off.
How to choose a service center:
- Official service Xiaomi: pros – warranty for repair, original spare parts; cons – high cost and queues.
Average prices for repairs in Moscow (2026):
| Service | Official service | Informal service |
|---|---|---|
| Diagnostics | 500-1000 rubles. | Free (when repaired) |
| Replacement of Type-C connector | 2,500-3,500 rubles. | 1,500-2,500 rubles. |
| Battery replacement | 3,500-4,500 rubles. | 2,000-3,000 rubles. |
| Repair of the power controller | 5,000-8,000 rubles. | 3,000-5,000 rubles. |
⚠️ Note: Before handing over the phone for repair is mandatory: Make a backup of the data (if the phone turns on). Make sure the service uses original spare parts (ask for certificates). Check the reviews of the workshop on independent sites (for example, Yandex.Maps, 2GIS). FAQ: Frequent questions about charging Xiaomi Mi 9T ❓ The phone shows Charging, but the percentage doesn't increase. What's the matter? It's a typical sign of a faulty cable, a dirty connector, or a worn-out battery. Start by changing the cable and cleaning the Type-C port. If it doesn't, check the battery capacity in Settings. → Battery. ❓ Can I charge the Mi? 9T But remember, the Power Bank needs to support Quick Charge 3.0 (18 watts) for full charging, and cheap power banks may not be giving out enough voltage, which will cause the phone to charge very slowly. Avoid charging from power bank at temperatures below 0°C or higher than 40°C. ❓ Why does the phone only charge when it's off? It's a sign of a power controller malfunction or a battery wear is bad. When it's off, the phone uses less power, and the low charging current at least keeps it going. The solution is to replace the controller or battery. ❓ After updating MIUI The phone stopped charging fast. What do you do? Updates sometimes reset your charging settings. Try: Enable fast charging in Settings. → Battery. → Fast Charging. Reset the Battery app settings to Settings → Annexes → Application management → Battery → Warehouse → Clear the cache, roll back to the previous version. MIUI (If the problem has occurred after the update). ❓ How much does it cost to replace the battery in Mi 9T 2026? The cost depends on the type of service: Official service: 3,500-4,500 rubles. (with a guarantee of 6-12 months). Informal service: 2,000-3000 rubles. (warranty of 1-3 months). Self-replacement: 1,200-1,800 rubles. (battery cost) + tools. We recommend the original Xiaomi battery or certified analogues (ZOP, CB).