How to check the battery on Xiaomi Mi 9T: from the code *#*#4636#*#*** to disassembly

Xiaomi Mi 9T (also known as Redmi K20 in some regions) is one of the most popular smartphones of the brand, but even its battery of 4000 mAh is not eternal. After 2-3 years of active use, the battery capacity can fall by 30-40%, leading to rapid discharge, sudden blackouts and overheating. In this article, we will discuss 7 working methods of checking the status of the battery – from hidden engineering menus to disassembly of the device and visual diagnostics.

It's important to understand that the Mi 9T has a non-removable battery, so some of the techniques require caution, and we're not going to advise you to take your phone apart without experience, but instead, we're going to show you how to evaluate the wear and tear without risking damage to the device, and if you do decide to do a physical exam, we'll give you a safety checklist.

This article is relevant for all Mi 9T modifications (including Mi 9T Pro) as they use similar MIUI-based power controllers and firmware.

1. Check through the engineering menu (#4636##)

The fastest way to get data about the battery is to use the hidden Android menu, which is available on all Xiaomi smartphones, including the Mi 9T, but requires care: do not change the settings unless you are sure of their purpose.

Instructions:

• 📱 Open the phone app and enter the combination: ##4636##.
• 🔋 In the menu that appears, select Battery Information).
• 📊 Pay attention to the parameters: Level (Level) – current percentage; Status – should be Charging or Discharging; Temperature – norm 25–40°Voltage: 3.7-4.2 V; Technology: Li-ion or Li-poly.

⚠️ Note: If the menu displays Unknown instead of battery data, it may mean a controller failure or an unoriginal firmware.

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If the engineering menu doesn't open, try entering the code through the Google Phone app (available on the Play Market).The standard MIUI Dialer app sometimes blocks service combinations.

2. Use of diagnostic applications

Specialized utilities allow you to get more detailed information about the battery, including the actual capacity, the number of charging cycles and the degree of wear. 9T The following programs will be appropriate:

We recommend starting with AccuBattery, which is the simplest and most informative.

1. Charge your phone to 100% and connect to the app.
2. Wait until the statistics are collected (usually 1-2 charging cycles).
3. Check the Health tab – there will be a percentage of wear.

Critical indicator for Mi 9T: if the wear exceeds 40%, it is time to replace the battery - the risk of sudden shutdown at 20-30% of charge increases by 3 times.

3.Analysis through ADB (for advanced users)

If you want the most accurate data directly from the system, you can use Android Debug Bridge (ADB), a method that requires connecting the phone to a PC, but gives you access to hidden settings that do not show the applications.

Instructions:

1. Install Platform Tools on your computer.
2. Enable USB Debugging on Mi 9T: Go to Settings → About Phone → MIUI Version (click 7 times to unlock Developer Mode), then to Settings → Additional → Developer → Debugging on USB.
3. Connect your phone to your PC and type in the command line: adb shell dumpsys battery

In the answer, note:

• 🔋 level - current charge;
• 🌡️ Temperature: Temperature in tenths of a degree (e.g, 320 = 32.0°C);
• ⚡ Voltage - Microvoltage (divided by 1000 to get volts);
• 🔄 charge counter - real capacity in microamper-hours (divided by 1000 for mAh).

⚠️ Note: If the charge counter is much lower than the passport 4000 mAh (for example, 2500-3000), this confirms critical wear. Also check health - if there is not 2 (good condition), the battery requires replacement.

Visual inspection of the battery (during disassembly)

If you're ready to disassemble the Mi 9T, you can physically test the battery, which is the last resort, but it gives you 100% certainty of diagnosis, and caution: disassembly will void the warranty (if it's still valid) and risk damaging the plumes.

Checklist before disassembly:

Signs of a faulty battery:

• 🔥 Bloating – if the battery case is deformed, it must be replaced urgently (the risk of fire!);
• 💧 Electrolyte dashings – white or green traces on the board;
• 🔌 Contact oxidation - green coating on connectors;
• 📉 Loss of capacity – if the label says 4,000 mAh and the actual size is less.

⚠️ Warning: If the battery is swelling, don't try to puncture or heat it, it could lead to a fire.

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Even if the visually normal battery looks, the capacity may have been reduced by internal degradation, so visual inspection is better combined with software diagnostics.

Discharge test (method "100 to 0 per cent")

It doesn't require disassembly or special programs, but it takes time, and the idea is to measure how much the phone will last on a single charge at a standard load. 9T With a new battery, normal performance:

• 📵 Standby mode: 2-3 days;
• 📱 Average load (social networks, messengers): 6-8 hours;
• 🎮 Games/video: 3-5 hours.

How to run the test:

1. Charge your phone to 100% and disconnect from the network.
2. Use it in normal mode, fixing the time.
3. When the charge reaches 1%, check how many hours have passed.

If the battery life has decreased by 30-50% from the initial values, this indirectly confirms the wear of the battery. For example, if the Mi 9T used to hold a charge for 7 hours, and now it is 3-4, it is time to think about replacing it.

6. Verification through Xiaomi service codes

Xiaomi hides a few useful codes for iron diagnostics, and they work on the Mi 9T regardless of the MIUI version:

• 🔢 ##6484## - battery test (shows voltage, temperature, state);
• 🔢 ##64663## - General hardware diagnostics (includes battery checks);
• 🔢 ##284## - Vibration and charging test (useful if the phone is not charging).

After you enter the code ##6484##, you will see a menu with the Battery tab.

• Battery Voltage - Voltage - Voltage
• Battery Temperature: Temperature;
• Battery Health (Good/Unknown)

If you see Unknown or Replace instead of Good, it’s a direct signal to replace the battery.

7. Diagnosis through MIUI Battery Care

MIUI 12 and later has a built-in Battery Care feature that analyzes battery status to find it:

1. Go to Settings → Battery and Performance.
2. Put it on the icon. ⚙️ (gear) in the upper right corner.
3. Choose Battery Care (Battery Care).

This is the following:

• 📊 Battery Health (Battery Health);
• 🔄 Number of charging cycles;
• 🛡️ Recommendations for extension of service.

⚠️ Note: If this menu indicates that the battery requires maintenance, this cannot be ignored – further operation may damage the power controller.

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Battery Care only appeared in MIUI 12+. If you have an older version, update your firmware or use other methods from this article.

FAQ: Frequent questions about the Xiaomi Mi battery 9T