How to find out the residual battery capacity on Xiaomi Mi 9T: from engineering code to hardware diagnostics

Xiaomi Mi 9T (aka Redmi K20 in some regions) is a smartphone that, even after years, remains popular due to its balanced performance and reliable hardware. But over time, any battery degrades: real capacity decreases, the life of a single charge decreases, and sometimes the device suddenly turns off at 20 to 30 percent charge. If you notice these symptoms, it’s time to check the residual capacity of the battery, a key indicator of its health.

In this article, you will find 5 proven ways to measure battery wear on the Mi 9T, from hidden engineering menus to professional diagnostic tools. We will look at which indicators are considered normal and which signal the need to replace the battery. Importantly, the methods vary in accuracy and complexity, so choose the right one based on your technical skills.

Spoiler: If your Mi 9T has been in service for more than 2-3 years, the probability of battery wear above 80% is 50-70%. But don't rush to the service - first let's figure out how to get accurate data yourself.

The fastest way to assess battery health is to use Android’s hidden engineering menu, which is available without root rights or additional apps, but doesn’t show all the options.

How to open it:

Open the Phone app.
Enter the combination: ##4636###.
In the menu that appears, select Battery Information.

In this section, you are interested in two key parameters:

🔋 Level of charge (level) – current percentage in digital form (e.g., 87).
📊 Health - this can be Good (good), Unknown (unknown) or Dead (failed). MIUI This parameter is displayed as Unknown.

The limitation of the method: the engineering menu doesn't show the actual capacity per mAh or the percentage of wear and tear. It requires a deeper analysis.

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If the menu doesn’t open after you enter the code, try using an alternative combination: ##2846579## → ProjectMenu → Background setting → Battery Log.

2.Use of ADB (for advanced users)

The Android Debug Bridge (ADB) tool provides detailed information about the battery, including actual capacity and maximum design capacity, the most accurate software method without disassembling the device.

What you need:

💻 Computer with Windows/macOS/Linux.
🔌 USB-cable (preferably original).
📱 Included debugging by USB on a smartphone (Settings) → The phone. → Version. MIUI → 7 times press to unlock the developer mode, then Settings → Additionally. → For developers → Debugging by USB).

Step-by-step:

Download ADB Tools and unpack the archive.
Connect the Mi 9T to your PC and confirm the debugging permission on your phone.
Open the command line (terminal) in the folder with ADB and type:

adb shell


dumpsys battery

In the conclusion, find the lines: capacity: X - current capacity in mkA·h (divided by 1000 for mAh). charge_counter: Y is the actual charge in μAh. health: 2 — condition (2 = good, 3 = mean, 7 = critical).

Example of output for Mi 9T with worn-out battery:

capacity: 3500000 (3500 mAh)


charge_counter: 2800000 (2800 mAh)




health: 3

Here you can see that the real capacity fell to ~80% of the original capacity of the Mi 9T – 4000 mAh.

Enable debugging on USB|Install Xiaomi drivers on PC|Use the original cable|Charge your phone to at least 50%-->

Applications for diagnostics (AccuBattery, CPU-Z)

If ADB seems complicated, specialized applications will come to the rescue, which don't give the same accuracy as hardware tests, but allow you to assess wear without connecting to a PC.

Top.-3 applications for Xiaomi Mi 9T:

Annex	Pluses	Cons	precision
AccuBattery	Shows wear in %, discharge graphs, temperature	Requires calibration (multiple charge cycles)	80–85%
CPU-Z	Displays voltage, temperature, charge level	Does not show residual capacity in mAh	60–70%
Battery Guru	Monitors charge cycles, predicts operating time	Advertising, paid functions	75–80%

How to use AccuBattery (the most informative option):

Install the app from Google Play.
Charge your phone to 100% and leave it for 1 hour to stabilize.
Use your smartphone in normal mode to a discharge of up to 20%.
In the Health section, an assessment of wear will appear (for example, 88% of the original capacity).

Step-by-step instructions for multimeter:

Remove the battery from the Mi 9T (requires plastic spatula and accuracy!).
Connect the multimeter in capacity measurement mode (Farad or mAh) to the battery terminals.
Connect the load in parallel and wait for the full discharge.
Compare the resulting value with the original capacity (4000 mAh for Mi 9T).

Example: If the multimeter showed 2800 mAh, the wear is:

(4000 - 2800) / 4000 × 100% = 30%

What to do if the capacity is below 60%?

A battery with a residual capacity of less than 60% of the nominal (<2400 mAh for the Mi 9T) is considered to be severely worn. Symptoms: - Fast discharge (1-2 hours when used actively). - Spontaneous shutdowns at 20-30% charge. - Bloating of the battery (visible on a raised screen or body). In this case, a battery replacement is recommended. The original battery for the Mi 9T has an MB-J20 article (or DM-BH50 for versions with NFC).

⚠️ Warning: Disassembling the phone voids the warranty (if it's still valid) and requires caution. Xiaomi batteries don't have short-circuit protection if mishandled!

5. Verification through Xiaomi Service Center (official method)

If you don’t want to take risks or doubt your skills, contact a Xiaomi authorized service center that uses professional equipment such as the Battery Tester BT-3562 or the Fluke BT520, which measures:

📏 Real capacity with error ±1%.
🔥 Internal resistance (norm for Li-Pol: 50-150 mOhm).
🌡️ Temperature characteristics.

The cost of diagnostics in official Xiaomi services is usually 300-500 rubles. If you need a replacement, the original battery will cost 1500-2500 rubles (depending on the region).

How to find the nearest service:

Go to the Xiaomi Service website.
Enter your city or enable geolocation.
Select the center marked Authorized (official).

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Official diagnostics are the only way to get a battery replacement warranty, and self-repairing deprives you of the right to free service if the phone is still warranty.

What to do if the battery capacity is critically low?

If the test shows wear and tear of more than 40% (capacity below 2,400 mAh), it is time to consider replacing.

1. Official replacement in Xiaomi service

✅ Pros: 6-12 month warranty, original battery.
❌ Cons: high price (from 2000 rubles), long wait (3-7 days).

2. Replacement in the unofficial service

✅ Pros: cheaper (1000-1500 rubles), faster (1-2 hours).
❌ Cons: the risk of a non-original battery, no guarantee.

3. Self-substitution

✅ Pros: Minimum cost (battery) ~800 rubles).
❌ Cons: difficult for beginners, the risk of damaging plumes.

For Xiaomi Mi 9T suitable batteries with articles:

The MB-J20 is the standard version.
DM-BH50 is for NFC models.

⚠️ Note: After replacing the battery, be sure to calibrate the power controller:

Charge your phone to 100% and hold it for 1 hour.
Turn off the charging and use until full discharge (0%).
Repeat the cycle 2-3 times.

This will help the system to correctly determine the level of charge.

FAQ: Frequent questions about the Xiaomi Mi battery 9T

🔋 What is the original battery in the Mi 9T?

In Xiaomi Mi 9T (Redmi K20) installed lithium-polymer battery capacity of 4000 mAh with a voltage of 3.85 V. Manufacturer — ATL (Amperex Technology Limited or SDI (Samsung SDI). Articula: MB-J20 — base-model. DM-BH50 — supportive NFC. Original batteries have a holographic sticker with QR-Xiaomi code and logo.

⚡ Why does your phone turn off at 20 to 30% charge?

This is a typical symptom of a battery wear or controller calibration failure. Causes: Real battery capacity has dropped below 60 percent of nominal capacity. The power controller misidentifies the charge level. One of the battery jars has failed (bloating, short circuit). Solution: check the capacity with one of the methods described. If wear is >40%, replace the battery. If the battery is normal, calibrate (see section above).

📉 Can the battery capacity be restored?

No, it's impossible to restore the original capacity of a lithium polymer battery. All "recovery" applications and methods (e.g., deep discharges) are myths. However, you can slow down further degradation: Avoid overheating (do not use your phone when charging in games); Do not discharge below 20% and charge above 80% (the optimal range for durability); Use original chargers. If the capacity has fallen below 70%, the only way out is to replace.

🔧 How to replace the battery in Mi 9T?

Replacement will require: New battery (article) MB-J20 or DM-BH50). Plastic spatula and suction cup to remove the back cover. Cross screwdriver (size) T3–T4). Double-sided tape or battery-locking glue. Step-by-step instructions: Turn off the phone and remove it. SIM-Heat the back cover with a hair dryer (60-70)°C) to soften the glue. Carefully lid the shoulder blade, starting at the bottom edge. Unscrew the 10 screws holding the metal plate. Unplug the battery plume (use plastic tweezers!). Remove the old battery and install a new one with the plume. Collect the phone in reverse order. ⚠️ Do not use metal tools to remove the battery - risk of puncture and fire!

💰 How much does it cost to replace the battery in Mi 9T?

Cost depends on the type of service and region: Type of service Cost (ruble) Term Guarantee Official service Xiaomi 2000-2500 3-7 days 6-12 months Informal service 1000-1500 1-2 hours 1-3 months Self-replacement 800-1200 (part only) 1-2 hours No Prices are relevant for 2026. The cost of official replacement includes diagnosis and configuration of the power controller.