Full battery check Xiaomi Mi8: from *#*#4636#*#**** to disassembling the body

Why Xiaomi's battery Mi8 discharged too quickly?

Xiaomi Smartphone Mi8, The battery, which was released in 2018, is equipped with a 3,400 mAh lithium-ion battery, and even when used carefully, it can be reduced by 20 to 30 percent in 2-3 years, and in some cases, up to 50 percent. Mi8 Becoming discharged in half a day, turning off at 20-30% charge or overheating while charging, the problem almost certainly lies in the battery.

But how do you know for sure that it's the battery that's to blame, not the background, the power supply, or the damaged connector? In this article, we'll look at 5 working methods for checking, from hidden engineering menus to disassembling the device.

• 🔍 Check the battery wear using #4636## and MIUI Battery Health
• 📊 Evaluate the real capacity using AccuBattery applications and AIDA64
• 🔧 Identify physical defects (swelling, oxidation) without special tools
• ⚡ Calibrate the charge controller if the smartphone shows an incorrect percentage
• 🛠️ Prepare to replace the battery if the diagnosis showed critical wear

Important: Some methods require root rights or disassembly of the case, which can affect the warranty (if it still works), starting with the safest ways.

Method 1: Checking through the engineering menu (without root)

The fastest way to get basic battery information is to use a hidden engineering menu, which is available on all Xiaomi smartphones, including the one that is available on the phone. Mi8, It does not require additional programs.

Enter the combination in the phone application:

##4636##

Then the Test menu opens. Go to the Battery Information tab, and you're interested in three things:

⚠️ Note: If the Health field is blank or shows Unknown, it could mean:

• 🔋 Resetting of battery data (calibration required)
• 🛠️ Damage to the charge controller
• 📱 Unoriginal firmware (for example, custom LineageOS)

If the voltage at 100% charge is below 4200 mV and the temperature is above 45 mV°C Standby mode – battery needs replacement.

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To return to Health, try to fully discharge your smartphone before you turn it off, then charge it to 100% without interruption, sometimes helping to reset the controller errors.

Method 2: Applications for deep diagnostics

The engineering menu gives you limited data. Use specialized tools for detailed analysis. We tested 3 apps on Xiaomi. Mi8 And they chose the most accurate.

1. AccuBattery (free, no root)

Digibites' AccuBattery app shows real battery capacity, discharge rate and wear. Install it from Google Play and follow the following steps:

Charge your smartphone to 100%|Open AccuBattery and go to the Health section"|Click "Start monitoring"|Use your phone normally for 2-3 days|Check the value of "Design capacity" in mAh-->

Compare the resulting value with the original capacity of 3400 mAh:

• 🟢 3000-3400 mAh – battery in good condition
• 🟡 2500-3000 mAh - noticeable wear, it is worth thinking about replacing
• 🔴 Less than 2500 mAh – critical wear, high probability of sudden shutdowns

2. AIDA64 (paid version, no root)

AIDA64 provides detailed technical information, including data from the battery sensors:

1. Open the Battery section
2. Check the Capacity field for the project (3400 mAh) and Current Capacity
3. Pay attention to temperature and tension

⚠️ Attention: If in AIDA64 displays a capacity above 3400 mAh (e.g. 3600 mAh) - this is a controller error!

3. MIUI Battery Health (for firmware only) MIUI)

On smartphones with original firmware MIUI (including Mi8) There's a built-in diagnostic tool to open it:

1. Go to Settings. → The phone.
2. Tap 5 times on the line version MIUI
3. Enter password 123456 (if requested)
4. Choose Battery Health

This shows the percentage of battery wear, and if it's above 30 percent, we recommend replacing it.

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Applications show approximate data. Professional equipment is required for 100% accuracy (e.g., a tester). USB-C multimeter).

Method 3: Visual examination and physical tests

If the software methods show critical wear and tear, but you want to make sure 100%, you have to inspect the battery physically. Mi8 requires accuracy - the model has a fragile back cover and thin plumes.

Signs of a faulty battery (without disassembly)

• 📱 Bloating of the body: if the smartphone began to “splash” at the seams or the screen began to move away from the frame
• 🔥 Overheating: Battery heats up over 50°C even with a simple charge
• ⚡ Uneven charging: Percent jumps (e.g., from 50% to 20% per second)
• 🔌 Charging problems: the phone does not take charge or disconnects from the network

How to Disassemble Xiaomi Mi8 battery-examination

You'll need:

• 🔧 Plastic blade or mediator
• 🔥 Fryer (for softening glue)
• ⚡ Screwdriver. T4 (screw)

Step-by-step:

1. Turn off the phone and remove the tray for SIM-map.
2. Heat the back cover around the perimeter with a hair dryer (temperature 60–70)°C).
3. Carefully tuck the lid with a spatula, starting at the bottom corner.
4. Unscrew 10 screws. T4, metal-plate.
5. Disconnect the battery plume (it is under black insulation).

Examine the battery for:

• 🔋 Bloating (if the battery is "bubbled" - it needs to be replaced urgently!)
• 💧 Contact oxidation (green or white coating)
• 🔥 Traces of overheating (dark or deformed shell)

Method 4: Calibration of the charge controller

Sometimes the problem isn't with the battery itself, but with the charge controller that doesn't display the percentage correctly, like the smartphone shuts down at 30 percent, when it's actually 0%, and calibration will help.

Method 1 (without root):

1. Completely discharge the phone before turning off.
2. Connect the original RAM and charge for at least 8 hours (even if the indicator shows 100%).
3. Turn off the charging, turn off the phone and reconnect for 1 hour.
4. Repeat the cycle 2-3 times.

Method 2 (with root):

1. Install the Battery Calibration app.
2. Charge your phone to 100% and connect to your PC.
3. In the app, press Calibrate.
4. Reset the device.

⚠️ Attention: Calibration only helps when software fails, and if the battery is physically worn out, it won't restore capacity!

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After calibration, check the actual capacity through AccuBattery. If the value hasn't changed, the hardware is the problem.

Method 5: Test under load (stress test)

To identify hidden battery problems, run a stress test that will show how the battery behaves at maximum load.

Use the app. CPU Throttling Test (available on Google Play) Test algorithm:

1. Charge the phone to 100%.
2. Run the test and wait until the charge drops to 20%.
3. Take a look at the time and compare it to the norm. Mi8:

If the discharge occurs 2 times faster than normal, the battery needs to be replaced.

• 🌡️ Temperature: If it exceeds 60°C is an anomaly.
• 📉 Percentage jumps: for example, from 50% to 15% per minute.
• ⚡ Sudden shutdowns at 20–30% charge.

When is the time to change the battery Xiaomi Mi8?

Replacing the battery is inevitable if:

• 🔋 Real capacity on AccuBattery below 2500 mAh.
• 🔥 Temperatures are over 50.°C on standby.
• 💥 The body swelled or deformed.
• ⚡ The phone shuts down at 30-40% charge.
• 📉 Standby time reduced to 4-6 hours.

The cost of replacing the battery on Xiaomi Mi8 2026:

• 🛠️ Original battery (with warranty): 1500–2500 ₽
• 🔧 Analogue (quality): 800–1200 ₽
• 🏠 Self-sustained replacement: 500-800 ₽ (only if there is experience!)

⚠️ Note: When replacing the battery with Mi8 necessarily:

• Use the original glue for fixation (for example, B7000).
• Do not damage the antenna contacts on the back cover.
• After replacement, perform calibration (discharge / charge 2-3 times).

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Don’t skimp on battery quality! Cheap analogues can swell in 2-3 months or do not meet the declared capacity.

Frequent questions about Xiaomi battery Mi8