Why is it important to monitor the battery status of the Mi 8?
The battery is one of the most vulnerable components of the smartphone, and the Xiaomi Mi 8 (released in 2018) is no exception. Over time, battery capacity inevitably declines: after 300 to 500 charging cycles, you may notice that the phone is discharged 20 to 30% faster than before. But how do you know that the problem is in the battery, and not in the background or in a malfunction of the charger?
In this article, we will look at 7 working ways to test the battery, from built-in MIUI tools to engineering codes and third-party applications. You will learn what is considered normal for the Mi 8 after 3-5 years of operation, how to distinguish software failure from physical wear, and what to do if the capacity has fallen below a critical 70%.
Warning: If your Mi 8 suddenly shuts down at 15-30% charge, warms up while charging, or the body swells, these are emergency signs.
1. Built-in diagnostics in MIUI: quick inspection
The easiest way to assess battery health is to use standard MIUI tools, which will not show the exact capacity in mAh, but will help to identify anomalies in energy consumption.
How to open statistics:
- 📱 Go to Settings. → Battery and productivity → Battery utilization.
- 📊 Scroll down to the “Battery Use” chart – here you can see applications that consume power.
- ⏱️ Note the "Screentime" and "Stop Time" Norm for the Mi 8: 5-7 hours of active screen at medium load.
What should alert you:
- ⚠️ Sharp discharge jumps (e.g., 80% to 50% in 10 minutes) – a sign of a controller malfunction or physical wear and tear.
- ⚠️ High temperature (above 40)°C) during charging or playing - the battery may be bloated.
- ⚠️ Constant consumption of 1-2% per hour in sleep mode – indicates background processes or “voracious” applications.
The limitation of the method: the built-in MIUI statistics do not show the actual battery capacity, but only approximate consumption data.
2. Hidden engineering codes: data directly from the controller
The Xiaomi Mi 8 (like many Android smartphones) has hidden menus that display technical information about the battery, which run without root rights and do not require additional applications to be installed.
Instructions:
- Open the Phone app.
- Enter the combination: ##4636###.
- In the menu that opens, select "Battery Information".
What parameters are important:
| Parameter | Normal for Mi 8 | What does deviation mean? |
|---|---|---|
| Charge level (Level) | Corresponds to the percentages on the screen | Difference of more than 5% - calibration failure |
| Voltage (Voltage) | 3.7-4.2 V (at 100% charge) | Below 3.5 V - deep discharge, above 4.3 V - recharge |
| Temperature (Temperature) | 25-35°C (at rest) | Above 40°C - risk of degradation, below 0°C - possible loss of capacity |
| Technology (Technology) | Li-ion or LiPo | Any other value is a controller error |
⚠️ Warning: If the menu doesn't open after you enter the code, check if your carrier is blocking it. In this case, try the alternative code: ##284## (battery test).
What to do if the engineering menu is not opened?
3. Diagnostic applications: AccuBattery, CPU-Z and others
The utility side provides more detailed information than standard MIUI tools. We tested 5 popular apps and selected those that work exactly on the Xiaomi Mi 8.
Top.-3 battery-testing:
- 🔋 AccuBattery shows real capacity, wear and charging speed. Plus: runs without root, minus - requires calibration (2-3 charging cycles).
- 📊 CPU-Z — Battery displays voltage, temperature and health (Health) free of charge, no ads.
- 🛠️ Battery Guru monitors charging cycles and warns of overheating.
How to use AccuBattery (Step-by-step):
Charge the phone to 100%|Open AccuBattery and wait for calibration (1-2 minutes)|Discharge your phone to 15-20% without recharging|Check the Health section to assess wear-->
What do the indicators in AccuBattery mean:
- Design capacity: original capacity of the Mi 8 is 3400 mAh. If the actual capacity is below 2500 mAh, the battery is critically worn.
- Wear: up to 20% is normal, 20-40% is required to be replaced in the near future, above 40% is an urgent replacement.
- Charging speed: The Mi 8 is 15–18 watts (Quick Charge 4.0) and if it is below 10 watts, it is a cable or adapter problem.
⚠️ Attention: Some applications (e.g, 3C Battery Monitor requires root rights for accurate readings, and without them, they can show inflated capacitance values.
4. Verification through ADB: for advanced users
If you're not afraid of the command line, ADB (Android Debug Bridge) will give you the most accurate information about the battery, which works even on locked bootloaders and does not require root.
What you need:
- 🖥️ Computer with installed ADB Tools.
- 📱 Included debugging by USB on Mi 8 (Settings) → The phone. → Version. MIUI → 7 times press to unlock Developer Settings, then enable Debugging by USB).
- 🔌 USB-cable (preferably original).
Commands to check the battery:
adb shell
dumpsys batteryDecoding of key parameters:
| Parameter | Example of meaning | What does it mean? |
|---|---|---|
| level | 85 | Current charge in % |
| voltage | 3987 | Voltage in mV (3987 mV = 3.987 V) |
| temperature | 280 | Temperature in tenths of °C (280 = 28.0 °C) |
| health | 2 | Condition: 2 = good, 3 = bad, 4 = critical |
⚠️ Note: if the health parameter is 7, it means that the battery controller cannot determine its condition, 90% of the time it indicates a physical malfunction (bloating, chain break).
💡
If ADB issues a "device unauthorized" error, check your phone's USB debugging permission, sometimes helping to reconnect the cable or reboot both devices.
5. Visual inspection: when software methods are powerless
Some battery problems are not easily diagnosed, such as battery bloating, which is one of the most dangerous malfunctions that can cause screen damage or even fire. How do you detect it?
Signs of a bloated battery:
- 📏 Curvature of the body: the phone “opened” at the seams, the screen began to move away from the frame.
- 🔧 Crackling when pressed: if you hear squeaking when pressing on the back cover, it is gas released from the battery.
- 🔥 Overheating without load: the phone is warmed even in standby mode.
- ⚡ Spontaneous shutdowns: the smartphone turns off at 30-50% charge.
How to check:
- Place the Mi 8 on a flat surface (such as a table).
- Press the center of the back lid lightly, and if the phone is playing (bending and coming back), the battery is swollen.
- Illuminate the flashlight along the seams of the case - if a gap is visible, this confirms the deformation.
⚠️ Warning: If you find bloating, immediately turn off your phone and do not use it until you have replaced your battery.
💡
A bloated battery is not only a loss of capacity, it's also a risk of damage to the motherboard, and even if the phone is still working, it's cheaper to replace the battery than to repair it after a short circuit.
6. Battery calibration: When the phone lies about interest
Sometimes the problem is not wear, but incorrect calibration of the controller. For example, the Mi 8 can show 100% charge, but after 5 minutes it abruptly shuts down. This is treated by resetting the battery data.
How to reset calibration (2 ways):
- 🔄 Using Recovery: Turn off the phone. Click the power. + Volume up to enter Recovery. select Wipe & Reset → Wipe Battery Stats (some firmware may call it Battery Calibration) Reboot your phone and fully charge/discharge it 2-3 times.
Through the app
Battery Calibration
GSam Battery Monitor
⚠️ Important: calibration only helps with software failures, and if the battery capacity has been physically reduced (for example, from 3400 mAh to 2000 mAh), no reset will restore the previous autonomy.
When calibration is useless:
- If the phone shuts down at 0%, that’s normal (deep discharge protection).
- If the capacity in AccuBattery is less than 60% of the original.
- If the battery is swollen or deformed.
7. Professional diagnostics: when to contact the service
If all of these methods did not give a clear answer, or you suspect a hardware malfunction (for example, a short circuit in the power supply chain), it is better to contact the service center.
Diagnosis in the service includes:
- 🔧 Multimeter Testing: Measurement of Real Voltage and Current Under Load.
- 🔍 Visual inspection: looking for bloating, oxidation, or damage to contacts.
- 📊 Charging controller test: often the battery problems are not related to the battery itself, but to the power chip (for example, the battery is not related to the battery, BQ25890 Mi 8).
- 🔄 Flip-flashing EEPROM Batteries (if supported by the model).
Cost of services (average prices in Russia in 2026):
| Service | Price, ₽ | Term |
|---|---|---|
| Diagnostics of the battery | 300–500 | 10-20 minutes |
| Battery replacement (original) | 1 500–2 500 | 1-2 hours |
| Battery replacement (analogue) | 800–1 500 | 1 hour |
| Renovation of the supply chain | 2 000–5 000 | 1-3 days |
⚠️ Warning: When replacing the battery in unofficial services, require a warranty of at least 6 months and check to install the battery with the correct controller (for the Mi 8, this is the first time you have a battery). HB4166R3ECW or C36C). The mismatch can lead to rapid wear and tear or even fire.