Xiaomi Mi 8 is the flagship of 2018, which is still relevant thanks to the powerful hardware and support for custom firmware. But even the most reliable smartphone over time faces battery degradation: reduced capacity, increased charging time, and autonomy drops by 30-50% after 2-3 years of active use. How to know how worn out the battery of your Mi 8 without disassembling the phone? In this guide, 5 proven methods with step-by-step instructions, regulatory values and diagnostic tips.
We will examine both software methods (through hidden menus, apps, and ADBs) and indirect signs of wear that can be seen without special tools. We will focus on the unique engineering menu codes for the Mi 8 that do not work on other Xiaomi models, and you will learn how to distinguish real wear and tear from temporary system failures and when it is time to change the battery.
1. Check through the engineering menu (#4636##)
The fastest way to get data about the battery is to use the hidden engineering menu available on all Android devices. On the Xiaomi Mi 8, it opens through a special code, but there are nuances: some items may be missing or display incorrect data due to the MIUI shell.
To open the menu:
- Open the Phone app.
- Enter the combination: ##4636## (no spaces).
- In the window that appears, select Battery Information.
In this section you are interested in the following parameters:
- 🔋 Level of charge (level) – current percentage in numbers (may differ from the indicator in the status bar).
- 🔌 Power source – must be a battery (if connected to a charge – usb or ac).
- 📊 Status is the perfect option: Discharging or Charging. If Unknown is a sign of a controller failure.
- 🔥 Temperature – Normal for Mi 8: 25–40°C. Exceeding 45°C critically!
- ⚡ Voltage – should be in the range of 3.7-4.2 V (on a fully charged battery).
⚠️ Warning: If the engineering menu displays Health: Unknown or Health: Dead, it means the system can't determine the battery status. It could be either physical wear and tear or a firmware failure.
Method limitation: the engineering menu does not show the actual battery capacity in mAh, only the current parameters.
2. Use of diagnostic applications (AccuBattery, CPU-Z)
Specialized applications provide more detailed information than standard Android tools. For the Xiaomi Mi 8, AccuBattery (for wear analysis) and CPU-Z (for checking technical parameters) are best suited.
AccuBattery: analysis of capacity and wear
This app tracks charging/discharge cycles and calculates the actual battery capacity compared to the factory (3400 mAh for the Mi 8).
- Install AccuBattery from Google Play.
- Charge your phone to 100% and disconnect from the network.
- Use your smartphone until it is completely discharged (until it is automatically turned off).
- After charging to 100%, open the Health tab in the app.
In this section you will see:
- 📉 The estimated capacity is the actual battery capacity per mAh. For example, if you show 2800 mAh, the wear is ~18%.
- 🔄 The number of charging cycles, the more, the more degradation. For the Mi 8, the critical threshold is 500.+ cycle.
- ⚡ Discharge rate - in mA / h. Norm in standby mode: 50-100 mA / h.
AccuBattery also shows a temperature chart that helps detect overheating, and if the battery is regularly heated above 40°C, it accelerates wear by 2-3 times.
CPU-Z: Technical parameters of the battery
CPU-Z provides low-level battery information, including:
- 🔋 Technology: The Mi 8 should be Li-ion.
- ⚡ Voltage – Compare with data from the engineering menu.
- 📊 Charge level in percentage and volts.
⚠️ Attention: If in CPU-Z If you see a 0 mAh or Unknown capacity, it may indicate damage to the battery controller, and you need to be diagnosed at the service center.
The advantage of apps is that they keep statistics and allow you to track the dynamics of wear, for example, if the capacity fell from 3200 mAh to 2500 mAh in six months, it is time to change the battery.
Charge your phone to 100% | Turn off battery optimization for AccuBattery in MIUI settings |Do not connect charging during the test | Use your phone to full discharge (0%) | Repeat cycle 2-3 times for accuracy-->
Verification through ADB (for experienced users)
If you want the most accurate data, you can use Android Debug Bridge (ADB), a debugging tool that allows you to get information directly from the system, which requires command line skills, but gives you access to parameters that are not available through applications.
Instructions for Xiaomi Mi 8:
- Enable Developer Mode: Go to Settings → About Phone. 7 times click on MIUI Version. Return to Settings → Additional → Developer. Activate Debugging over USB.
Connect your phone to your PC via USB (use the original cable!).
ADB Tools
Win + R → cmd
cd C:\path\pad\platform-toolsadb shell dumpsys batteryIn the conclusion of the command, pay attention to the following lines:
| Parameter | Example of meaning | What does it mean? |
|---|---|---|
| level | 85 | Current charge in % (may differ from MIUI indicator) |
| voltage | 3987 | Voltage in millivolts (3987 mV = 3.987 V). |
| temperature | 308 | Temperature in tenths of °C (308 = 30.8 °C). |
| health | 2 (Good) | Condition: 2 - good, 3 - average, 4 - bad. |
| cycle count | 214 | The number of full charging cycles. |
The key is health. If it's 4 or 7 (Dead), the battery needs to be replaced. Also, pay attention to cycle count: 500+ typically drops below 70% of the factory capacity.
⚠️ Note: If the adb shell dumpsys battery returns a permission denied error, do the following first: adb shell su dumpsys battery (root rights required).
ADB-This method is suitable for deep diagnostics, but takes time to adjust. If you are not sure about your skills, use the applications from method 2.
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Before using ADB, disable all background apps on your phone – they can distort your energy consumption data.
4. Indirect signs of battery wear
You don't always have the tools to check it out, and you can tell how your battery wears by the behavior of your phone, and you can see the following symptoms:
- ⚡ Fast discharge – if the Mi 8 discharges in 3-4 hours with moderate use (previously kept a day), the capacity fell by 40-50%.
- 🔌 Uneven charging – the phone freezes 80-90% or jumps from 50% to 100.
- 🔥 Overheating – if the body heats up even with a simple scrolling of the tape in social networks, the battery has degraded.
- 📉 Spontaneous shutdowns – the phone shuts down at 15-30% of the charge, although it used to work up to 0%.
- 🔋 Battery bloating – if the back cover of the Mi 8 starts to bulge or there is a gap between the screen and the body, immediately turn off the phone!
The last point is particularly dangerous: a bloated battery can damage the screen or even ignite. If you notice a deformation of the case, do not try to charge the phone - contact the service to replace the battery.
Another indirect sign is charging time: the new Mi 8 battery charges to 100% in 1.5-2 hours (with the original RAM), if the process is stretched for 3-4 hours, this indicates increased internal resistance of the cells.
What if the phone turns off at 15-20% charge?
5. Secret codes for Xiaomi Mi 8
The Xiaomi Mi 8 supports several unique service codes that allow you to get data about the battery, which is not available through the standard menus. These codes only work on the Mi 8 and some other Xiaomi models based on the Qualcomm Snapdragon 845.
List of useful combinations:
- 🔢 ##6484## - Battery test (shows voltage, temperature and condition).
- 🔢 ##64663## - Menu testing hardware components, including battery.
- 🔢 ##4636## - Standard Engineering Menu (Battery Information).
- 🔢 ##284## - Battery test (does not work on all firmware).
After entering the code ##6484##, you will see a screen with the following parameters:
- MB_06 — battery voltage in millivolts.
- MB_Temp — temperature.
- Charging is the status of charging (Enabled or Disabled).
If a Connection problem or Invalid MMI code message appears after entering the code, it means:
- The code is not supported by your version of MIUI.
- The phone is blocked by the operator (for example, if you bought on credit).
- A custom firmware has been installed that has removed service menus.
⚠️ Note: Do not enter random codes on the Xiaomi Mi 8! Some combinations (e.g. ##7780##) can reset settings or erase data.
Secret codes are easy to verify quickly, but don't provide as much detail as ADB or AccuBattery. Use them as an additional tool.
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On the Xiaomi Mi 8, code ##6484## often shows more accurate battery data than the standard engineering menu.
The rules of wear and when to change the battery
Even if the Mi 8 battery is held, its capacity is gradually reduced. Here are the standard wear and tear indicators for lithium-ion batteries:
| Level of wear and tear | Residual container | Signs. | Recommendations |
|---|---|---|---|
| 0–20% | 80–100% | It’s almost like a new phone. | Keep using, keep track of the temperature. |
| 20–40% | 60–80% | The phone is discharged 20-30% faster than before. | Calibrate the battery every 3 months, avoid overheating. |
| 40–60% | 40–60% | The charge lasts 4-6 hours, spontaneous shutdowns are possible. | Prepare to be replaced, avoid deep discharges. |
| 60%+ | Less than 40% | The phone discharges in 2-3 hours, warms, swells. | Immediate replacement, risk of damage to the phone. |
For the Xiaomi Mi 8, the critical threshold is 50% wear (residual capacity ~1700 mAh).
- Autonomy in standby mode is reduced to 8-12 hours.
- The phone can shut down at 10-15% charge.
- Charging takes 3+ hours.
If you plan to use the Mi 8 for another 1-2 years, replace the battery with 30-40% wear and tear, which will prolong the life of the phone and protect other components (such as the power controller) from increased load.
Cost of replacing the battery with Xiaomi Mi 8 (2026):
- Original battery: ~1500-2000 rubles.
- Analogue (quality): ~ 800-1200 rubles.
- Work in the service: ~500-1000 rubles.
When replacing, choose batteries labeled BLC11 (original) or proven ATL or Sunwoda counterparts. Avoid cheap Chinese batteries without certification - they can swell in 2-3 months.