Redmi Note 9 smartphones are famous for their autonomy due to the battery capacity of 5020 mAh, but over time, any lithium-ion power source degrades. Users often notice that the device begins to discharge faster, suddenly turns off in the cold or shows surges in percentage of charge. Diagnosis of the battery condition becomes a critical procedure when the operating time ceases to meet the needs of the owner.
Unlike the iPhone, Android does not provide a single universal button to display the percent wear ("Health") in the standard settings menu. Xiaomi also hides this data from the average user to avoid unnecessary panic or, conversely, ignoring real problems. However, there are proven methods to access technical information about current, voltage and temperature.
In this article, we will discuss all available methods of verification, starting from simple ones. USSD-You'll learn to distinguish between a software calibration failure and physical cell death, and the precise data will help you decide whether to reset the settings or whether it's time to change the battery.
Use of the Engineering Menu through USSD-code
The fastest way to access hidden diagnostic data is to use a special code that activates the engineering menu. On Redmi Note 9 smartphones with a MIUI shell, this method often works out of the box without requiring root rights. You need to open the Phone application and enter the character combination.
Enter the code ##6485##. If the system supports direct output, a window will open on the screen with technical data. Note that the latest character set can occur automatically, and a separate call button is not required. MB_06 (battery status; and MF_05 (capacity).
⚠️ Note: Some global versions of the firmware MIUI 12 and later, this code can redirect to the standard Help and Feedback menu or simply not respond. This is not a device error, but a limitation of the software of the region.
If the code didn't work, try an alternative path through the settings. Go to Settings. → The phone. → All parameters. You need to press quickly. 7-10 once on the line "Kernel Version" or "Version" MIUI", to activate additional options, although on modern versions of Android this method becomes less effective for accessing the battery.
Analysis of parameters in the engineering menu
Suppose you were able to open the diagnostic menu with a code ##6485##. You'll see a list of acronyms that can confuse an untrained user. MB_06. If it says “Good” next to it, the battery controller has not detected any critical errors and the chemical wear is within the acceptable limits.
The more important indicator is MF_05, It shows the current actual battery capacity in milliamp hours. 9 nominal capacity 5020 Comparing the value MF_05 And you can calculate the percentage of residual capacity, for example, if it says, 4000, wear is about 20%.
It is also worth paying attention to the parameter. MB_00, the current level of charge in percentage, and MF_02 — The total capacity is calculated. MF_02 and MF_05 This may indicate that the controller is out of sync. MF_05 down MF_02, A calibration procedure may be required.
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Parameter MF_05 It shows the actual capacity right now, and MF_02 — This is the calculated value of the total capacity, which may be incorrect without a full calibration.
Don't ignore the temperature. MB_01 or MF_04 (The menu version displays the battery temperature. 20 before 40 Celsius in active operation, if the temperature is higher in simple 45 degrees, this is a signal of possible internal short circuit or degradation of the electrolyte.
Checking through the hidden test menu of CIT
MIUI firmware also has a customized CIT (Customer Integration Test) service menu for factory testing of components, which can be accessed via code ##64663## or through the Service & feedback app, if installed, which allows for in-depth diagnostics.
In the CIT menu, select "Battery Indicator" or "Battery Test." The system will run an automatic test that will check the voltage, current and battery response to the load. Unlike the static data in the engineering menu, this is a dynamic check. The device can ask you to discharge the battery to a certain level or, conversely, charge it.
- 🔋 Battery Status: Shows Current Status (Charging, Discharging, Full).
- 🌡️ Temperature: displays real-time heating with high accuracy.
- ⚡ Voltage: voltage at terminals important for assessing internal resistance.
- 📉 Level: Logical charge level visible to the user.
If the system produces a "Battery communication error" or "Battery voltage low" error in the CIT test, it often indicates a physical malfunction of the plume or the cell itself, in which case the software recovery methods will not help, and interference with the hardware is required.
What happens if the CIT menu doesn’t open?
Use of third-party applications for diagnosis
When Xiaomi's built-in tools are unavailable or show scant information, specialized applications from the Google Play Market come to the rescue, led by AccuBattery, which not only reads data, but also analyzes the charging process, calculating the actual capacity based on injected current.
It's important to understand how these snails work. They don't know the factory capacity of your Redmi Note 9 out of the box. The app should accumulate statistics over several charging cycles (usually 2 to 5 full cycles), only after that the data in the Health section will become reliable.
Other useful applications include Cpu-Z and AIDA64. They provide detailed information on chemical composition, technology (Li-Po), voltage and temperature. In the Battery section of the Cpu-Z app, you can find the "Technology" field, which confirms the type of battery, and "Status", which shows whether the phone is charging.
☑️ Proper battery calibration
However, it is worth remembering that third-party software has limited access to Android system files without root rights. Charging cycle data (Cycle Count) is often hidden by the manufacturer.
Detailed analysis via ADB and Fastboot
For users who are ready to connect a smartphone to a computer, access to the deepest data through the Android Debug Bridge debugging (ADB). This method allows you to read the battery logs directly from the system, bypassing the interface constraints, USB-cable and installed drivers ADB.
First, activate the developer mode on Redmi Note 9. → About the phone and 7 times click on the "Version" MIUI". Then, in the menu "Additional" include "Debugging by" USB". Connect your phone to your PC and allow access on your smartphone screen.
In the computer command line, enter the following command to output complete battery information:
adb shell dumpsys batteryThis command will give you a list of parameters including the mAc (AC plugged), mUsb (USB plugged, mWireless and charge level. However, more informative will be the command to read the file logs of the kernel if there is root access, or use specialized ADB-Scripts that parse the output dumpsys and calculate wear.
| Parameter ADB | Description | Normal value. |
|---|---|---|
| level | Current % charge | 0-100 |
| scale | Maximum scale (usually 100) | 100 |
| status | Status (2=charging, 3=discharging) | 2 or 3 |
| voltage | Voltage in mV | 3700-4400 |
⚠️ Warning: Do not attempt to enter adb shell dumpsys battery set commands to change parameters if you do not understand their purpose. Resetting values may result in incorrect display of charge and the need for a complete reset of the device.
Visual signs and physical diagnosis
Software is good, but the physical condition of the Redmi Note 9 often speaks to the problem louder than any number. Lithium polymer batteries can swell when degraded. It's due to the release of gases inside the sealed shell. If you notice that the back of the smartphone has started to recede or the screen has risen on one side, this is a critical sign of bloating.
A bloated battery is a fire hazard, and it's strictly forbidden to operate such a device, and even if it's a software wear rate of 10 percent, physical bloating means that the chemical processes are out of control, and in this case, replacing the battery is the only safe solution.
Another sign is unstable behavior when the charge is low: if the phone turns off at 20-30%, and after connecting to the network immediately shows 50-60%, this indicates a high internal resistance of the cell, the voltage under the load falls below the minimum shutdown threshold, although the battery still has energy.
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Store your phone at 40-60% charge, unless you plan to use it for a long time. Full charge or complete emptying with long storage accelerates the degradation of battery chemistry.
Also note the heating in the upper part of the case (where the battery is located) during charging. Excessive heating (>45 ° C) at rest or under low load indicates aging of the battery or problems with the power controller on the motherboard.