Xiaomi Redmi Note 9 battery check: a complete guide with secret codes and applications

Why it is important to monitor the battery status of the Redmi Note 9

Xiaomi Redmi Note 9 has a 5020 mAh lithium polymer battery that degrades over time, even when used carefully. After 300 to 500 full charge cycles, the capacity can drop by 20 to 30 percent, leading to rapid discharge, sudden blackouts and overheating. But how do you know exactly how worn out your device’s battery is?

In this article, you will find 5 proven ways to diagnose a battery, from built-in MIUI tools to hidden engineering menus and third-party applications. We will also reveal the secret code ##4636##, which shows the real state of the battery without root rights, and explain how to decipher technical parameters like voltage, temperature and health.

Important: The methods work on all Redmi Note 9 modifications (including Note 9 Pro, Note 9S and Note 9T), but some features may vary depending on the MIUI version (for example, MIUI 12-14 changed the path to battery settings).

Method 1: Checking through standard MIUI settings

The easiest way is to use the built-in MIUI statistics, which won't show the exact percentage of wear, but will help you estimate the operating time and identify anomalies.

Instructions:

• 📱 Open the Settings. → Battery and productivity → Battery utilization.
• 📊 Scroll down to the Battery Statistics chart – this shows screen time and total charge consumption.
• ⚡ Click on the Three Dots icon (top right) and select Battery Statistics".

What to analyze:

• 🔋 Capacity in mAh: If the value is significantly below 5020 mAh (e.g. 4200-4500), the battery is worn out.
• ⏱️ Operating time: when you use it actively (social networks, video), the smartphone should keep a charge of 8-12 hours.
• 🌡️ Temperature: Normal range - 25–40°C. Exceeding 45°C indicates degradation or malfunction.

Battery use by application|Discharge schedule for the last 24 hours|Battery temperature|Operation time from one charge-->

⚠️ Attention: B MIUI 14 Battery Statistics may be hidden. If it is not available, update your firmware or use alternative methods (see below).

Method 2: Secret engineering codes for diagnostics

Hidden service menus provide accurate data on battery status, including voltage, temperature and wear. The following codes are used for the Redmi Note 9:

How to use:

1. Open the phone app.
2. Enter the code (e.g. #4636##) and the menu will open automatically.
3. Go to the tab "Battery Information".

Decoding of key parameters:

• 🔌 Level: current percentage of charge.
• 💡 Health: battery status. Good is normal, Unknown or Dead is critical wear.
• ⚡ Voltage: voltage. Normal: 3.7-4.2 V.
• 🌡️ Temperature: Temperature in tenths °C (e.g, 325 = 32.5°C).

Standard settings MIUI| Engineering codes |AccuBattery |Never checked-->

Method 3: Applications for deep diagnostics

Standard MIUI tools provide limited information, and for detailed analysis, we recommend using third-party utilities:

1. AccuBattery (free, no root)

Shows:

• 📉 Real battery capacity (compared to factory).
• 🔄 Number of charging cycles.
• ⚡ Discharge speed in mA/h.
• 📊 History of use.

How to use:

1. Install AccuBattery from Google Play.
2. Charge your smartphone to 100% and wait for calibration (1-2 cycles).
3. Go to the Health tab - here you will see the percentage of wear.

2. CPU-Z (free, technical data)

It displays:

• 🔋 Current capacity in mAh.
• 🔌 Battery technology (Li-Po, Li-Ion).
• 📱 Battery manufacturer (e.g, ATL or SDI).

⚠️ Note: Apps like AccuBattery require multiple charging cycles for precise calibration!

💡

If AccuBattery shows a capacity below 4000 mAh at 0% wear, reset the statistics in the application settings and complete the full discharge / charge cycle (0–100%).

Method 4: Checking through ADB (for advanced users)

If you want the most accurate data, use ADB (Android Debug Bridge), which requires a PC connection, but shows hidden options that are not available in the standard menu.

Instructions:

1. Install ADB Tools on your computer.
2. Enable USB debugging on your smartphone: Settings → About Phone → MIUI Version (click 7 times) Settings → Additional → For Developers → Debugging on USB
3. Connect Redmi Note 9 to your PC and execute the command: adb shell dumpsys battery

Key parameters in the conclusion:

• Capacity: X is the current capacity in %.
• Voltage: X is the voltage in microvolts (divided by 1000 for volts).
• temperature: X is the temperature in tenths of °C.
• Technology: Li-poly is a type of battery.

💡

ADB shows raw data from the battery controller, without rounding and embellishment by MIUI. This is the most accurate method, but requires technical skills.

Method 5: Visual Diagnostics and Physical Examination

Sometimes the state of the battery can be determined without programs - by external signs:

• 🔥 Bloating: If the back cover or screen starts to "go away", immediately turn off the smartphone.
• ⚡ Fast discharge: If the charge drops from 50% to 0% in 10-15 minutes, the battery needs to be replaced.
• 🔌 Charging problems: The smartphone does not recognize the charger or only charges in a certain position of the cable.
• 🌡️ Overheating: If the phone is heated without load (e.g., in standby mode), it is a sign of degradation of elements.

How to check for bloating:

1. Put your smartphone on a flat surface (screen up).
2. Lightly press the center of the back cover – if it “plays” or bends, the battery is swollen.
3. Light the flashlight on the side: if there is a gap between the case and the screen, it is 100% bloating.

⚠️ Attention: A bloated battery may ignite when mechanically exposed or overheated. Don't try to open it - contact the service center!

Table: Standards and critical state of the battery

If you're in the Critical State column, you need to replace the battery. For the Redmi Note 9, the original battery costs 1,500-2,500. ₽, Replacement in the service – another 1000-1500 ₽.

FAQ: Frequent questions about the Redmi Note battery 9