How to check the battery on Xiaomi Redmi Note 8: from the code *#*#4636#*#** to disassembly

Xiaomi Redmi Note 8 with its capacious battery of 4000 mAh has long been a popular favorite, but even the most reliable battery eventually degrades. If your smartphone starts to run out in half a day, turn off at 20% charge or overheat during charging are sure signs of battery problems. In this article, we will discuss 6 working ways to check the battery: from hidden engineering menus to disassembling the case with a multimeter.

It's important to understand that the Redmi Note 8 (codenamed ginkgo) has a lithium polymer battery that loses up to 20 percent of its capacity after 500 full charge cycles, and can deliver 100 percent of its charge, even though it's only 60 percent of its actual capacity, and we'll teach you how to distinguish software glitches from physical wear, and we'll also give you a checklist to prevent further degradation.

1. Check through the engineering menu (#4636##)

The fastest way to get data about a battery is to use a hidden engineering menu, which is available without root rights or additional applications.

##4636##

After that:

• 📱 Select Battery Information (Battery Information).
• 🔋 Note the parameters: Level - current percentage of charge (should coincide with the indicator in the status bar); Voltage - voltage in millivolts (normal for Redmi Note 8: 3700-4300 mV); Temperature - temperature (optimum: 25-40°C).
• ⚠️ If the voltage is below 3500 mV at 20% charge, the battery is critically worn out.

Important: Some MIUI firmware may not have Battery Information, in which case use the alternative code ##6484## or move on to the next method.

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If the engineering menu does not open, check if access to it is disabled in the developer settings (Settings → About Phone → MIUI version – tap 7 times to unlock).

2.Diagnostics through applications (AccuBattery, CPU-Z)

Third-party utilities provide more detailed information, including the actual battery capacity and the number of charging cycles.

AccuBattery (recommended)

Download AccuBattery from Google Play. After installation:

• 🔄 Calibrate the app: fully discharge the phone before turning off, then charge to 100% without interruptions.
• 📊 Go to the Health tab. It'll show up here: 🔋 Design capacity (e.g., "3200 mAh out of 4000 mAh" means wear by 20 mAh%). 🔄 Number of charging cycles (more than 500 cycles – a reason to replace).

CPU-Z

The CPU-Z shows the battery technical details in the Battery section:

• 📋 Health – state ("Good" or "Unknown").
• 🔌 Technology - Type of battery (should be Li-polymer).
• 🔢 Capacity - current capacity (compare with passport 4000 mAh).

⚠️ Attention: If in CPU-Z If you see a capacity above 4,000 mAh, that's a calibration error on the controller, you need to reset the battery statistics through the Settings. → Battery → Three points. → Reset.

Install only one diagnostic application (data conflicts are possible)

Disable battery optimization for the selected utility in MIUI settings

Charge your phone to 100% before the first test

Do not use your phone actively during calibration.-->

Visual inspection of the battery (during disassembly)

If the software methods show critical wear, you should visually inspect the battery.

• 🔧 Plastic blade or mediator.
• 🔥 Fryer (for softening glue).
• 🛠️ Suction (optional).

Disassembly algorithm:

1. Turn off the phone and remove the tray. SIM-map.
2. Heat the back cover around the perimeter with a hair dryer (temperature not higher than 60 ° C).
3. Carefully tuck the lid with a spatula, starting at the bottom corner.
4. Disconnect the battery plume (it is under the protective film).

Signs of a faulty battery:

⚠️ Warning: If the battery is swelling, don't turn on the phone or try to puncture it! Lithium polymer batteries can ignite if damaged. Use protective gloves and glasses when disassembling.

4. Multimeter test (for advanced users)

The multimeter measures the actual voltage and internal resistance of the battery.

1. Take your phone apart (see the previous section).
2. Transfer the multimeter to DC voltage measurement mode (DCV, limit 20V).
3. Connect the probes to the contacts of the battery: red - "+", black - "-".

Normal performance for the Redmi Note 8:

• 🔋 4.2–4.3V — 100% charge.
• 🔋 3.7–3.8V — 50.
• 🔋 Below. 3.5V — Deep discharge (requires special ROM to restore).

To check the internal resistance:

1. Transfer the multimeter to resistance measurement mode (200Ω).
2. Connect the probes to the contacts.
3. Normal: 50–200 mΩ. If the resistance is above 500 mΩ, the battery is worn out.

Engineering menu |AccuBattery |Visual inspection |Multimeter |Not checked-->

5. Verification through ADB (technical)

If you want the most accurate data from the battery controller, use Android Debug Bridge (ADB), a method that requires a PC and a developer mode enabled.

Instructions:

1. Turn on USB Debugging in Settings → About Phone → MIUI Version (stick 7 times) → Additional → For Developers.
2. Connect your phone to your PC and execute the command: adb shell dumpsys battery
3. Look for the lines: capacity: X - current charge in %. voltage: X - voltage in microvolts (divided by 1000 for volts). temperature: X - temperature in tenths of °C (for example, "250" = 25.0 °C). health: X - state (2 = "good", 3 = "bad").

Example of output for a worn-out battery:

health: 3




Voltage: 3650000 (3.65V at 30% charge – critically low!)




temperature: 450 (45°C)

⚠️ Attention: Teams ADB It may vary depending on the version MIUI. Some firmware requires root rights to obtain complete data.

6. Indirect signs of battery failure

Even without tools, you can suspect problems with the behavior of the phone:

• 🔌 Fast discharge (less than 4 hours in standby mode).
• 🔥 Overheating when charging or playing (above 45)°C).
• ⚡ Charge jumps (e.g., from 50% to 20% per second).
• 🛑 Spontaneous shutdowns at 15-30% charge.
• 🐢 Slow charging (more than 3 hours to 100%).

If you see at least 2 of these symptoms, the probability of battery wear is greater than 80%.

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On the Redmi Note 8, the most common reason for fast discharge is not battery wear, but application background activity. Before diagnosing the battery, check the consumption in Settings → Battery → Use and disable unnecessary services.

Frequently asked questions