How to see the battery capacity on Xiaomi Redmi Note 9: all working methods

Why it is important to know the actual battery capacity

Xiaomi Redmi Note 9 is equipped with a nominal battery capacity of 5020 mAh, but over time this figure inevitably decreases. Even with careful use after 1-2 years, the battery loses 15-20% of its original volume, which affects battery life. Checking the current capacity helps to assess the degree of wear and make a decision about replacing the battery.

The manufacturer does not provide direct tools to monitor battery health in the standard MIUI interface, but there are a few workarounds. In this article, we will look at all the current ways - from built-in functions to third-party utilities - and explain how to interpret the data. Importantly, the actual capacity below 80% of the factory is considered critical and requires a battery replacement.

Method 1: through the Engineering Menu (without root)

The Engineering Menu is a hidden MIUI section that contains technical information about the components of a smartphone, including the battery, and you don't need superuser rights to get there, but you need to enter a special code.

Open the phone application and type the combination:

##4636##

In the menu that appears, select Battery Information. Here you will see a few key options:

  • 🔋 Charge level – current percentage in digital form (e.g. 87%).
  • 📊 Status: Battery status (Good, Medium or Bad).
  • 🔌 Voltage – current value in millivolts (normal: 3700-4200 mV).
  • 🔄 Temperature - in degrees Celsius (optimum: 20-40)°C).

Unfortunately, the Redmi Note 9's engineering menu doesn't show the exact capacity in mAh, but you can indirectly measure wear by voltage and condition, for example, if the voltage is below 4,000 mV at 100% charge, it's a signal of battery degradation.

⚠️ Warning: Do not change the settings in the engineering menu unless you understand their purpose. Incorrect settings can lead to malfunctions in the smartphone.

Method 2: Using the AccuBattery application

AccuBattery (available on Google Play) is one of the most accurate battery monitoring solutions available, analyzing charging/discharge cycles and calculating real capacity from sensor data.

To get reliable results, follow the algorithm:

  1. Install AccuBattery and provide all the permissions requested.
  2. Charge your phone to 100% and disconnect from the network.
  3. Use your smartphone in normal mode until it is completely discharged (until it is automatically turned off).
  4. Connect the charger and wait for 100% charge.
  5. Open the app and go to the Health tab, and here you will find Estimated capacity.

Example: If the app shows 4200 mAh and the Redmi Note 9’s factory capacity is 5020 mAh, the wear is ~16%. AccuBattery also displays the number of full charging cycles and temperature statistics.

Charge the phone to 100%|Disable battery optimization for the application|Do not use ultrafast charging|Repeat the cycle 2-3 times for accuracy-->

Important: the first 2-3 cycles may give inaccurate data. Use the app for stable results for at least a week.

Method 3: through ADB-Teams (for advanced users)

If you are familiar with the Android Debug Bridge tool (ADB), You can get detailed information about the battery directly from the system, and this method requires you to connect the smartphone to the computer and install it. ADB-driver.

Sequence of action:

  1. Enable USB Debugging in the Developer Settings → About Phone → MIUI Version – Press 7 times, then go back to Additional Settings → For Developers.
  2. Connect the Redmi Note 9 to your PC and open the command line (or Terminal on macOS/Linux).
  3. Enter the command to check the status of the battery: adb shell dumpsy battery

In the conclusion, find the lines:

  • Level: 85 is the current charge in percentage.
  • Voltage: 3987 - Voltage in millivolts.
  • temperature: 305 - temperature in tenths of a degree (305 = 30.5 ° C).
  • charge_counter: 3500000 — current capacity in microamper-hours (divided into 1000, to get a mAh).

For example, charge_counter: 4200000 This means that the actual capacity is 4200 Compare this value to the factory (5020 mAh) for the assessment of wear.

⚠️ Attention: Use ADB Do not follow commands that you do not know the purpose of, which can disrupt the system.

Once a month | Every six months | Only when I notice a problem |Never-->

Method 4: Analysis with Mi Flash Tool (for firmware)

If you've ever flashed a Redmi Note 9 through the Mi Flash Tool, you'll notice that the process logs display battery information, a method that's only suitable for users familiar with smartphone firmware.

Algorithm:

  1. Connect your phone in Fastboot mode (clip Volume Down + Power when the device is off).
  2. Run the Mi Flash Tool and press Refresh to identify the device.
  3. In the program logs, find a line with the battery parameter. For example: battery: ok, 4500 mAh, 3.85V

This method gives a rough estimate, since the data is read at the time of connection and may not reflect the real capacity when fully charged, but it is useful for rapid diagnosis.

What if the Mi Flash Tool doesn’t show battery data?
If the logs are missing battery information, this could mean: 1. ADB/Fastboot drivers are installed incorrectly. 2. Battery is disconnected from the board (physical malfunction). 3. Mi Flash Tool version does not support your model. In such cases, use alternative methods from this article.

Table: Capacity standards for Redmi Note 9

Below is a table with recommended battery capacity values based on smartphone usage time, based on average degradation of lithium polymer batteries.

Time of useMinimum permissible capacity (mAh)Battery statusRecommendations
0-6 months4800–5020Excellent.Continue normal operation
6–12 months4500–4800Good.Watch the temperature when charging
1-2 years4000–4500SatisfactoryAvoid full discharge, calibrate the battery
2–3 years3500–4000Bad.Consider replacing the battery
More than 3 yearsLess than 3,500CriticalReplacement is needed

If the real capacity of your Redmi Note 9 is lower than the values from the table, it is a signal of premature wear, possible causes: the use of non-original chargers, frequent overheating or physical damage.

💡

To extend the life of the battery, avoid charging to 100% and discharging to 0%. The optimal range is 20-80%.

Frequent errors and myths when checking the capacity

When diagnosing a battery, users often encounter inaccurate data or misconceptions, including the most common:

  • ❌ Myth 1: "Play Market Apps Show Precise Capacity From Cycle One." Reality: Most utilities (including AccuBattery) require 3-5 full charge/discharge cycles to calibrate.
  • ❌ Myth 2: "If the phone is running out fast, it means the capacity has dropped." Reality: It could be the background activity of the apps or the wear of the processor. Check the battery consumption in Settings → Battery.
  • ❌ Myth 3: "Calibration of the battery (discharge to 0% and charge to 100%) restores capacity." Reality: Calibration only synchronizes the controller data with the real state, but does not increase physical capacity.

Another common mistake is using cheap testers (for example, the use of a tester, USB-These devices measure the flow of energy, not the actual capacity of the battery, and they are often overestimated by 10 to 15%.

💡

The only reliable way to find out the real capacity is specialized applications (AccuBattery) or ADB-Quick tests through the engineering menu only give approximate data.

Can I restore the battery capacity on the Redmi Note 9?
No, you can't physically restore the capacity of a lithium polymer battery, and the only way to get back to the original performance is to replace the battery with a new one, but you can slow down the degradation by following the guidelines: Use an original or certified charger. Avoid overheating (do not play heavy games while charging). Store your phone at 10–30 temperatures.°C.
Why does AccuBattery show a capacity higher than the factory capacity (for example, 5200 mAh)?
This is a calibration error that occurs if: You interrupted the charging/discharge cycle before it is completed; the battery controller gives incorrect data (for example, after resetting the settings); the application did not have enough statistics (use it for at least 3 days); to correct this, complete the full discharge/charging cycle 2-3 times in a row.
What percentage of battery wear is considered critical to replace?
Wearing over 20% (capacity below 4,000 mAh for the Redmi Note 9) is considered critical, but: Battery life is reduced by 30-40%. The phone can turn off at 10-15% charge. The battery heats up faster and charges longer. If the capacity falls below 3,500 mAh, replacement is required - further operation can lead to battery bloating.
Can I find out the battery capacity without installing applications?
Yes, but with limitations: Through the Engineering Menu (##4636##) — It shows voltage and condition, but not the exact capacity. ADB — It requires a connection to the PC, but provides data on the charge_counter. Through settings MIUI — The Battery section shows the flow graph, but not the capacity. ADB.
How much does it cost to replace the battery with the Redmi Note 9 in 2026?
The cost of replacement depends on the region and the service center: Original battery (from Xiaomi): 1500-2500 rubles. High-quality analogue: 800-1500 rubles. Budget analogue: 500-800 rubles. (low-resource risk). We recommend contacting authorized Xiaomi service centers or trusted workshops with a guarantee for work.