The Xiaomi Mi 9, released in 2019, is still a popular flagship among users who appreciate performance and camera. However, after 3-4 years of active use, even the best battery loses up to 30-40% of capacity, leading to rapid discharge, sudden blackouts and overheating. If your smartphone runs out in half a day or turns off at 20-30% charge, it’s time to think about replacing the battery.
In this article, you will find a step-by-step guide to changing the battery to the Mi 9, taking into account all the nuances from choosing the original battery to properly assembling the body. We will also examine the unique feature of this model - the presence of graphite heat conductive film, which is easy to damage if you sloppy dismantle. If you have never disassembled a smartphone, do not worry: with proper preparation, the procedure will take no more than 40-50 minutes.
Signs that Xiaomi Mi 9 battery needs replacement
How do you know if the battery is the problem, not the software failure or the charger?
- 🔋 The smartphone is running out of power. 3-5 hours with moderate use (social networks, messengers, calls).
- 🔥 The body heats up strongly during charging or playing, even at room temperature.
- 📉 The percentage of charge “jumps”: for example, from 40% immediately drops to 15% after a reboot.
- ⚡ Charging is interrupted or is jerked (connected-disconnected) with a serviceable cable.
- 🛑 The device is switched off when 20-30% charge and not activated without connecting to the network.
If you know at least 2-3 items from the list, the diagnosis is obvious. For accurate verification, you can use applications like AccuBattery or AIDA64 that show the actual battery capacity. For example, if instead of the 3300 mAh declared, the application shows 2200-2500 mAh, the battery is worn out by 25-30% and must be replaced.
⚠️ Warning: Before replacing the battery, check if the problems are caused by a software failure. To do this, reset to factory settings via Settings → The phone. → If the discharge is fast after the reset, the battery is the problem.
What battery to choose for Xiaomi Mi 9: original vs analogues
The quality of the battery is not only the life of the battery, but also the safety of the device, and cheap, uncertified batteries can swell, overheat, or even ignite.
| Type of battery | Manufacturer | Capacity | Average price (2026) | Pluses | Cons |
|---|---|---|---|---|---|
| Original. | Xiaomi (Article MBJ4057) | 3300 mAh | 2500–3500 ₽ | Compatibility guarantee, optimal charging current, long service life | High price, risk of running into a fake |
| Certified analogue | ZMI, Baseus, Remax | 3300-3500 mAh | 1200–2000 ₽ | Good price/quality ratio, often exceeding original capacity | It can sit a little faster, not always perfect for size. |
| Budgetary analogue | Unnamed Chinese brands | 3000-3300 mAh | 600–1000 ₽ | Low price | High risk of bloating, short service life, possible charging problems |
We recommend you to stay on the original battery or certified analogues from ZMI/Baseus. Pay attention to the article - it must match the MBJ4057. Buy only from trusted sellers (for example, AliExpress Official Store, Beru, Messenger) to avoid counterfeiting.
- 📦 Presence of factory packaging with a hologram.
- 🔍 Conformity of the article and container on the label.
- 📏 Exact sizes (must match the original: 71.5 × 73.5 × 3.8 mm).
💡
Before buying a battery, check it for authenticity with the Xiaomi Authenticity Check app (available on Google Play). QR-packet.
Preparing for replacement: security tools and measures
Replacing the battery with the Xiaomi Mi 9 requires care and the right tools.
- 🔧 Screwdriver kit: cross-haired PH00 and a flat 1.5 mm (for the screws of the body), as well as a five-pointed Y00 (plume).
- 🧲 Suction cup for removing the back cover (can be replaced with a thin plastic card).
- 🔥 Hair dryer or thermal air station for softening glue (temperature not higher than 80)°C).
- 🩹 Plastic mediators (2-3 (p.c.) to separate the cover and the battery.
- 🧴 Isopropyl alcohol (90%+) glue-residue.
- ☠️ Gloves and safety glasses (the battery contains lithium, which is dangerous if damaged).
Also prepare the workplace:
- 🪑 Work at a table with good lighting.
- 📱 Put your smartphone on a soft substrate (such as a napkin) so as not to scratch the screen.
- 🔌 Disconnect your phone from the network and completely discharge (up to 0%) – this minimizes the risk of short circuit.
⚠️ Warning: Never use metal tools (knives, screwdrivers) to separate the battery, which can puncture the battery and cause fire. Only plastic mediators!
Turn off the phone from charging and discharge to 0%|Prepare tools (screwdrivers, sucker, mediators)|Cleaning the workplace of foreign objects|Wear gloves and protective glasses|Check the new battery for compatibility-->
Step-by-step: how to remove the back cover and get the battery
Now, to the most critical stage, follow the instructions carefully, any error can damage the plumes or the display.
Step 1 Heating and Removing the Back Cover
- Turn on the dryer at minimum power and evenly warm the back cover for 2-3 minutes, keeping it at a distance of 5-7 cm.
- Suction suction the bottom of the lid (near the USB-C connector) and pull up. If the lid does not lend itself, gently tuck it in with a plastic mediator.
- Once you have a crack, use the mediator to run around the perimeter, separate the lid from the body, and be careful, there are plumes of the fingerprint scanner underneath the lid. NFC-antennae!
Step 2: Disconnect the plumes and battery
- Unscrew 10 screws (they are different lengths - remember where you were!) Use a magnetic substrate to avoid losing them.
- Carefully unplug the plumes: 📱 Main display plume (at the top of the display). 🔋 Battery plume (black connector with red marker). 👆 Footprint scanner plume (thin, next to battery).
Check if there are any plugs left – if you skip this step, you can damage the motherboard during further disassembly.
Step 3: Remove the old battery
- Put the battery on a plastic mediator on either side and slowly pull it up. If it doesn't go away, heat it up for another 1-2 minutes.
- Under the battery you will see a graphite heat conductive film – it must be carefully separated and transferred to a new battery (it improves heat sink).
- Remove the glue residue from the case with isopropyl alcohol. Do not use acetone or solvents - they can damage the plastic!
What to do if the battery is swelling?
Installation of a new battery and assembly of the phone
Now that the old battery is gone, we're going to start installing a new one, and it's important to take your time and watch every step.
Step 1: Preparing a new battery
- 📏 Check if the new battery is the same size as the old one (should be identical).
- 🔥 Stick the graphite film to the back of the battery (if it was coming off the old battery).
- 🧴 Apply a thin layer of new glue (you can use bilateral scotch) 3M 9448A) hull-mounted.
Step 2: Installation and connection
- Carefully put the battery in place, making sure it fits tightly to the body.
- Connect the battery plume to the motherboard (the connector should click with a slight click).
- Make sure no wires are clamped or sticking out - this can lead to short circuits.
Step 3: Assembly of the hull
- Connect all the plumes in reverse order (first the fingerprint scanner, then the display).
- Twisting all screws, starting with the longest (usually they stand in corners).
- Press the back cover and warm it up with a hair dryer for 1-2 minutes so that the glue grabs.
⚠️ Warning: Don't turn on the phone right away after assembly! 10-15 So you have a minute to let the glue freeze and all the contacts fall into place, and then you plug the charger in and watch the charging process first. 30 minutes – if the battery starts to warm or swell, immediately turn off the phone and contact the service.
💡
The key to assembly is not to confuse the screws in length! The screws from the camera are longer than the screws of the case. If you screw a long screw into an undesignated place, you can damage the motherboard.
Calibration of the new battery and check of performance
Even if you have installed the original battery, it may not work well for the first few days. To make the new battery last longer, calibrate:
- Full discharge-charging cycle: 🔋 Charge your phone to 100% and hold on charging for another 1 hour. 📵 Discharge before automatic shutdown (0%). 🔌 Repeat charging to 100% without interruption.
- Install AccuBattery and check the actual capacity (should be close to 3300 mAh). Run the test in AIDA64 (Battery section) - the temperature should not exceed 40 °C when charging.
If after replacement the phone began to discharge or warm up faster, the following reasons are possible:
- 🔌 Flawed fit of battery plume (check connection).
- 🔥 Defect of the new battery (refer to the seller for a replacement).
- 📱 Software failure (perform reset settings).
All-night charge (keep the charge level in the range of 20-80%).
Use of cheap chargers (power should not exceed 18W for the Mi 9).
- Overheating (do not leave your phone in direct sunlight or in your car in the summer).-->
Frequent Mistakes and How to Avoid Them
Even experienced tycoons sometimes make mistakes when replacing a battery, and here are the most common ones and ways to prevent them:
| Mistake. | Effects of consequences | How to avoid |
|---|---|---|
| Use of metal tools to separate the battery | Puncture of the battery, fire, failure of the motherboard | Use only plastic mediators |
| Overheating of the body with a hairdryer (>80°C) | Melting plastic, damage to plumes, screen detachment | Hold the hair dryer at a distance of 5-7 cm, use minimum power |
| Incorrect installation of graphite film | Overheating of the processor, reduced performance, sudden shutdowns | Move the film carefully from the old battery or replace it with a new one. |
| Confused screws during assembly | Damage to the motherboard, a broken camera or buttons | Sort the screws by length and mark their location |
If you have a problem after you replace your battery (phone doesn't turn on, doesn't charge, warms up), don't panic. 90% of the time, it's because:
- 🔌 Unconnected plume (check all connectors).
- 🔋 Defective battery (test it with a multimeter).
- 📱 Resetting settings BIOS (sometimes need to re-flash).
If you are not sure of your abilities, contact the service center. The average cost of replacing the Xiaomi Mi 9 battery in the workshops is 1500-2500 ₽ (battery-free).