How to change the battery on Xiaomi Mi 9: full instructions with photos and nuances

Why the Mi 9 battery fails and when to change it

The Xiaomi Mi 9, launched in 2019, is still popular with users thanks to its powerful hardware and triple-module camera. However, even the most reliable device faces battery degradation over time — battery capacity declines, the phone runs out in a few hours, and sometimes even shuts down at 20-30% charge. If your Mi 9 starts behaving the same way, it’s probably time to replace the battery.

According to service centers, the average lifespan of lithium polymer batteries in smartphones is 2-3 years of active use. After that, the capacity drops by 30-50%, and the charge controller starts to malfunction. In this article, we will discuss how to change the battery on the Xiaomi Mi 9 without damaging the board or display, what tools you will need and what to look for when choosing a new battery.

Before you start disassembling, make sure that the battery is the problem, and you can check this with apps like AccuBattery or the built-in menu ##4636## (Battery Information section), and if the actual capacity has dropped below 2500-2800 mAh (at the initial 3300 mAh), a replacement is inevitable.

What tools will be needed to replace

To carefully disassemble the Xiaomi Mi 9 and install a new battery, you will need a specialized set of tools. Without them, you risk damaging the plumes, tearing off contacts or scratching the body.

• 🔧 Plastic blades (spoogers) - for gently putting the lid and disconnecting the plumes!
• 🔨 The screwdriver. PH00 or T3 — The usual screwdriver will not work because of the risk of tearing off the slats.
• 🔥 A hair dryer or a thermo-air station to soften the glue under the battery. The temperature must not be higher than 80.°C, otherwise you can melt plastic parts.
• 🧲 Screen suction cup – will help lift the display module after heating the glue.
• 🔋 Isopropyl alcohol (90%+) — Removing glue residues and cleaning contacts.
• 📦 The new battery is only an original or certified analogue with a capacity of 3300 mAh and voltage 3.85V.

Also, prepare an antistatic bracelet, or at least discharge yourself by touching a metal object, which will save the board from static electricity. Work on a clean, well-lit surface, preferably with a foam or rubber substrate, so as not to scratch the glass.

How to choose a high-quality battery for Mi 9: original vs analogues

One of the most important things is choosing a new battery, and there are a lot of fakes on the market that not only fail quickly, but can swell or ignite.

• 🔍 Original battery from Xiaomi (article) MBJ405790) — Best option, but more expensive (about 2000-2500) ₽). Sold in branded service centers or on official sites.
• ⚡ Certified analogues of ZOP Power, CAMBAT Or Patona, cheaper (1200–1800 ₽), But check for the certificate. CE/RoHS customer reviews.
• ❌ No-name batteries with no labeling or suspiciously low price (less than 1,000) ₽) — They often have a real capacity of less than 2,000 to 2,500 mAh.

Before buying, check:

1. A holographic sticker with a serial number.
2. Production date – if the battery is more than 6 months old, its capacity has already decreased.
3. Coincidence of the connector and contacts with the original (on the Mi 9, a 4-pin plug is used).

Important: the battery for Xiaomi Mi 9 is incompatible with models Mi 9 SE, Mi 9T or Mi 9 Pro due to different sizes and connectors!

Step-by-step: how to disassemble Xiaomi Mi 9 and replace the battery

Now, to the most critical stage, the disassembly of the phone, follow the instructions carefully so as not to damage the plumes or the board.

Step 1: Turn off and prepare the phone

Turn off the Mi 9 and remove the tray for the SIM-Then heat the back cover with a hair dryer for 2-3 minutes, holding it at a distance of 5-7 cm. The glue under the lid will soften, and it will be easier to remove it.

Step 2: Removal of the back cover

Insert a plastic blade into the gap between the lid and the body (start at the bottom edge where the speakers are located). Carefully drive the blade around the perimeter until the lid detachs. Be careful - under the lid are the plumes of the fingerprint scanner and NFC-antennae!

Step 3: Battery disconnection

With a screwdriver, unscrew the 4 screws that hold the metal plate over the battery, then gently tuck the battery connector into a plastic blade and unplug it. Don't pull the wires!

Step 4: Remove the old battery

There's a tape underneath the battery, pick it up by a special tongue (usually black) and slowly pull it until the battery detachs. If the glue is too strong, warm it up again with a hairdryer. Don't use metal tools, you risk puncture the battery!

Step 5: Installation of a new battery

Check the contacts on the board, clean them with isopropyl alcohol if necessary, install a new battery, connect the connector and lock it with duct tape (usually included), and make sure the plumes are not bent.

Step 6: Build the phone

Put the metal plate back in place and twist the screws. Connect the fingerprint scanner and NFC plumes, then press the back cover. To fix it reliably, you can heat it up a little bit (no higher than 60°C) and press it down for 1-2 minutes.

Check that all plumes are connected | Make sure the screws are tightly twisted but without pulling | Clean the camera and speakers from dust | Charge the phone to at least 20% before first turning on-->

Calibration of the battery after replacement: why it is important

Once the new battery is installed, it needs to be calibrated so that the charge controller can correctly determine the charge level, and without calibration, the phone can show the wrong percentage or suddenly shut down.

How to do this:

1. Completely discharge the phone before automatically shutting down.
2. Connect the original charger and charge up to 100% without interruptions.
3. Turn off charging and use the phone as normal until it is completely discharged.
4. Repeat the charging-discharge cycle 2-3 times.

It is also recommended to reset the battery data via the engineering menu:

1. Enter the code ##4636##.
2. Go to the Battery Information section.
3. Press Battery calibration (if available).

If after calibration the phone still discharges quickly, check the background processes in the battery settings or perform a reset to factory settings.

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After replacing the battery, avoid using fast charging for the first 3-5 cycles, which will help the battery to get used to the new controller and prolong its life.

Frequent battery replacement errors and how to avoid them

Even experienced craftsmen sometimes make mistakes that lead to a phone breakdown, and here are the most common ones and ways to prevent them:

Another common problem is that the phone doesn't turn on after assembly, and there are many reasons.

• 🔌 Not connected to the display plume or battery.
• 🔋 The new battery is discharged “to zero” (you need to hold on charging for 10-15 minutes).
• 🛠️ Damaged fee during disassembly (requires diagnosis in the service center).

If the battery is discharged quickly after replacing, check the battery consumption in the settings (Settings → Battery → Battery Use).

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If the phone overheats or discharges quickly after the battery is replaced, it is likely that the problem is a non-original battery or a damaged charge controller, in which case contact the service center.

How much does it cost to replace the battery in the service center vs independently?

If you are not sure of your abilities, you can contact the official Xiaomi service or an authorized repair center.

Should you save money? If you've had experience disassembling the machine, it's cheaper to replace yourself, but if you've never had a phone screwdriver in your hand, you'd better trust the professionals to damage the board or the display at a cost that's many times more expensive.

In Moscow and St. Petersburg, the replacement of the battery with the Mi 9 offers many services. The average price in informal workshops is 1800-2200. ₽ In the regions, the cost may be lower (1500-1800) ₽), Make sure the master uses the original battery.

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Before contacting the service, check reviews on Yandex.Maps or 2GIS. Avoid workshops with a rating below 4.5 - there are often savings on spare parts.

FAQ: answers to frequent questions about replacing the battery with the Mi 9