Declining smartphone autonomy is an inevitable process that affects every wearer sooner or later. When the Xiaomi Mi 8 stops living through the evening even with moderate use, and the percentage of charge jumps or the phone turns off by 20%, this is a sure sign of wear and tear of the lithium polymer battery. In such situations, the only right solution is a physical replacement of the battery, which allows you to return the device to factory performance without having to buy a new device.
The replacement procedure is not a trivial task for a beginner, since the design of the flagship 2018 involves the use of a large amount of glue to fix the components. You will need not only a new battery, but also a specialized set of tools, including suction cups, mediators and thermophen. It is important to understand that the rear cover of the Xiaomi Mi 8 is made of glass and glued around the perimeter, so the risk of damage if you open it neatly is extremely high.
Before you start taking action, you need to evaluate your skills and free time. Careless handling of plumes or violation of the temperature regime of heating can lead to failure of the display or motherboard. Below we will discuss in detail each step of the procedure to minimize the risks and ensure a quality result of recovery of your device.
To get started, you'll need to have a workspace that's well lit and the table surface is clean and free of unnecessary items so you don't lose small screws. It's also important to have a fastener sorting tank on hand, because the Mi 8 uses screws of different lengths, and messing them up can damage the internal components.
Tools and workplace preparation required
The quality of the repair depends on the tools used. Standard set of home tools will not be enough, since the design of the smartphone requires a delicate approach. You will definitely need a heating element, which can act as a professional thermophene, a conventional household heating pad or a special separator for screens.
Plastic blades (mediators) and a suction cup will be required to peel off the back panel. Metal tools are strongly discouraged from being used initially, as they can easily damage the glass or bite through the battery, and a set of screwdrivers including cross bits (usually PH00 or PH000) and possibly a five-pointed one (Pentalobe) if the screws at the bottom of the case are specific.
- 🔥 Thermophen or heating platform for softening glue.
- 🛠 A set of precision screwdrivers with a magnetic tip.
- 📱 Plastic mediators and a suction cup for opening the body.
- 🧴 Isopropyl alcohol and pipette for dissolving the glue layer.
Special attention should be paid to safety. Lithium batteries are always at risk of damage. If you accidentally puncture the battery shell with a needle or a sharp edge of a tool, there may be an ignition or even an explosion, so there should be good ventilation in the room, and a fire extinguisher or sand tank at hand for an emergency.
Before starting disassembly, be sure to turn off your smartphone. Even if the device does not respond to buttons, try to program shutdown via the menu. If the phone freezes and does not turn off, wait for the battery to completely drain before starting disassembly to avoid short circuit on the board when disconnecting contacts.
☑️ Checking readiness for repair
Removal of the rear glass panel
The most difficult and risky step is to separate the back cover from the frame of the body. Xiaomi Mi 8 uses an aggressive adhesive compound that securely fixes the glass. SIM-cards to provide air outlet and relieve internal pressure when heated.
Turn on the heater and set the temperature in the range of 80-90 degrees Celsius. Put the smartphone screen down on the soft fabric or silicone mat to avoid scratching the display. Warm up the perimeter of the back cover evenly for 3-5 minutes. Don't hold the hair dryer at one point for too long to not overheat the screen matrix, which can lead to yellow spots.
⚠️ Warning: Don't try to pull the lid while it's hot! Let the glue cool down a little during 30-60 But don't let it completely solidify again, and if you try to open it at the peak of the heat, it can cause the glass to burst from the temperature expansion.
After warming up, attach the suction cup to the bottom of the back, closer to the Mi logo, but not to the very edge. Carefully pull the suction cup upwards, creating a small gap. Insert a thin plastic mediator into the resulting gap immediately. Don't use force; if the lid doesn't move, return the phone to heat.
Move the mediator along the perimeter of the body, gradually cutting the adhesive layer. Exercise special care in the corners and in the area of the camera module, where the adhesive layer may be thicker. If you feel strong resistance, drip a little isopropyl alcohol into the gap, which will dissolve the adhesive and facilitate the process.
When all sides are free, gently lift the back cover. Don't make sudden movements, as a fingerprint scanner plume may be glued to the cover (if the model implies such a connection, although the Mi 8 scanner is often located separately, but there may be nuances with adhesive plume fixers).
What to do if the back cover is broken?
Dismantling the protective plate and disconnecting the plumes
When you take the back cover off, you'll see the inside of the smartphone, and most of the space is occupied by a black plate that covers the battery and the connections of the plumes, and this plate is screwed with a lot of screws around the perimeter and in the center.
Using a cross screwdriver, unscrew all the visible screws that hold this plate. Fold them into a separate cell, as they may differ in length from the screws of the case. Some screws may be hidden under stickers or seals - they must be gently pierced or removed. Once all the fasteners are removed, the plate should be easily removed.
Under the plate, you'll see the battery itself and the connectors connecting it to the motherboard. The first thing you need to do is turn off the battery. Find a wide plume that goes from battery to board. Carefully put a plastic blade or nail (if you have access) in the connector, but don't pull the wires.
- 🔌 Disconnect the main battery plume from the motherboard.
- 📱 Turn off the display and touchscreen plumes for complete power-off.
- 🔋 Check for additional camera module plumes.
- 🛡 Remove the vibro motor and speaker if they interfere with access.
After the battery is turned off, the device is completely de-energized, which makes it safe to operate, so you can remove the protective plate itself, if it's sitting tight, sway it slightly from side to side, make sure that no plume is pinched or pulled.
In some versions, this plate may be under the NFC module or antenna contacts. Be careful when removing, so as not to damage fragile elements. If you notice that a component is glued to the plate, carefully separate it before removing the protection.
Removing the old battery and installing a new one
The battery in the Xiaomi Mi 8 is also fixed with a glue layer, and it is quite durable. Just pull it out by the tongue (if it is present and not broken) is often impossible without the risk of damaging the battery.
Turn on the dryer and warm up the battery area through the open case for 2-3 minutes. The temperature should not exceed 60-70 degrees, so as not to damage the battery itself and nearby components. After heating, try to gently tamper with the edge of the battery with a plastic card or a thin mediator.
Move the tool under the battery, trying to dissect the adhesive layer. Don't use metal objects! If you feel the battery is beginning to deform or swell, immediately stop the pressure. In extreme cases, you can drip alcohol under the edge of the battery to dissolve the glue.
| Parameter | Old battery | New battery | Norma. |
|---|---|---|---|
| Capacity | Less than 2,500 mAh | 3300mAh | 3300mAh |
| Tension. | 3.7-3.8 Included | 3.85 In | 3.85 In |
| Status. | Bloating/Depreciation | Smooth, free of defects | Perfect. |
| Release date | Older 3 years | Fresh (up to 6 months) | Not older than 1 year |
Once the old battery is removed, clear the seat of glue residues. Use a plastic card and some alcohol. The surface should be flat and clean so that the new battery will fall tight and free of distortion. Check if there is any debris or glass shards inside.
The new BLP681 battery (a standard model for the Mi 8) is recommended to check with a multimeter before installation. The voltage should be in the working range. If all is well, apply a double-sided battery tape or a special glue B-7000 to the edges of the new cell in a thin layer. Insert the battery into the case and press tightly for a few seconds.
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Use a special glue B-7000 or T-7000 to fix the battery. Apply it with a thin layer around the perimeter, avoiding hitting the center where the controls are located, this will ensure reliable fixation and allow the battery to be replaced again in the future.
Assembly of the device and check of performance
Before the final assembly, you need to check if the new battery is working. Connect the battery plume to the motherboard. Press the power button. If the phone vibrates or the Mi logo lights up, success! You can not plug the screen yet, the main thing is to make sure that the board reacts.
If the phone is on, turn it off again, turn off the battery, and start installing the protective plate, put the plate in place and twist all the screws, make sure that no plume is squeezed and lies in its channels, especially carefully check the display plume.
Now you can apply a new adhesive layer to the back cover, clean the frame and the old glue cover with alcohol, stick a special adhesive frame (water resistant tape) around the perimeter, or apply a thin layer of glue, carefully combine the cover and press it around the perimeter.
For a reliable fixation, it is recommended to use rubber harnesses or stationery gums, wrapping them around the phone around the perimeter for 15-20 minutes, this will ensure a uniform fit of the glass. Once the glue is dry, you can remove the rubber bands and turn on the phone for a full test.
⚠️ Warning: Do not turn the phone on to charge immediately after assembly if you have used liquid glue.Let it dry completely (minimum) 1-2 hours), so that the alcohol vapor does not damage the components, and the glue itself gained strength.
Battery calibration and software settings
After a physical battery change, Android may not display the charge level correctly because the power controller remembers the parameters of the old battery, which requires a calibration procedure to correct, which will help avoid a situation where the phone shows 20% and then abruptly turns off.
There are several calibration methods. The easiest and safest way is to completely discharge the phone before it turns off, then charge it to 100% when it's off, then hold it on for another 1-2 hours after reaching 100%, then turn on the phone and check the indicator.
For deeper calibration, you can use an engineering menu or special applications, but in Xiaomi with a MIUI shell (or HyperOS), it is often enough to simply cycle a full discharge-charge cycle. It is also recommended to reset the battery usage statistics in the settings, if such an option is available, or simply wait for 2-3 cycles of work.
It is also important to update the software to the latest version. Manufacturers often release patches that optimize power consumption for new batches of batteries or correct errors in the algorithms of the power controller. Go to Settings → About Phone → System Update and check for updates.
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Proper battery calibration after replacement extends the life of the new battery and ensures an accurate display of the percentage of charge, which is critical for the device’s operation planning.