Why the Redmi Note 8 battery fails and when to change it
Xiaomi Redmi Note Smartphone 8, released 2019 year, equipped with a non-removable battery capacity 4000 mAh (model) BM47). Over time, even the original battery loses its value. 30-40% post-capacity 500-800 If your machine is running out of charge, 3-4 for a period of time with moderate use, switched off 20-30% charging or overheating during charging are sure signs of battery degradation.
The manufacturer claims a battery life of 2-3 years of active use, but in practice this period is reduced due to:
- 🔌 Constant fast charging (especially with cheap adapters)
- 🌡️ Overheating during games or under direct sunlight
- 📴 Deep discharges (below 5%) followed by charging up to 100%
- 🛠️ Mechanical damage (shocks, falls)
Before replacing, check the battery status through an engineering menu (#4636### → Battery information) or an app like AccuBattery. If the Health score is below 70%, a replacement is inevitable. Using a worn-out battery is dangerous: it can swell and damage the screen or motherboard.
What tools and materials will be needed
For a self-replacement, prepare:
| Tool/material | Appointment | Where to buy |
|---|---|---|
| Plastic mediators (2-3 units) | Safe compartment of the back cover | AliExpress, Radio Goods Stores |
| Cross screwdriver PH00 | Screwing of screws | Any hardware store |
| Suction (optional) | Lifting the cover after warming up | Phone repair kits |
| Fryer-dryer | Softening of glue (temperature 60-80 °C) | Construction shops |
| New BM47 battery (original or analogue) | Replacement of an old battery | Xiaomi Official Services, Verified Sellers |
⚠️ Warning: Do not use metal blades - they scratch the body and can close contacts on the board.°C, otherwise damage the display or plumes.
Step-by-step: how to disassemble the Redmi Note 8
Turn off the phone before you start and remove it. SIM-Work on a clean, illuminated surface, so you'd better cover the table with a soft cloth.
- Warm up the back cover. Dryer heat the edges of the body evenly around the perimeter for 2-3 minutes. Keep the hair dryer at a distance of 5-7 cm so as not to overheat the plastic. The glue under the lid becomes elastic.
- Separate cover. Insert the plastic mediator into the gap between the cover and the housing (start at the bottom edge where the charging connector is). Carefully drive the mediator along the edge, separating the latches. If the cover does not respond, warm up for another 1 minute. 💡If the cover is raised, but not removed - check whether there are undetached latches in the area of the volume buttons or the camera.
- Spinning screws. Under the lid, you'll see 12 screws of varying lengths. Unscrew them all and spread them out in order (preferably take a picture of the location). The screws at the antenna contacts are shorter than the others!
- Disconnect the plumes. Carefully tuck the black battery, display and camera plume connectors (use a plastic blade). Don't pull the wires -- just the connectors!
Phone turned off and removed. SIM-map|The back cover is warmed up by a hairdryer.|Separated body with plastic mediator|All screws twisted and saved|Battery and display plumes disconnected-->
How to safely remove an old battery
The battery in the Redmi Note 8 is glued to the body with double-sided tape. Don't try to rip it out - it could damage the board or the battery itself (fire risk!).
- Put a battery in. Put a plastic blade under the battery on the connector side (there are no circuit board components). Try to lift the edge by 1-2 mm.
- Apply isopropyl alcohol. Put 70-90% alcohol under the battery at the glue points. It dissolves the glue in 5-10 minutes. Repeat the procedure 2-3 times.
- Remove the battery. After softening the glue, gently pull the traction tape (if any) or slap the battery with a mediator. Don't rot it or use metal tools!
⚠️ Warning: If the battery is swelling (the case cover is raised), do not puncture it! This may cause fire.
Once removed, inspect the contacts on the board, clean them with a dry brush or compressed air, and if there are traces of oxidation (green coating), remove them with a blower or alcohol.
Installation of a new battery and assembly of the phone
Before installing the new BM47 battery, check:
- 🔋 Presence of protective film on contacts (do not remove it before installation!)
- 📏 Compatibility of size and shape to the original
- 🔌 Integrity of plume and connector
Installation procedure:
- Stick the new battery onto double-sided tape (comes with it) and don't use superglue or heat-glue!
- Connect the battery plume to the circuit board connector, and it should snap with a click.
- Put the display and camera plumes in their seats, make sure they're not covered.
- Turn all the screws in reverse order. Start with the long ones (at the board), then the short ones (at the antennas).
- Press the back cover until the snap of the latches. Warm up the edges with a hairdryer (60°C) for better glue fixation.
💡
After assembly, do not turn on the phone immediately - wait 10-15 minutes for the glue to grab and all contacts to sit down.
Calibration of the new battery and check of performance
After replacing the battery, calibrate to ensure that the system correctly determines the level of charge:
- Charge your phone to 100% original adapter (you’d better use Xiaomi 18W).
- Turn off the charging and use the device until it is automatically turned off (not to 0%!).
- Repeat the charging/discharge cycle 2-3 times, and this synchronizes the battery controller with the new capacity.
Check the operability:
- 📱 The phone is turned on and off without hanging.
- 🔋 Charging is stable (no percentage jumps)
- 🌡️ The body does not overheat during charging or loading
- 🎮 Performance in games/benchmarks has not fallen
⚠️ Note: If the phone does not turn on after replacement, check: Density of the battery plume to the connector Integrity of contacts on the board (is there oxidation) Correctness of connecting the remaining plumes (display, power button) If you suspect a short circuit, do not connect the charging - contact the service.
Frequent Mistakes and How to Avoid Them
Even with a careful replacement, beginners make mistakes that lead to breakdowns.
| Mistake. | Effects of consequences | How to avoid |
|---|---|---|
| Use of metal tools | Scratches on the body, closing contacts | Only work with plastic mediators |
| Hair dryer warms above 90°C | Melting plastic, detachment of plumes | Control the temperature with a thermometer |
| Tangled screws | Damage to boards or antennas | Place the screws in order or take pictures |
| Strong battery bending | Rip of the shell, risk of fire | Remove the battery slowly, without jerking |
Another common problem is the fast discharge of the new battery, which is because of:
- 🛠️ Low-quality battery (buy only from trusted sellers)
- 📱 Background processes (check in Settings) → Battery)
- 🔌 Non-original charger