How to safely get a battery from Xiaomi Redmi 9: disassembly of the case and dismantling the battery

Removing the battery from the Xiaomi Redmi 9 is a challenge faced when replacing the battery, repairing after a fall or getting moisture. Unlike older models with removable covers, here the body is glued together and the battery is fixed with double-sided tape. Wrong actions can lead to damage to the plumes, battery rupture or even fire. This article will help you understand how to extract the battery without risks, what tools you will need and what to pay attention to.

The Redmi 9 (codenamed lancelot) is equipped with a non-removable battery capacity of 5020 mAh, which is soldered to the motherboard via a BMS connector. The manufacturer does not provide a custom replacement, but with the right skills and tools, the procedure is possible at home. Importantly, in 90% of cases, battery damage during dismantling occurs due to the use of improper mediators or excessive heating.

Preparation for disassembly: tools and security measures

Before you start, make sure you have everything you need, and not having at least one tool can make it difficult or dangerous.

• 🔧 Plastic mediators (2-3 (a) - for separation of the body without scratches.
• 🔥 Dryer or thermo-air station - for softening the glue (temperature 60-80)°C).
• 📱 Suction - helps to lift the back cover after heating.
• ⚡ Insulated screwdriver (cross, 1.5 mm) - for screws under the lid.
• 🧴 Isopropyl alcohol (90%+) — glue-residue.
• 🛠️ Tweezers – to work with small details.

Do not use metal blades or knives, which will damage the body and can puncture the battery, and avoid overheating: temperatures above 90°C deform plastic and increase the risk of thermal damage to the battery.

⚠️ Warning: If the battery is swollen or shows signs of corrosion, do not heat it - this can lead to fire.

Step 1: Removing the back cover

The first step is to separate the back from the body, and on Redmi 9, it's glued around the perimeter, so you need to heat it evenly.

1. Turn off the phone and remove the tray for SIM-map.
2. Warm up the edge of the body with a hair dryer (for 20-30 seconds on each side) at a distance of 5-7 cm.
3. Push to the bottom of the lid (near the USB-C connector) and pull up.
4. Insert a plastic mediator into the resulting gap and carefully lead it along the body.

If the lid doesn't respond, repeat the heat. Don't put too much effort into it, it can break latches or damage antenna modules under the lid. On Redmi 9, the flexible camera plumes and fingerprint scanner that attach to the motherboard are particularly vulnerable.

Is the phone off-charging? |

Is the tray removed? SIM-map|

Is the heating temperature sufficient (not above 80°C)|

Is there a backup mediator in case of breakdown?-->

Step 2: Disconnect the battery from the motherboard

When the lid is removed, the first thing you need to do is disconnect the battery to avoid short circuits. On Redmi 9, the BMS connector is located at the top of the board and is closed with a black insulation tape.

1. Remove the insulation tape from the battery connector (it is usually weakly glued).
2. Carefully dent the connector with a plastic mediator and disconnect it from the board.
3. Check with a multimeter that there is no voltage on the contacts of the battery (should be 0 V).

If the connector doesn't detach, don't pull it by force, it can tear the paths on the board. Try wiggling the mediator slightly left-right. On Redmi 9, the connector often gets cranky due to oxidation, especially if the phone was in wet conditions.

⚠️ Warning: If the phone still responds to the power button after the battery is turned off (e.g., vibrates), it means the battery is not completely disconnected.

Step 3: Dismantling the battery from the adhesive base

The battery in Redmi 9 is locked in high-strength double-sided tape, and it takes a combination of heat and mechanical action to remove it.

1. Plug a capron thread on the battery (you can use a guitar string or a fishing line 0.2-0.3 mm thick) along the long side.
2. Heat the body with a hair dryer (temperature 70–80°C) for 1-2 minutes to soften the glue.
3. Carefully pull the ends of the thread, "saw" it with a glue layer. Move from one edge to the other.
4. If the battery fails, repeat the heating and add isopropyl alcohol under the edge of the battery (it dissolves the glue).

Don’t use metal objects to tamper with the battery, it can puncture the battery shell. On the Redmi 9, it is especially dangerous to damage the area near the charging controller (located under the battery), as this can disable the entire board.

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If the battery is swelling but not yet deformed, put the phone in a sealed bag and take it to the service for 24 hours.

Step 4: Check the battery and prepare for replacement

After removal, examine the battery for:

• 🔋 Bloating – even a slight deformity indicates a malfunction.
• 💧 Corrosion traces – green or white plaque on contacts.
• 🔥 Darkening – a sign of overheating or internal short circuit.
• 📉 Capacity – if the battery is discharged in 2-3 hours, it is time to change it.

To test the capacity, you can use testers like the ZKE EBC-A20 or applications like AccuBattery (before dismantling). Normal wear for the Redmi 9 after 2 years of operation is 20-30% of the original capacity. If the loss exceeds 50%, replacement is required.

Before installing a new battery, clean the seat of glue residue with alcohol and check the integrity of the thermal sensor (a thin wire running from battery to board). On Redmi 9, it often breaks off when sloppy dismantled, leading to charging errors.

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Never use a battery with visible damage, even if it is "working," and the risk of a sudden fire or explosion increases by a factor of 10.

Frequent Mistakes and How to Avoid Them

Even experienced craftsmen sometimes make mistakes when working with Redmi 9.

• 🔌 Forget to turn off the battery before dismantling → short-circuit.
• 🔥 Overheating the hull → Deformation of plastic, damage to screen or cameras.
• 🛠️ They use metal tools. → scratches, battery punctures, plume cliffs.
• 📱 Do not check the new battery before installation → Fault or incompatibility with the charging controller.

To minimize the risks, follow the three-check rule:

1. Check the power outage (multimeter).
2. Check the integrity of the plumes after removing the lid.
3. Check the compatibility of the new battery (capacity, connector, presence of a thermal sensor).

On the Redmi 9, it is especially important to use a battery with the original BMS connector. Cheap analogues can misrepresent the charge level or cause overheating.

Installation of a new battery and assembly of the phone

The installation process is reversed, but there are a few nuances:

1. Apply a new double-sided tape to the battery (e.g. 3M 9448A) or use a B-7000 glue.
2. Connect the BMS connector to the board and fix it with insulation tape.
3. Make sure the thermometer is not compressed and connected correctly.
4. Press the battery evenly, avoiding distortions.
5. Before installing the cover, check the operability (turn on the phone without the cover).

After assembly, perform battery calibration:

1. Charge your phone to 100% and hold on charging 1-2 hours.
2. Discharge until automatic shutdown.
3. Repeat the cycle 2-3 times.

This will help the controller correctly determine the capacity of the new battery. On Redmi 9, after the battery is replaced, you may need to reset the BMS settings through the engineering menu (code ##4636# → Battery information → Reset).

FAQ: Answers to Frequent Questions