How to remove the battery from Xiaomi Mi Band 4: disassembly, tools and warnings

Why do you need to take the battery off the Mi Band 4?

The 2019 Xiaomi Mi Band 4 fitness bracelet is still popular with users due to its combination of functionality and affordable price. However, over time, even reliable devices fail — and most often battery problems. Typical symptoms are that the device does not hold a charge, suddenly turns off at 20-30% charge or completely stops turning on, in which case a replacement battery can restore the bracelet to a second life.

But before you start disassembling, you need to assess the risks. The Mi Band 4 is not designed to be self-repaired: the body is glued together, the battery is soldered to the board. Disassembly errors can lead to damage to the display, plumes break, or even a short circuit. This guide will help minimize the risks, but remember: the warranty on the device is canceled whenever the case is opened.

If you're not sure about your skills, you should go to a service center, but for those who are willing to take risks, we'll go through the process in detail, from the necessary tools to step-by-step disassembly.

What tools will be needed to remove the battery

To carefully extract the battery from the Mi Band 4, you will need a specialized set of tools, without which you can damage the board or the case.

• 🔧 Plastic mediators or shoulder blades (2-3 (a) - for the separation of the glued parts of the body without scratches.
• 🔥 Hair dryer construction or thermo-air station - for heating glue (temperature) 60-80°C).
• 🛠️ Tweezers with thin ends - for working with small details and plumes.
• ⚡ soldering iron with a thin sting (0.5-1 mm) and solder - if the battery is soldered to the board.
• 🧴 Isopropyl alcohol (90%+) — clean up.
• 📏 Microscope or magnifier with illumination (optional) - to control soldering works.

Also, prepare an antistatic mat and grounded bracelet (on the wrist) to avoid static discharge that can damage electronic components. If you plan to replace the battery, buy an original or high-quality analog one (135 mAh, 3.85V voltage) in advance. Avoid cheap fakes - they may swell or not fit the size.

⚠️ Warning: Don't use metal tools to detach the body! They can close contacts on the board or scratch the screen. Plastic mediators are safer.

Read more about How to Avoid Damage to Mi Band 4

Before you start dismantling, follow a few critical steps:

1. Deplete the bracelet completely. The battery is more dangerous when it's soldering. Wait until the device turns off by itself.
2. Take the strap off. Disconnect the bracelet capsule from the silicone strap by pressing the lock on the back.
3. Clean the case. Wipe the device with an alcohol napkin to remove fat and dirt - these can interfere with bonding after repair.
4. Prepare your workspace. Use a clean desk with good lighting. Put the tools in order of use.

If you plan to solder, work out on an unnecessary board beforehand – the battery contacts on the Mi Band 4 are extremely small, and it is also recommended to take photos of each stage of disassembly (especially the location of the plumes) to facilitate reverse assembly.

Step-by-step: how to disassemble the body of the Mi Band 4

The body of the bracelet is glued around the perimeter, so the main task is to carefully separate it without damaging the internal components.

1. Heat the body. Use the dryer at minimum power (60-70 ° C) and evenly warm the edges of the capsule for 2-3 minutes. The glue will become softer and the risk of damage will be reduced.
2. Separate parts: Insert a plastic mediator into the gap between the front and back panels (start at the button side). Carefully guide the instrument around the perimeter, gradually increasing the gap.
3. Remove the back cover. After the glue seam is separated, remove the back panel. Be careful, there's a vibrator attached to it that can come off.
4. Disconnect the display plume. Under the lid, you'll see a flexible plume connecting the display to the board. Carefully tweez it (don't pull the wires!).

Now you're going to have a soldered board, and don't rush it off, you're going to learn the mount first. In the Mi Band 4, you can have a battery that's:

• Sticked to the payment with double-sided tape.
• It is soldered with two contacts (+ and -).
• It's a glue-sweetened combination.

How to safely disconnect the battery: soldering vs mechanical removal

How you remove the battery depends on how you attach it.

1. Bilateral scotch battery

If the battery is just glued, you can gently tuck it in with a plastic blade. Start at the edge, gradually separating it from the board. Don't put too much effort into it, there may be delicate components under the battery. Once removed, clean the board of glue residues with isopropyl alcohol.

2. Battery soldered to board

You'll need a soldering iron.

1. Put a braid on the contacts of the battery to remove solder and warm up with a soldering iron (temperature 300-350 ° C).
2. After melting the solder carefully remove the slab along with solder.
3. Repeat the procedure for the second contact.
4. Tweez the battery and separate it from the board.

⚠️ Warning: Do not overheat the board! Prolonged exposure to high heat (more than 5 seconds per contact) can damage the chips. Use a power-adjusted soldering iron.

If you plan to install a new battery, pre-check its voltage multimeter. it should be in the range of 3.7-3.85V. Also check the contacts on the board - if necessary, clean them with alcohol.

💡

If you solder the contacts of the new battery using flux on a water-based basis, it less oxidizes the board. After work, be sure to remove the residues with alcohol.

Installation of a new battery and assembly of the bracelet

Once you've successfully removed your old battery, you can start installing a new battery, and the process of reassembling it is just as important, because errors can cause the device to fail.

1. Battery attachment

• If the battery is on tape: glue it to the same place, making sure that the contacts match the areas on the board.
• If you need soldering: Put some flux on the contacts. Put the battery on and tape it. solder first - (minus), then + (plus).

2.Pre-assembly check

Connect the bracelet to charging (without closing the case!) and make sure:

• 🔋 The charging indicator caught fire.
• 📱 The device is defined in the Mi Fit application.
• 🌡️ The temperature of the board does not rise (check with your hand after 5 minutes).

Assembly of the hull

Carefully connect the front and back of the body, making sure that:

• The display plume is tightly connected.
• The vibromotor is in its nest.
• The button is not pressed (check its performance).

Use 3M double-sided tape or B-7000 glue to bond, apply it with a thin layer around the perimeter and tightly compress the parts of the case for 10-15 minutes.

💡

After the battery is replaced, the first charge cycle should be full (up to 100%) and this will help calibrate the power controller.

Frequent Mistakes and How to Avoid Them

Even experienced craftsmen sometimes make mistakes when repairing the Mi Band 4, and here are the most common problems and ways to prevent them:

• 🔥 Use a soldering iron with a thin sting and do not hold it in one place for longer than 3-5 seconds.
• 💥 Short circuit. Before soldering, check with a multimeter that there is no residual voltage on the board. Also avoid tweezing adjacent contacts.
• 📵 Display failure after assembly, which most often means that the plume is not fully inserted into the connector.
• 🔋 Rapid discharge of the new battery, caused by poor battery quality or incorrect calibration. Perform 2-3 full charge/discharge cycles.