Many owners of the popular fitness tracker face the need for internal intervention in the device, most often due to battery failure or damage to the display.
But you have to understand that the Xiaomi Mi Band 4 is a sealed device that is not designed to be easily accessible inside. The bracelet design involves a tight fit of the module in the strap, and the body itself is glued or soldered, and any violation of the integrity of the body automatically deprives you of an official warranty.
In this guide, we will look at all the steps of dismantling, the tools you need, and the common mistakes you should avoid. If you are determined to act, carefully study each step before you start work. Accuracy and accuracy are your main allies in the process.
Preparation of the workplace and tools
Before you start physically impacting the device, you need to have the right workspace, you need a desk with good lighting, preferably a daylight, or a high-powered neutral-spectrum desk lamp, and you can lose small parts, so the surface should be clean and flat.
To successfully replace the battery or screen in the Mi Band 4, you'll need a specific set of tools. A standard screwdriver won't be enough here. The main difficulty lies in the miniature screws and the dense assembly of the module.
- 🛠️ Thin metal spatula or scalpel to open the body.
- 🔥 Hair dryer (construction or household) for softening glue.
- 🔋 New battery (model) HJ-125428 analogue).
It is also recommended to prepare tweezers with thin curved ends and a plastic card or mediator. Metal tools can damage the lithium polymer battery, which is fraught with fire, so act with extreme caution.
⚠️ Warning: Be sure to discharge the battery to a minimum before work begins.Puncture or damage to the charged battery can lead to instant ignition of the electrolyte.
Don't neglect safety. Work in a well-ventilated environment, because when the glue is heated, it can release toxic substances. Organize all tools so that they are at hand, but do not interfere with movement.
Removing the tracker from the strap
The first step in any disassembly is to remove the main module from the silicone strap. Unlike previous versions, the Xiaomi Mi Band 4 has rounded edges, which makes the process a little more complicated. You need to push the tracker out.
So you can hold the device in your hand so that the screen is pointing away from you, and on the back of the capsule, in the recess, there's a special protrusion, and that's where you press your thumb, while you pull the module out with your other hand.
- 👆 Press on the inside of the strap at the place of attachment of the capsule.
- 🔄 With swinging movements, remove the tracker from the silicone frame.
- 🧤 Use gloves if the strap is new and slippery, for better grip.
If the module is too tight, you can slightly warm the silicone with a hair dryer, but do not overdo it so as not to deform the material. After removal, inspect the body for visible damage or autopsy marks.
Now you have the main unit with the screen and the battery, and that's what we're going to do with the next manipulation, and you're going to put the strap in a safe place so you don't lose it.
☑️ Pre-mortem checks
Opening of the body and removal of the back cover
The hardest part of the process is to separate the back cover from the main body, and the factory assembly involves using a powerful adhesive and not having screws at this point, and you need to be patient and enduring.
Turn on the dryer at medium power and start warming the perimeter of the back cover. Keep the heat source 3-5 cm away from the device, constantly moving it so as not to overheat the display or battery. The heating process takes about 2-3 minutes.
Once the body is warm to the touch, carefully insert a thin metal blade or blade into the junction between the front and rear. Act slowly as you move around in a circle.
| Tool. | Risk of damage | Efficiency |
|---|---|---|
| scalpel | High (you can cut the plume) | Tall. |
| Metal spatula | Medium. | Medium |
| Plastic card | Low. | Low (may not break the glue) |
Don't try to open the lid with one jerk. The glue should soften evenly. If you feel strong resistance, stop pulling and warm up the area again.
⚠️ Attention: Under the back cover is the battery immediately. Do not enter the tools deep so as not to damage the battery shell and cause a short circuit.
Once the lid is successfully detached, you'll see the internal layout of the device, and you'll see the battery glued to the case and the main board.
Dismantling of battery and plume
Inside the Mi Band 4, the battery is almost 70 percent volume, it's fixed with double-sided tape, it's going to take a neat retrieval, and then you're going to shovel it with a blade from the edge opposite to the contacts.
The display plume is connected to the board via a miniature connector, which can be further fixed with glue or plastic lock, and use tweezers to gently lift the lock, if any, and disconnect the plume.
- 🔋 Unplug the old battery by putting it on a spatula.
- 🔌 Disconnect the screen plume from the motherboard.
- 🧹 Clean the landing site of the remnants of old glue with alcohol.
When working with the contact group, be extremely careful. Microscopic contacts are easy to damage or bend. If the connector of the plume is damaged, replacing the battery will not help - the device will not turn on.
Recycle old batteries properly, don't throw them into household waste. Lithium polymer cells require special recycling.
Where can I find the rations?
Installation of a new battery and assembly
Once the adhesive residue has been cleaned, you can start installing new components, the new battery must have the same dimensions as the original battery, otherwise the lid will not fall into place.
Secure the new battery to a two-way tape. Make sure the wires are not pressed or stretched. Connect the display plume to the click, controlling the force.
Now you need to seal the case, and use a special glue B-7000 or T-7000, which is often used in smartphone repair.
⚠️ Warning: Do not use superglue (cyanacrylate) which becomes too brittle when drying and can damage the plastic elements of the case when disassembled again.
Apply a thin layer of glue around the perimeter of the back cover and press it tightly against the body. Lock the device with rubber rings or a load for 1-2 hours until completely dry.
Once the glue is dry, wipe the body of the glue surplus. Put the module back in the strap. The device is ready for first launch.
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Use B-7000 glue for sealing – it remains elastic after drying, which retains moisture protection and facilitates future repairs.
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High-quality sealing is the guarantee that the tracker will survive the ingress of water or sweat during training.
Typical errors and their consequences
Even experienced craftsmen make mistakes with small electronics. In the case of the Xiaomi Mi Band 4, the cost of error is high, as spare parts cost almost as much as a new device.
One of the most common problems is that the plume is damaged when it is opened, and the thin tracks break instantly, and the recovery requires a microscope and a soldering station, and users often forget to check the voltage of the new battery before installing it.
- 💥 Overheating of the body with a hairdryer leads to swelling of the battery or detachment of the screen.
- 🔪 The use of too sharp tools is fraught with cutting current tracks.
- 💧 Lack of sealing after assembly will deprive the bracelet of protection from moisture.
Another mistake is the wrong build sequence, so if you stick the lid first and forget to plug the plume in, you'll have to start over, risking damage to the components.
Take your time. It's better to take 40 minutes to disassemble than 5 minutes to completely disable the device.
What if the screen does not show the image after assembly?
Checking of operability and leakproofness
After assembly, you need to check if the device is working correctly. Connect the tracker to the charger. The charging indicator should light up, and the appropriate animation will appear on the screen.
Sync the bracelet with your smartphone through the Zepp Life app (formerly Mi Fit). Check the pulse sensor, pedometer and vibration. If all functions work, you can consider the repair a success.
When it comes to water protection, it is almost impossible to fully restore the factory level of IP68 at home. The B-7000 glue provides good protection against splashes and sweat, but swimming in the pool or diving with such a device is no longer recommended.
Run a vibration and touchscreen response test across the screen area, and if there are dead zones, the plume may be unevenly pressed or damaged.
| Parameter | Norma. | Deviation |
|---|---|---|
| Charging time. | ~1.5 hours | More than 3 hours. |
| Work at standby | 20 days | Less than 5 days |
| Touchscreen response | Instant. | Delay or omission |
If the device has passed all the tests, congratulations on the successful repair, you not only saved money, but also gained valuable experience in disassembling modern electronics.