Xiaomi's external batteries are well-deservedly among the most reliable on the market, but even they have their own lifespan. Over time, the capacity of lithium-ion cells drops, and the device stops holding the charge or the power controller fails. At this point, many users are thinking about self-repair, since buying a new battery is often cheaper than buying a new Power Bank. However, the process of opening the case involves certain risks and requires care to avoid damaging fragile components.
Before you start disassembling, you need to be aware that you are interfering with a high-current short circuit. Breaking the tightness of the case or damaging the insulation of the wires can lead to fire or explosion of the battery. Unlike smartphones, where batteries are often glued, in power banks, the 18650 can be attached in different ways, and finding hidden screws is only part of the task. This article will help you safely open the device, replacing old cells with new ones, while maintaining the performance of the controller.
It's worth noting that most Mi Power Bank models have a monolithic aluminum body that doesn't offer easy access inside. This is done not only for aesthetics, but also to protect against mechanical damage and provide better heat sink. If your device is still warranty, any autopsy marks, such as scratches on the edges or tearing seals, will lead to a denial of service. So weigh the pros and cons before you pick up the tools.
Tools and workplace preparation required
To successfully and safely disassemble an external battery, you will need a minimal but specific set of tools. A standard household kit may not be enough, since the screws in Xiaomi equipment often have specific hats. First of all, you will need a set of precision screwdrivers, including cross bits of the size of the PH000 and PH00, and possibly a slate screwdriver for tweaking the cells.
Special attention should be paid to tools for opening the body without damage. Aluminum cases Pro or 2 are very sensitive to scratches. Use plastic blades (spoogers) or mediators to crack plugs. Metal tools such as a knife or a stiletto, it is better to postpone, because one awkward movement can damage the insulation of batteries, which is categorically unacceptable.
Also, make sure that the workplace is well lit and does not conduct electricity. It's advisable to use an antistatic mat or just a clean dry surface. Don't forget to use tweezers with curved ends, which will help you extract small screws and fix the wires when soldering, if you replace the elements by soldering.
- 🛠️ A set of precision screwdrivers (mandatory presence of bits) PH000/PH00 Torx T5/T6).
- 📏 Plastic blade or mediator for opening the body without scratches.
- 🔥 A soldering iron with a thin sting and solder (for models with welded contacts).
- 🧤 Dielectric gloves and safety glasses for personal safety.
☑️ Preparation for the disassembly of Power Bank
Design features and search for hidden screws
Xiaomi's external battery design varies depending on model and year of release. The classic Mi Power Bank 1/2/Pro series aluminum "banks" often lack visible screws on the outside. The fasteners can be hidden under decorative plugs, rubber legs, or even under a layer of glue. In newer plastic models, the screws can be placed under the logo or in the indentations of USB ports.
The first step is always to take a close visual look at all the facets of the device. Run your finger over the surface, sometimes the plugs are slightly protruding or have a barely noticeable seam. If you find a rubber pad on the bottom, gently tuck the corner of the pad with a spatula. It often hides two or four screws holding the inner board. In some cases, you need to access the screws to remove the end plastic cap where the connectors are located.
It's important to understand the difference between a collapsible and a non-collapsible body. If you unscrew all the visible screws, don't use force. Perhaps the parts of the body are connected by tight latches around the perimeter or special glue, in which case you need to warm up with a hairdryer (carefully so that you don't melt the plastic inside) or use a thin blade to pass through the junction.
⚠️ Note: In some models, the screws can be closed with warranty stickers, and if you damage them, you automatically lose the right to free repairs at authorized centers.
When you're working with aluminum cases, remember that they act as a radiator. The internal components are not randomly planted tightly, they provide heat removal from the charge-discharge controller. When you build them, it's important to restore the density of the fit, perhaps using heat pads if the old ones are broken.
The process of opening popular Xiaomi models
Consider the most common models. For the classic Mi Power Bank 2 (10,000 mAh), the process starts with removing the end plugs. Carefully tuck in a plastic insert with USB and Type-C ports. Underneath it, you find screws. Unscrew them, you can pull the internal assembly from an aluminum pencil. Be careful: the wires connecting the control board to the batteries can be short.
The Quick Charge and Power Delivery Pro series models are more complex in design, often with two-way control boards and 18650 elements (or lithium-polymer packages in 3 Pro versions) packed tightly. In such devices, the screws can be under the shrinkage layer on the batteries themselves or hidden in the depths of the housing. It is especially important not to damage the insulation, since the voltage in the assembly can reach 16.8 volts (4S configuration).
If you're faced with a monolithic body without screws (found in older or budget versions), it's probably assembled on the latches, in which case you need to insert a thin plastic card into the junction between the halves of the body and, as you move along the perimeter, snap the locks. The movements should be progressive, without jerks. The click you hear means that the latch is free.
What to do if the body is glued together?
- 🔍 Carefully examine the ends of the device - there are most often hidden screws.
- 👐 Do not compress the body strongly at opening, so as not to push the batteries.
- 📸 Take a picture of the location of the wires before disconnecting – this will help with the assembly.
Replacement of power and work with the controller
After a successful opening, you'll see a bunch of 18650 batteries (less commonly 21700 or Li-Pol) that fail one or more cells, and the Battery Management System (BMS) will block the device if it detects a fault in the circuit, and you can't just replace the battery with a new one as is, you have to consider the type of connection.
In most cases, the cells are connected by nickel tape through spot welding. It is highly undesirable to solder batteries with a conventional soldering iron: prolonged heating destroys the internal structure of the electrolyte and can lead to bloating or loss of capacity. If you do not have point welding equipment, it is better to purchase ready-made assemblies (pack) with already welded contacts or use the services of a master.
If you're confident in your soldering skills, use a powerful soldering iron, actively flush the contact area, and act as quickly as possible to avoid heating the battery case. Be sure to observe polarity! By confusing the plus and minus when you connect a new build to the controller board, you will instantly disable electronics. Xiaomi controllers are sensitive to flip.
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Buy batteries with protection only or make sure that a protection charge (PCB) is installed on each cell or on a shared assembly.Using unprotected cells without control is dangerous.
When installing new cells, it is important that their voltage is leveled. If you put 4 cells in series, their voltage should be the same (for example, at 3.7V). Unbalanced will cause one battery to recharge and the other not to recharge, which will quickly kill the new build.
Compatibility table and element parameters
When choosing a replacement, it is important to focus not only on physical size but also on current output. Powerbanks with support for fast charging require batteries with high discharge current. Below is a table with indicative parameters for popular models.
| Model of Power Bank | Type of element | Number (s) | Recommended current output |
|---|---|---|---|
| Mi Power Bank 2 10000 | 18650 Li-Ion | 2 pcs | 5A |
| Mi Power Bank Pro 10000 | 18650 Li-Ion | 2 pcs | up to 10A (high current) |
| Mi Power Bank 3 10000/18000 | 18650 / 21700 | 3-4 pcs | up to 15A (for QC/PD) |
| Mi Power Bank 3 30000 | 18650 Li-Ion | 6-8 pcs | 5-8A |
Note that using low-current-return cells (such as conventional office batteries) in high-power banks will cause them to heat up and degrade rapidly.
Assembly of the device and check of performance
Once the components are replaced, the assembly stage begins. First, check the voltage at the output of the controller board with a multimeter without closing the case. Connect the load (for example, a lamp or a phone) and make sure that the current is running and the indication is working correctly. If everything is functioning, you can start installing the case.
Lay the wires so that they do not clamped or touch the sharp edges of aluminum. If necessary, insulate the folding sites with additional shrinkage. Screw the screws evenly, without undue effort, so as not to break the thread in the aluminum case. Close the decorative plugs.
The final test should include a full charge and discharge cycle. Leave the device to charge for a few hours and monitor the temperature of the case. Light heating is acceptable, but if the case gets hot, immediately stop using - this is a sign of an assembly error or a controller malfunction.
⚠️ Warning: Never leave the charging or disassembly process unattended. Lithium batteries can catch fire if used improperly. Have a sand tank or a class D fire extinguisher (for metals) on hand, although for household needs it is enough to be ready to quickly disconnect the device from the network.
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The main success of the repair is not only the replacement of the battery, but also the quality isolation of all connections and polarity when connected to the controller board.