Xiaomi’s external batteries have been considered the benchmark for reliability in the portable energy segment for many years. However, even the highest-quality lithium polymer or lithium-ion cells lose their capacity over time, which leads to the inability to fully charge a smartphone. Owners often wonder whether it is possible to revive the device or replace it with new “banks” to prolong the life of the gadget.
The process of disassembling Xiaomi Power Bank 20,000 mAh is not a trivial task, as the manufacturer specifically designs the case monolithic to prevent the possibility of accidental opening by the user. This is dictated by safety reasons, because inept handling of batteries can lead to short circuit or even fire.
Before you start taking action, you need to be clear that opening the case automatically voids the warranty obligations of the manufacturer. If your device is less than a year old and it has failed due to the fault of the plant, it is wise to use a service center. In this article, we will discuss the technical side of the process for those who are willing to take responsibility for the result.
⚠️ Warning: Inside the enclosure are energized power supplies. Do not use metal tools without insulation, so as not to accidentally close the contact plate or battery terminals.
Tools and workplace preparation required
The success of the disassembly operation depends on the quality of the preparation, and you need not only physical strength, but also a set of specific tools that will allow you to act on the body without damaging it critically. A standard set of screwdrivers will not be enough here, since the main fasteners are hidden under decorative elements.
To work, you will need the following tools:
- 🛠️ Thin metal blade or medical scalpel for opening latches.
- 🔥 A hair dryer or thermophen for careful heating of adhesive compounds.
- 🧤 Dielectric gloves to protect hands and prevent static discharge.
- 🔦 Powerful flashlight for inspection of internal components in the depth of the body.
Special attention should be paid to the desktop, the surface should be clean, dry and not conduct electric current. It is recommended to cover the table with an antistatic mat or at least a sheet of dense paper so that small cogs and details are not lost. It is also important to ensure good lighting, since there are many small elements inside the case.
Many people forget about isopropyl alcohol or the special liquid B-7000, which may be needed to dissolve the glue. If the body is glued around the perimeter, mechanical action without chemical treatment can lead to breakage of the plastic ears of the mounts. Heating also softens the adhesive, making the process less traumatic for the mounts.
☑️ Preparation for disassembly
Definition of model and type of shell design
Xiaomi’s 20,000 mAh line of external batteries includes many modifications, from the first aluminum versions to new plastic models with support for fast charging Quick Charge and Power Delivery. The design of the case is radically different depending on the generation of the device, which dictates its algorithm of actions.
The main types of construction you may encounter:
- 📦 Aluminum non-shatterable body: Characteristic of early models (Mi Power Bank 1 and 2). end plugs here are often planted on glue and do not have visible screws.
- 🔩 Plastic case with screws: Found in newer versions where fasteners can be hidden under rubber legs or a nameplate.
- 🧩 Internal latch system: The most common option where the two halves of the body are connected by plastic clips around the perimeter.
The first step is always to look closely at the ends and back, look for any holes, recesses or stickers that might be hiding screws, and in some models, screws are hidden under rubber slip pads at the bottom of the device, and if there are no screws, then the case is held exclusively on latches and glue.
How to distinguish the original from a fake body?
It's important to understand that aluminum-body models often use rolling or glue-layered tight fitting, and it's almost impossible to untang a block without a trace, so repairs often involve tricks like carefully drilling the attachment points or using the finest strings to cut the glue.
Technology of accurate opening of the body
The opening process starts with finding the entry point. If the screws are missing, you need to find the joint between the top and bottom cover. The best place to start is with the USB connector, because there's usually a technological gap. Put a thin plastic card or a scalpel blade in there (carefully!) and try to push the halves slightly apart.
Move the instrument along the perimeter, sequentially snapping the locks. You'll hear the characteristic clicks as the plastic tongues come out of the grip. Don't try to open the body completely on one side, it will break the latches. Walk around the circuit, relaxing the tension evenly.
If the body doesn't lend itself, it's probably glued together.
- Heat the ends of the device with a hair dryer to a temperature of 60-70 degrees (do not overheat so as not to damage the batteries).
- Let the device cool a little so that the glue becomes viscous, but not liquid.
- Repeat the procedure with the shoulder blade, gently penetrating deep into the joint.
⚠️ Attention: It is strictly forbidden to use force by jerking.Abrupt movement can cause the plumes connecting the display board to break with the main controller, or damage to the insulation of the batteries.
In some cases, especially in aluminum cases, you have to remove the end plastic plug, which can be held on two small screws under the specification sticker. Carefully unstick the sticker (to then stick a new one or the same one), unscrew the screws and pull the plug on yourself, which will open access to the insides.
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If the screws under the sticker are sour or ripped, use superglue. Apply a drop of glue to the screwdriver sting, apply the screw cap, wait for drying and try to unscrew.
Diagnostics of internal components and replacement of elements
When you successfully remove the lid, you'll see the internal Power Bank device, and you'll see a control board (BMS) that's connected to 18650 cylindrical batteries (old models) or flat lithium-polymer packages (new ones), and the main task is to determine what's gone wrong.
The most common problem is with the batteries themselves, and over time, they fall into a deep discharge, or one of the cells goes into a deep discharge, blocking the entire system, and you can check the state with a multimeter, measuring the voltage on each cell, and it should be in the range of 3.0-4.2 volts.
What to look for in the diagnosis:
- 🔋 Bloating: If the jar is bloated, it must be disposed of immediately.
- 🔌 Contact integrity: Check the soldering sites of the nickel plates. Often, vibration or corrosion causes contact to fall off.
- 💡 Indication: When charging, do LEDs light up? If not, the charge controller may have burned down.
If you need to replace, old cells are soldered or carefully bitten off (polarity!), and new ones are installed in their place. It is important to use elements of the same capacity and preferably from the same manufacturer. Use pure nickel and spot welding to connect, since soldering with a soldering iron heats the battery, which is harmful to it.
Table of compatibility and characteristics of elements
When replacing, it is critical to find the right batteries. Using the wrong batteries can lead to incorrect controller operation or even fire. Below is a table with the main parameters to consider when choosing a replacement for various Xiaomi models.
| Parameter | Description | Normal value. | Critical significance |
|---|---|---|---|
| Type of element | Battery form factor | 18650 (Li-Ion) or Li-Pol | Incompatible dimensions |
| Nominal voltage | The cell's working voltage | 3.7 V V | Below 2.5 V (deep discharge) |
| Capacity | Energy intensity of a single cell | 2500-3500 mAh | Different capacity in assembly |
| Current output | Maximum discharge current | High Drain (High Drain) | Low (for flashlights) |
Note the current rate. External fast-charging batteries (18W, 22.5W and above) require high-current output cells (typically 10A and above) and if you put conventional low-current-rate cells in, they will overheat and degrade quickly when you use high-powered smartphones.
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When assembly, always use elements with the same internal resistance and voltage, pre-charge them to the same level (3.8-4.0V).
Assembly of the device and check of performance
After replacing the items or repairing the board, you need to reassemble the device. Before closing the case, be sure to conduct an initial test. Connect Power Bank to the network and check if the charging indication lights up. Then plug in the load (such as a light bulb or an old phone) and make sure that the discharge is going.
If everything works correctly, you can start assembly. Carefully stow the elements into the seats, avoiding wire bending. The board should sit tight, without backlashes. Connect the halves of the body, starting on one side, and gradually press around the perimeter until the characteristic click of all latches.
Nuances of the final assembly:
- 🧹 Cleanliness: Make sure there are no villi, wire clippings or tools left inside.
- 🔒 Fixation: If the screws have been ripped, use a little heat-glue to fix the lid, but not dead.
- 🌡️ Temperature control: After the first full charge, touch the body. It should not be hot, only slightly warm.
The final step is to calibrate the controller, and to do this, it is recommended to completely discharge the device to zero (before turning off) and then charge it to 100% without interruption, which will help the battery management system (BMS) correctly determine the real capacity of new elements and correctly display the percentages of charge.
⚠️ Warning: If you smell burning, hear hissing, or see smoke when charging, immediately disconnect the device from the mains and take it out into the open.