Xiaomi Mi Power Bank 2C 20800 mAh
charge-controller
USB-Type-C
This article will help you safely open the case, diagnose malfunctions and replace damaged components if necessary, and we will look at what tools you need, how to avoid short circuits when working with lithium-ion cells, and what to do if the device does not turn on after disassembly. Importantly, if you are not sure about your soldering skills or electronics, you should contact a service center, errors can lead to a battery fire.
Before you start, consider: disassembling Xiaomi Power Bank 20800 mAh will void the warranty (if it is still valid). Also remember that lithium-ion batteries are sensitive to mechanical damage and overheating. If the case is swollen or there is a characteristic smell of burning, do not try to disassemble the device yourself: this is a sign of a critical malfunction that requires professional intervention.
1. Disassembly preparation: safety tools and measures
Xiaomi Mi Power Bank is a power bank 2C You'll need a minimum set of tools, but you won't need some:
- 🔧 Plastic mediators or guitar mediators (2-3 Pc.) - for a careful opening of the body without scratches.
- 🔨 Thin screwdriver with a flat sting (1.5-2 mm) - for slapping latches.
- 🔥 A soldering iron with a thin sting (25-30 W) and solder - if you need to unplough the wires.
- 🧲 Magnetic mat or tray - so as not to lose small details (screws, springs).
- 🔋 Multimeter – to check the voltage on the batteries and controller.
- 🧤 Protective gloves and glasses – Lithium-ion cells can ignite if damaged.
Before you start, completely defuse the power bank, which will reduce the risk of short circuits. Also prepare the workplace: it should be clean, well lit and without foreign objects that could close contacts. If you plan to solder, make sure that there are no flammable materials nearby.
⚠️ Warning: Never use metal tools to open the case unless the batteries are already disconnected from the controller board!Even a small circuit can cause the elements to overheat, bloat or ignite.
If you are disassembling the power bank for battery replacement, purchase similar items with the same parameters in advance:
- Capacity: 2 × 10400 mAh (or 20800 mAh in sum).
- Tension: 3.7V (nominal).
- Type: Li-ion 18650 (size 18×65 mm).
- Manufacturer: preferably Samsung, LG Panasonic (original elements in Xiaomi) LG).
2. Opening of the body: step-by-step instructions with a photo
Xiaomi Mi Power Bank 2C 20800 mAh is made up of two halves, latches and glue, and there are no screws inside, which makes it easier to disassemble, but requires care:
Step 1: Take a plastic pickup and insert it into the gap between the top and bottom of the case, and start at the corner next to the Type-C connector, where the latches are less durable.
Step 2. Carefully drive the mediator along the seam, gradually snapping the mounts. If you feel resistance, don't push harder, you better move to another area. Don't try to open the body in one pass!
Step 3: Once most of the latches are opened, separate the top cover. Be careful: flexible plumes or wires may be glued inside (depending on the revision of the device).
Step 4: If the body does not respond, heat the seam lightly with a hair dryer (temperature not higher than 60).°C) - this will soften the glue. Don't use an open fire!
☑️ Checklist before opening the hull
Inside you'll see:
- 🔋 Two lithium-ion batteries LG INR18650 MJ1 (similar).
- 📱 Printed circuit board with charge/discharge controller (Texas Instruments chip) BQ25895 or similar).
- 🔌 Connectors USB-A and Type-C soldered to the board.
- 📶 Wireless charging antenna (if you have a model with Qi).
⚠️ Warning: If batteries are swollen or show signs of corrosion, do not touch them with your bare hands or try to remove them without protection!
3. Diagnosis of malfunctions: what could have broken?
After opening the case, you need to determine which component has failed, and here are the most common problems and their signs:
| Symptoms. | Probable cause | How to check |
|---|---|---|
| No charge from the grid. | Type-C connector or charge controller damaged | Call the circuit from connector to board with a multimeter (~5V charging-on). |
| It's not giving power to the devices. | Discharge controller or fuse is faulty | Measure the voltage at the exit USB-A (must have 5V). If not, check the battery chain to the connector. |
| It's discharged fast. | Battery degradation or high self-discharge | Measure the voltage at the terminals of the batteries without load. 3.2V — worn-out. |
| Not included (no indication) | Chain break between batteries and board or burnt-out controller | Ring the wires from the batteries to the board, check the voltage at the controller input. |
| Overheats when charging | Short circuit in batteries or controller failure | If the case is hot even without loading, turn off the device immediately! |
To check the batteries, disconnect them from the board (neatly unfurl the wires or remove the connector, if any) and measure the voltage at the terminals with a multimeter:
- 🔋 3.7–4.2V — normality.
- 🔋 3.0–3.7V — discharged, requires charging.
- 🔋 Below. 2.5V — deep discharge, possible irreversible degradation.
- 🔋 0V — break or short circuit within the element.
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If the battery voltage is normal but the power bank is not working, the problem is most likely the controller. Try temporarily connecting the batteries directly to the load (for example, an LED with a resistor) - if they give off current, the charge is to blame.
4. Battery replacement: cell selection and soldering
If the diagnosis shows the batteries are worn out, they can be replaced. - Xiaomi Mi Power Bank 2C 20800 mAh will fit elements of the 18650 format with parameters:
- 🔋 Capacity: 3400-3600 mAh (for two elements, a total of 20800-21600 mAh).
- 🔋 Maximum discharge current: ≥10A (for example, Samsung INR18650-35E or LG INR18650 MJ1).
- 🔋 Protection: elements must be without built-in protection fee (it is already on the main board of the power bank).
How to replace batteries:
- Sell old items off the board by remembering the polarity (+ and −).
- Salt new batteries, observing the same polarity. Use thin solder and do not overheat the cells (soldering should take no more than 2-3 seconds per contact).
- Secure the batteries in their original place (usually they are fixed with double-sided tape or thermal glue).
- Check the multimeter voltage at the exit USB-A — must have 5V.
⚠️ Warning: Never solder batteries connected to the board! Detach them by all means, otherwise you risk burning the controller.
What if the new batteries don’t hold the capacity?
5. Controller and connector repairs
If the problem isn't with the batteries, it's probably the charge/discharge controller or connectors that are at fault.
- 🔌 Oxidation or break of contacts Type-C/USB-A: Clean the connectors with alcohol and check the integrity of the tracks on the board. If the contacts fall off, solder them back.
- 📱 Burnt controller (chip) BQ25895 Or similar: If the board is blackened or there is a characteristic smell of burning, the controller must be replaced. You can buy a new one on AliExpress (see the chip number.
If you are not sure about your chip soldering skills, it is better to order a new fee in the collection (for example, on AliExpress for the request "Xiaomi 20800 mAh". PCB"). Cost: about 500-1000 ₽, What is cheaper than buying a new power bank.
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Before soldering the controller, be sure to remove the old solder from the contacts! Use the braid to remove the solder or solder flux RMA-223.
Shell assembly and testing
After repair, you need to properly assemble the power bank to avoid short circuits and mechanical damage.
Step 1. Make sure all wires are connected to the board and the batteries are securely secured. Check the polarity again!
Step 2. Carefully stow the board and batteries inside the case. Make sure nothing presses on the cells.
Step 3: combine the latches on the body and press until the characteristic click. If the body does not close tightly, check if the wires are disturbing.
Step 4. Connect the power bank to the charger and check:
- 🔋 Charge indication (LEDs should light up).
- 📱 Exit voltage USB-A (5V).
- 🔥 Absence of overheating (the body should be slightly warm, but not hot).
⚠️ Warning: If the power bank doesn't turn on after assembly, don't try to force it to charge (e.g., by applying the voltage directly to the batteries). This could cause an explosion! Disassemble the device again and check all connections.
If everything works, calibrate the controller:
- Completely discharge the power bank (before the display is turned off).
- Charge to 100% and hold on charging for another 1-2 hours.
- Repeat the cycle 2-3 times – this will help the controller to correctly determine the capacity.
7. Frequent mistakes and how to avoid them
When you repair your Xiaomi Power Bank 20800 mAh, many people make the same mistakes, and here are the most common ones and ways to prevent them:
- ⚡ Short circuit when soldering: Always disconnect batteries from the charge before soldering! Use isolated tweezers to hold the elements.
- 🔥 Battery overheating: When soldering, do not keep the soldering iron stinger on the battery contacts for longer than 2-3 seconds.
- 🔧 Damage to the latches of the case: Do not use metal tools to open! Plastic mediators or special devices for disassembling smartphones will be better.
- 📉 Incorrect calibration: After replacing batteries, many forget to perform charging/discharge cycles, which is why the controller shows incorrect capacity.
- 🔋 Use of incompatible batteries: Cells with protection or inadequate capacity can cause a controller to fail or even fire.
If you're in doubt, go to the service center. Lithium-ion battery repairs are no joke: a mistake can cost you money, but also your health.