Xiaomi Power Bank 20000 mAh: tools, schemes and secrets of repair

Why to disassemble Xiaomi Power Bank and when it is justified

Xiaomi Mi Power Bank 20000 mAh is one of the most popular external batteries on the market due to its combination of capacity, compactness and reliability. However, even such a device can eventually fail: batteries inflate, stop working. USB-port or power button breaks. Powerbank disassembly is required in several cases:

First, to replace the battery cells that lose capacity after 300 to 500 charging cycles; second, to repair electronics — to restore contacts, solder connectors or replace the charge controller; third, disassembly may be necessary for modding: installing more powerful elements or adding wireless charging. But before you start screwdriver, assess the risks: improper disassembly can lead to short circuit, fire or complete loss of the device.

If your Xiaomi Power Bank 20000 mAh stops holding the charge, does not turn on or warms up when charging, this is a direct signal for diagnosis. However, not all breakdowns require disassembly: sometimes the problem lies in the cable, charger or software failure of the controller. Before opening the case, check the device with another cable and power supply, and try to reset the settings (if the model supports this function).

What tools will be needed to disassemble

For a neat disassembly of Xiaomi Mi Power Bank 20000 mAh, you will need a minimum set of tools, but some of them should be of high quality.

• 🔧 Plastic blade or mediator - to disconnect the latches of the body without scratches.
• ⚒️ Cross screwdriver (PH0 or PH00) — Most of the screws in Xiaomi power banks have a small cross slit.
• 🔥 A soldering iron with a thin sting (20-30 W) – if you plan to unplug batteries or repair the board.
• 🧲 Magnetic mat or tray – so as not to lose small screws and details.
• 🔍 loope USB-microscope - to inspect the board for microcracks or burnt-out elements.
• 🧤 Gloves and safety glasses – batteries can contain caustic electrolytes.
• 📏 Plastic tweezers - for careful extraction of plumes and connectors.

If you are planning to replace batteries, prepare:

• 🔋 New Li-ion cells 18650 (for example, Samsung INR18650-35E or LG MJ1) capacityless 3400–3500 mAh.
• 🔌 Nickel tape or wires for connecting cells.
• 📉 Multimeter - to check the voltage on the cells (should be 3.6-4.2 V).
• 🧴 Thermoclee or double-sided tape - for fixing batteries inside the housing.

⚠️ Warning: Never use metal tools to detach the body - they can close the contacts of the battery. Even a small spark can cause the lithium-ion cells to ignite.

Disconnect the device from charging and discharge to 0%

Prepare a work place on a non-combustible surface

Wear protective gloves and glasses

Check the tools for no damage.

Take a photo of the body from all sides for reverse assembly-->

Step-by-step instructions: how to disassemble the body

The Xiaomi Mi Power Bank 20000 mAh has two plastic halves held together by latches and screws, and it requires careful disassembly, because plastic is fragile and latches are easy to break.

1. Step 1. Plug off the stickers and find the screws on the bottom of the case (from the side). USB-There are two stickers in the ports, one with technical information, one with decorative information, and carefully put a plastic blade under them, and there are 4 screws underneath them (some versions have 5.
2. Step 2. Disconnect the latches. Insert the plastic blade into the gap between the top and bottom of the body (better start from the side opposite the body). USB-Carefully drive the blade along the seam, disengaging the latches. Be careful - if you exert too much force, plastic can crack.
3. Step 3. Remove the top cover. Once all the latches are disconnected, lift the top of the housing.Inside, you'll see the battery pack (two cells 18650), the control board and the connecting wires. Don't pull the lid sharply - it can be connected to the power button with a plume.
4. Step 4: Disconnect the button plume (if any) in models with a charge indicator, the power button is connected to the board through a thin plume. Gently disconnect it with plastic tweezers, pulling the black tongue of the connector.

Now the body is completely dismantled. At this point, you can:

• 🔍 Inspect the charge for damage (blackened elements, bloated capacitors).
• 🔋 Check the voltage on the batteries with a multimeter (normal: 3.7-4.2 V on each cell).
• 🔌 Call me. USB-cliff-port.

⚠️ Warning: If you smell burns or see traces of melting on the board during the dismantling, do not turn on the device - this is a sign of a serious malfunction.

Diagnosis of malfunctions: what can break inside

After dismantling Xiaomi Power Bank 20000 mAh, it is important to correctly identify the malfunction.

Pay special attention to management fees (BMS) — It's responsible for balancing the charge, protecting against overheating and short circuit, and if you see blackened elements or bloated capacitors on the board, you'll have to replace it completely. In most cases, the board's repair is not cost-effective because of the complexity of soldering the chips.

To check the batteries, use a multimeter:

1. Set the constant voltage measurement mode (DC 20V).
2. Connect the probes to the cell contacts (red - plus, black - minus).
3. The voltage of a healthy cell: 3.7-4.2 V. If the indicator is below 3.0 V, the cell is deeply discharged and may not recover.

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If one of the cells is 0V, don't plug it into the charger, it could explode, and these batteries are disposed of.

Replacement of batteries: choice of cells and soldering

The 18650 batteries in Xiaomi Power Bank 20000 mAh degrade over time, losing capacity, and replacing them is the most common reason for disassembly.

• 🔋 Samsung INR18650-35E — capacity 3500 mAh, discharge current 8A.
• 🔋 LG INR18650 MJ1 — 3500 mAh capacity, discharge current 10A.
• 🔋 Panasonic NCR18650B — 3400 mAh capacity, high cycle life.
• 🔋 Sony VTC6 — 3,000 mAh capacity, but high discharge current (30A).

Important: Use only original cells from well-known manufacturers, cheap fakes can have undercapacity and poor protection, which will lead to repeated failure or fire.

Step-by-step replacement of batteries:

1. Seal off old cells. Carefully disconnect the wires from the battery terminals, remembering the polarity. Use a soldering iron to keep tracks on the board intact.
2. Set up new cells. Connect them in series (plus the first cell to minus the second) with nickel tape or wires. Secure the unit inside the housing with heat glue.
3. Soften the wires to the board. Keep the polarity: red wire plus (B)+), black - minus (B-). Check with a multimeter that there is no short circuit.
4. Check the balancing. Connect the power bank to the charging and make sure that both cells are charged evenly (voltage on each should rise in synchrony).

⚠️ Warning: If you use cells with different capacity or wear, one of them will recharge, causing it to deteriorate rapidly or even catch fire. Always replace both cells at the same time!

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When soldering batteries, use low-temperature solder (with a melting point below 200)°C) to prevent overheating of cells, prolonged heating may damage separators inside the battery.

Repairs USB-port-board

If the power bank does not charge or does not give current, the problem may lie in the USB-port or charge controller, for diagnostics:

1. Call the port with a multimeter. In vertebrae, check the integrity of the contacts. VCC (food GND (If resistance is going to infinity, it's a cliff.
2. Check the circuit board for damage, black resistors, swollen capacitors or cracks on the tracks are signs of malfunction: 🔥 Mosfet (field transistor) - responsible for switching current. 🔄 Controller chip (e.g., controller chip, IP5306 or SY6970). 🔌 Safety: Can burn out with a short circuit.

Re-sweeten the damaged elements.

If you have experience with rationing SMD-You can replace the components with the faulty parts:

1. Heat the board with a hairdryer to 250°C (for welding chips).




2 Remove the old solder from the contact areas.




3. Install the new component while observing polarity.




4. Soak the contacts with a thin sting.

If the board is badly damaged (for example, the controller chip burned), it is easier to replace it completely. New boards for Xiaomi Power Bank 20000 mAh can be found on AliExpress or in specialty stores (price: 5-15)$). When replacing the board, firmware may be required if the new version of the controller is incompatible with older batteries.

Powerbank assembly after repair

Once the repair is complete, it is important to properly assemble the device to avoid short circuits or mechanical damage.

1. Check the insulation. Make sure that all bare wires and battery contacts are insulated with shrink tubes or tape. Pay special attention to soldering locations.
2. Secure the board and the batteries. Use double-sided tape or heat-glue to lock the components inside the case. Don't let them shift when shaken.
3. Plug in the button plume (if any). Carefully insert the plume into the plug on the board before clicking. Make sure the contacts are not bent.
4. Put the body together. Put the top and bottom together, pressing them until the characteristic snap of the latches. Twirl the screws (don't pull over so you don't rip the thread!).
5. Stick protective stickers. If you've taken off factory stickers, replace them with new ones, or use transparent tape to protect the screws from dust.

After assembly, perform the test:

1. Connect the power bank to the charge and check if the indicator is on.
2. Measure the voltage on USB-port (should be 5B) ± 0.2B).
3. Connect the load (smartphone) and make sure that charging is underway.
4. Check the temperature of the case – it should not be heated above 40°C.

⚠️ Warning: If the power bank doesn't turn on after assembly, take it apart again and check: Polarity of battery connection. Integrity of button plume. No short circuits on the board (call multimeter).

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After the battery is replaced, run 2-3 full charge/discharge cycles to calibrate the controller, which will help restore an accurate indication of the charge level.

Frequent Mistakes and How to Avoid Them

Even experienced craftsmen make mistakes when disassembling and repairing power banks, and here are the most common ones and ways to prevent them:

• 🔥 Short circuit in soldering. Cause: accidental touch of plus and minus contacts with the tool. Solution: Use dielectric tweezers and check with a multimeter for the absence of KZ after each soldering.
• 💥 Battery overheating. Cause: long-term soldering without refrigeration. Solution: Solve fast with heat sink (e.g., crocodile clamping»).
• 🔋 Use incompatible cells. Reason: install batteries with different capacity or wear. Solution: Always replace both cells with new ones that are the same in the model.
• 🔌 Damage. USB-The reason: excessive effort in the extraction of the board. Solution: Carefully pick up the port on both sides, do not pull the wires.
• 📉 Controller calibration is incorrect, cause: no full charge cycles after battery replacement. Solution: Recharge powerbank to 0%, then charge to 100% 2 to 3 times in a row.

If you make a mistake and the power bank stops working, don't panic. 80 percent of the time, the problem is solved by re-disassembling and checking connections, but if the charge burns or the batteries are inflated, the repair may not be cost-effective, it's cheaper to buy a new power bank.

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Before the first charge after repair, leave the power bank on a flat surface and watch it for 30 minutes. If the case heats up or hisses, immediately disconnect it from the grid!

FAQ: Answers to Frequent Questions