Xiaomi Power Bank 20,000 mAh Disassembly: A Complete Guide with Photos and Expert Advice

The seemingly compact but powerful Xiaomi Mi Power Bank 20000 mAh has become one of the most popular portable chargers due to its combination of capacity, charging speed and reliability. However, over time, even such devices fail: batteries inflate, connectors break or the indication stops working. If your overbank stopped holding the charge or refused to turn on at all, disassembly can be the first step to diagnosis or repair.

In this article, you will find detailed disassembly instructions taking into account all the nuances of the 20000 mAh model (including versions of the model). PLM04ZM, PLM05ZM, PLM12ZM), And we'll also talk about how to replace the components, check the control boards, and avoid common errors, and we'll talk about what tools you need, how to avoid damaging the body when you open it, and what to do if you find corrosion or bloated batteries inside, and we'll focus on safety. Incorrect disassembly of lithium batteries can lead to fire or explosion!

Preparation for disassembly: tools and security measures

Before you start a screwdriver, make sure you have everything you need. Disassembling Xiaomi Power Bank 20000 mAh requires care: the body is glued together, and inside there are high-capacity lithium cells that can not be pierced or deformed.

Minimum set of tools:

• 🔧 Plastic mediators (or guitar mediators) – to separate the glued parts of the body without scratches.
• 🔩 Cross screwdriver (usually) PH0 or PH00) — screw-in.
• 🧲 Magnetic mat or pallet – so as not to lose small details.
• 🔥 Refractory substrate (for example, ceramic tile) - in case the battery is damaged.
• 🧤 Gloves and safety glasses – Lithium batteries contain caustic electrolytes.

If you are planning to replace batteries, prepare:

• 🔋 New elements 18650 (for example, Samsung INR18650-35E or LG MJ1) capacityless 3400–3500 mAh.
• 🔌 A soldering iron with a thin sting (power up to 30 W) and solder.
• 📏 Multimeter – to check the voltage on batteries and board.

⚠️ Warning: If the body of the verbank is swelling or hissing, don't try to disassemble it! These are signs of an unstable chemical reaction inside the batteries. Place the device in a refractory container (for example, a metal bucket with sand) and leave it outdoors for 24 hours. Do not store near flammable objects.

Step 1: Opening the case - how not to break the latches

Xiaomi Power Bank 20,000 mAh has two halves glued around the perimeter, no screws on the outside, all held on glue and plastic latches, and the main task is to separate the parts without damaging them.

Procedure:

1. Place the verbank on a flat surface with the buttons up (so as not to damage the connectors).
2. Insert a plastic mediator into the gap between the halves of the body USB-Ports (there the glue is usually weaker).
3. Carefully drive the mediator along the seam, gradually separating the parts, and if you feel resistance, don't push harder, try from another angle.
4. When the body begins to "retract", walk the mediator around the perimeter to release the latches.

Typical Beginner Mistakes:

• ❌ Using metal tools (knife, screwdriver) – leaves scratches and can puncture the battery.
• ❌ The use of force at one point - breaks the latches, after which the body will not close tightly.
• ❌ Attempt to disassemble from the indicator side - there is a board located there, which is easy to damage.

If the body does not lend itself, you can slightly heat the seam with a hairdryer (temperature not higher than 60).°C) to soften the glue, but don't overheat, there's plastic parts inside that can deform.

Step 2: Removing control boards and batteries

After opening the body, you will see:

• 🔋 Two batteries 18650 connected in parallel (voltage 3.7 V, capacity of 10,000 mAh each).
• 📱 Microchip control board BQ25703A (or similar) responsible for charge/discharge.
• 🔌 Connectors USB (Type-A and/or Type-C depending on the model).

How to extract the fee:

1. Carefully disconnect the plume connecting the board to the batteries (usually a connector). JST 2.0).
2. Unscrew the screws that attach the board to the body (usually 2-3 screws). PH0).
3. Subdense the board with a plastic card - it can be glued to the case with double-sided tape.

How to remove batteries:

1. The batteries are secured in a plastic holder. Carefully squeeze the edges of the holder to free the elements.
2. Don't pull the wires! Unplug them from the board with a soldering iron or clippers (unless you plan on reusing).
3. Check the voltage on each battery with a multimeter. Normal: 3.7-4.2 V. If less than 3.0 V, the element is defective.

⚠️ Warning: If batteries have white coating (lithium oxides) or are bloated, don't try to charge them! These are recycled. When soldering new batteries, use low-temperature solder (melting point below 200)°C) to avoid overheating the lithium cells.

Step 3: Diagnosing faults – what could have broken

If the overbank is not charging or is not giving current, the problem can lie in one of three components:

Batteries:

• 🔋 Bloating is a sign of wear and tear or overheating. Replacement is required.
• 📉 Loss of capacity – if the voltage drops below 3.2V in 10-15 minutes, the elements are worn out.
• 🔌 Chain break – check the resistance between battery contacts with a multimeter.

Management fee:

• 🔥 Burnt elements – blackened resistors or chips (often due to short circuits).
• 📟 Faulty controller – if the board does not respond to the charging connection.
• 🔄 Oxidized contacts - clean with alcohol or eraser.

Connectors and wires:

• 🔌 Oxidation USB-Ports – a frequent problem when getting moisture.
• 🔗 Wire Break - Check Integrity From Batteries to Board.
• 🔋 Bad contact – sometimes it is enough to oversweeten the connector.

For accurate diagnosis, use a multimeter in vertebrae mode:

1. Check the integrity of the chain from USB-pre-payment.
2. Measure the voltage at the output of the board when connecting the charging (should be 5 V).
3. Make sure the batteries give out voltage on the board (check the holder's contacts).

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If the overbank is turned on but discharged quickly, try calibrating the controller: completely discharge it (before turning it off), then charge it 100% without interruption. Repeat the cycle 2-3 times. In 30% of cases, this restores the correct display of charge.

Step 4: Replace batteries - selecting elements and soldering

If the diagnostics show that the batteries are malfunctioning, they should be replaced. For Xiaomi Power Bank 20000 mAh, lithium cells 18650 are suitable with parameters:

• 🔋 Capacity: 3400-3600 mAh (less is not advisable to take).
• 🔌 Maximum discharge current: not less than 10A (fast-charging).
• 🔄 Type: INR (for example, Samsung 35E, LG HG2, Sony VTC6).

Step-by-step replacement:

1. Buy two identical items (the difference in capacity is not more than 50 mAh).
2. Charge new batteries to 3.7V with the 18650 charger (do not connect discharged cells to the board!).
3. Salt wires to new batteries while observing polarity (usually red — "+", black — "-").
4. Install elements in the holder and connect to the board.
5. Check the voltage at the exit. USB (5 V) before assembly.

Important nuances:

• 🔥 Don't solder batteries connected to the board! This can cause short circuits.
• 🧲 Use a heat-shrinking tube to isolate contacts.
• 📏 Balancing: If the battery voltage differs by more than 0.1 V, charge them separately to the same level.

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Using batteries of different capacity or degree of wear will result in uneven loading and rapid failure of the entire superbank. Always replace both cells at the same time!

Step 5: Control Board Repairs – What You Can Fix

If the problem is the board, you don't always have to change it completely, often just replace one or two items.

Fired fuse:

• 🔥 Sign: the power bank is not turned on, but the batteries are good.
• 🔧 Solution: find on the board an element with a marking F1 or FUSE (usually 3A/32V) and replace him.

Faulty charge controller (BQ25703A):

Oxidized contacts:

For the repair of the fee will need:

• 🔍 Loop or microscope – to inspect the tracks.
• 🔥 A soldering station with a hair dryer - for replacement SMD-component.
• 🧪 flux RMA-223 — solder.

⚠️ Note: If the chip is burned on the board BQ25703A or similar, its replacement requires experience with SMD-Without soldering skills, it is better to buy a new fee (for example, on AliExpress for the request “Xiaomi Power Bank 20000”). PCB"). Cost: about 500-1000 ₽.

Step 6: Building and Testing – How to Avoid Mistakes

After repairing or replacing components, collect the overbank in reverse order:

1. Put the batteries in the holder and connect to the board.
2. Secure the board with screws and connect the plumes.
3. Check the display (click the button - all 4 LEDs should light up).
4. Lubricate the edge of the body with silicone lubrication (for example, WD-40 Specialist) for better leakage.
5. Squeeze the halves of the body until the snap of the latches. Use clamps if necessary.

Testing:

• 🔌 Connect to charging - the charge indicator should burn.
• 📱 Connect the phone - check if the charge is going (current should be 1.5–2.4A).
• 🔋 Fully charge and discharge the overbank, keeping track of the time. Capacity should be close to 18,000-19000 mAh (heating losses and controller are normal).

If the verbank does not work after assembly:

• ❌ The display does not burn - check the connection of batteries to the board.
• ❌ Does not charge the device - measure the voltage on USB-exit (5 V).
• ❌ Fast discharge – perhaps one of the batteries is faulty or poor contact.

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After assembly, wrap the body of the superbank with insulation seamlessly for 2-3 days, which will help the halves lean closer to each other until the glue is finally grasped.

Frequent questions and answers