Xiaomi Power Bank 20000 mAh may be needed for many reasons: from replacing a bloated battery to repairing it. USB-But this process requires care, because inside the device are lithium cells, which, if mishandled, can cause fire or explosion. In this article, we will discuss in detail how to safely open the case, what tools will be required, and what to pay attention to not damage the internal components.
Mi Power Bank 20000 mAh models (e.g., Mi Power Bank, PLM03ZM, PLM04ZM or PB200LZM) They're similar in design, but they can vary in the type of mounting and the layout of the components on the board, and we'll look at the universal disassembly method that's suitable for most versions, and we'll also point out some key differences. If you have never before disassembled electronics, we recommend that you first familiarize yourself with the basics of working with lithium batteries - this will save you from mistakes.
We warn you beforehand that disassembly will void Xiaomi warranty if it is still valid, and not all parts (such as the original 20700 batteries) are easy to find on sale — sometimes it is easier to buy a new power bank than to restore the old one.
1.Preparation: security tools and measures
Before you start disassembling, make sure you have everything you need. Here's the minimum toolkit:
- 🔧 Plastic mediators or shoulder blades (to open the body without scratches) Metal screwdrivers can scratch the plastic.
- 🔨 Thin cross screwdriver (usually screws in Xiaomi Power Bank - type) PH00 or PH0).
- 🧲 Magnetic mat or screw container (so as not to lose small details).
- 🔋 Multimeter (to check the voltage on the battery and board).
- 🧤 Gloves and safety glasses (in case the battery is damaged).
Also, prepare your workspace: it should be clean, well-lit and free of static electricity (ideally an antistatic mat). Never disassemble a powerbank on a soft surface (such as a sofa or carpet) - screws or parts can get lost, and static electricity will damage the board.
⚠️ Attention, if the power bank case is inflated or deformed, it's a sign of a bloated battery, and if you disassemble the device, it's dangerous, lithium cells can ignite.
Before disassembling, completely discharge the power bank (up to 0%) - this minimizes the risk of short circuit. If the battery is no longer holding charge, wait 24 hours after the last charge - this will give time for self-discharge of the capacitors.
💡
If the screws in the power bank are "stiff" and do not unscrew, moisten them with isopropyl alcohol (not water!) and wait 5-10 minutes. This will help dissolve the oxides without damaging the thread.
2. Opening of the body: step-by-step instructions
The Xiaomi Power Bank 20000 mAh has two halves held together by latches and screws, and most models have screws hidden under stickers or rubber legs.
- Remove all the stickers from the case (usually located on the ends). Underneath them you will find 2-4 screws. PLM03ZM and PLM04ZM The stickers may be under the ports USB and micro-USB.
- Unscrew all the screws and gently put them aside. In some versions, the screws can be of different lengths — remember which one from where.
- Put a plastic mediator in the gap between the halves of the case (better start from the side where there are no ports). Carefully drive the tool along the perimeter, breaking the latches. Don't apply excessive force - the plastic is fragile!
- When all the latches are snapped, remove the top cover. Be careful, it may be glued to the indicator panel. LED-lamp-light).
If the body doesn't respond, don't try to break it. You may have missed a screw or a latch. PB200LZM Sometimes there is an additional screw QR-code on the bottom - check it out.
☑️ Pre-opening checks on the hull
After opening, you will see the internal structure:
- 🔋 Two 20700 batteries (or one larger one in older models) connected in parallel.
- 📱 Control board with charge/discharge controller (usually marked) BQ25703 similarly).
- 🔌 USB-Type-A and/or Type-C ports soldered to the board.
- 🔦 Indicator panel with 4 LED and switch-on.
3. Disconnection of batteries and boards
Now you have to disconnect the batteries from the control board. This is the most critical step, because a mistake here can lead to a short circuit.
- Look at the battery connections to the board. These are usually two wires (red plus, black minus) soldered or connected through a connector.
- If the connection is on the connector, carefully disconnect it with a plastic spatula. If soldered, use a soldering iron with a thin sting (power no more than 30 watts).
- Before you puff off, check the multimeter voltage on the battery terminals. ≤ 3.0V (If the voltage is higher, discharge the batteries through a resistor (e.g. 10 ohms).
In Xiaomi models, batteries are often glued to the body with double-sided tape. To remove them, gently tuck the edge with a plastic card and pull up. Don't bend the batteries or drop them!
⚠️ Attention, if you notice swelling, electrolyte leakage or rust on your batteries, stop working immediately. These batteries can't be recycled, they need to be disposed of at special reception points.
The control board is usually attached to the body with screws or latches. Unscrew them and carefully remove the board. USB-Ports can be fragile. In Quick Charge models, for example, PLM05ZM) The board may have additional elements to stabilize the voltage.
What if the batteries are interlocked?
Diagnostics of malfunctions
Now that the device is disassembled, you can determine the cause of the failure, and here are the typical problems and their signs:
| Symptoms. | Possible cause | Decision |
|---|---|---|
| No charge from the grid. | Damaged. USB-port | Check the multimeter chain from port to board, if necessary, replace the port |
| It's discharged fast. | Battery wear or high self-discharge | Measure the capacity of the batteries, replace with degradation |
| Not included, LED burnt | Chain break or controller failure | Call the charge, check the fuse (if any) |
| Heated when charging | Short circuit in the battery or overloading the controller | Urgently shut down, check the batteries for bloating |
Use the battery to check the batteries USB-Tester or multimeter in capacity measurement mode. Normal voltage for Li-ion battery 20700 - 3.6–4.2V. If the voltage is lower 2.5V, The battery is deeply discharged and may not recover.
Charge controller (usually a chip) BQ25703 Or similar, it's responsible for overcharging, short circuit, and overheating protection. If the board is visually damaged (blackened elements, bloated capacitors), it's got to be replaced. There are universal boards for power banks on sale, but they may not support Quick Charge or Power Delivery.
5. Battery replacement: selection and installation
If the original Xiaomi 20700 batteries fail, they can be replaced with analogues.
- 🔋 Type: Li-ion or Li-Polymer (depending on model).
- 📏 Size: Diameter 20.5-21 mm, height 70-71 mm (standard 20700).
- ⚡ Capacity: At least 4000 mAh per battery (in the power bank there are two connected in parallel).
- 🔌 Discharge current: Not lower 10A (fast-charging).
Suitable analogues:
- 🔹 Samsung INR20700-40T (4000 mAh, 30A)
- 🔹 Molicel INR20700A (4000 mAh, 30A)
- 🔹 LG INR20700 M50LT (5000 mAh, 10A)
Before installing new batteries:
- Check their voltage with a multimeter - it should be 3.6–3.7V.
- Seal the batteries to the board, keeping polarity. Use flux for aluminum if the wires are aluminum.
- Isolate contacts with a shrink tube or tape.
⚠️ Attention! Do not use batteries with different levels of charge or capacity, this will lead to imbalance and rapid degradation.
After replacement, assemble the power bank in reverse order. Before final assembly, check the operability:
- Connect to the charging and make sure the lights are on.
- Measure the voltage at the exit USB — it should be 5V ± 0.2V.
- Check the capacity with the help USB-Tester (should be close to 20,000 mAh).
6. Repairs. USB-port and control board
If the problem is not batteries, but in USB-Ports or Controllers, do this:
Replacement USB-port:
- 🔌 Seal off the old port with a soldering iron, previously removing the solder with overflower.
- 🔧 Install a new port (e.g., Type-C with Power Delivery support) by following the setup.
- 📏 Check with multimeter the absence of short circuit between contacts.
Repair of the management board:
- 🔍 Examine the charge under the magnifying glass for microcracks or detached tracks.
- 🔥 If burned elements (resistors, diodes) are found, solder them and replace them with similar ones.
- 📡 To replace the controller (e.g, BQ25703) You will need hot air (soldier station) and experience with the SMD-component.
In models with Quick Charge 3.0, for example, PLM05ZM) The fee may have an additional charge DC-DC If it's burned, it's easier to replace the board altogether, because it's a complicated circuit to repair yourself.
💡
If the power bank does not turn on after replacing the batteries, check the fuse on the board (usually marked) F1). It can burn out if you short it out. Replace it with a similar one with the same face value (usually a short circuit). 3A–5A).
7.Assembly and test
After repair, collect the power bank in reverse order:
- Put the batteries in place, secure them with double-sided tape.
- Connect the control board to the batteries, observing the polarity.
- Secure the board with screws and install an indicator panel.
- Close the body, snapping all the locks, and twist the screws.
Before the first use:
- 🔋 Calibrate the battery: completely discharge the power bank, then charge to 100%.
- 📊 Check the real capacity with the help USB-Tester (must be at least 18,000 mAh).
- 🔥 Make sure the body does not heat above 40.°C when charging.
If the power bank is unstable after assembly (for example, it shuts down when loading), check:
- 🔌 Battery soldering quality and USB-port.
- 📉 Controller setup (some boards have adjusting resistors for voltage calibration).
- 🧲 The presence of magnetic interference (for example, if metal sawdust was near the board).
8. Frequent mistakes and how to avoid them
Even experienced masters sometimes make mistakes when disassembling Xiaomi Power Bank 20000 mAh.
| Mistake. | Effects of consequences | How to avoid |
|---|---|---|
| Use of metal tools to open the body | Scratches, chips, short circuit when touching the board | Use only plastic mediators |
| Disconnecting batteries without voltage check | Short circuit, fire. | Always check the multimeter before you drop. |
| Replace only one battery in a pair | Unbalanced, rapid degradation | Change both batteries at the same time |
| Overheating at soldering | Damage to board or batteries | Use a soldering iron with power ≤ 30 Watts. |
Another common problem is the loss of screws when disassembling. Xiaomi Power Bank usually has 4-6 screws, and they can vary in length, so you don't confuse them by taking a picture of their location before unscrewing them, or using a magnetic mat with a marking.
If the power bank doesn't turn on after assembly, don't panic. Go back to the diagnostic step and check:
- 🔌 Correct battery connection (polarity!).
- 📡 Integrity of tracks on the board (especially around the USB-port).
- 🔋 The presence of voltage at the input of the controller (should be) ~4.2V battery-powered).
💡
If the battery is not being replaced, the power bank is probably not holding the charge, and 80 percent of the time, the charge controller is the problem.