In a previous video, I tried and failed to repair a power bank that I found on the flea market and was water damaged. In an attempt to find a replacement board for it, I stumbled upon the LX-LBU2C module and bought one to try and fit it inside the enclosure.
This was not a good fi, so instead I decided that I'll build completely new powerbank using the module and some salvaged 18650 cells that I had from old laptop batteries.
LX-LBU2C Module Review
The LX-LBU2C power bank module is a compact and affordable solution for DIY power bank projects. Its straightforward design supports multiple lithium-ion 18650 batteries wired in parallel, offering 5V/2.4A USB output—enough to charge smartphones and small devices efficiently. The built-in protection against overcharge, over-discharge, and short circuits adds a layer of safety, making it beginner-friendly. However, its lack of USB-C output or fast charging may disappoint those seeking modern features.
Performance-wise, the module delivers reliable power conversion with minimal energy loss. The included battery level indicators (four LEDs) are handy for monitoring remaining charge, though they’re not precision-calibrated. While it handles standard 18650 cells well, performance drops slightly with lower-quality or heavily used batteries. Soldering points are well-labeled, but the thin PCB requires careful handling during assembly.
For under $5, the LX-LBU2C is a solid choice for basic power bank builds. It’s not cutting-edge, but its simplicity, safety features, and cost-effectiveness make it ideal for first-time DIYers or emergency power backups.
Power Bank Enclosure
One of the greater challenges for DIY projects, yet alone power banks, is figuring out the enclosure for them. Luckily, I was able to find an enclosure online that was made specifically for the LX-LBU2C module by Slava Strunov.
This enclosure is intended for 8P configuration where you have 8 cells in parallel, but since it is designed in multiple parts, I decided to use just half of that and build a 4P battery pack.
The enclosure is 3D printed and I printed it at home but if you don't own a 3D printer, you can use the great 3D printing service that PCBWay offers to get all of the necessary parts.
LED Flashlight Circuit
Some of the commercially available power banks often include a flashlight directly on the power bank. This is really handy for power outages or when using the power bank on camping trips but since I already have a lot of flashlights, I decided I'm gonna build a special kind of flashlight with red light.
When stargazing at night, using a red flashlight—rather than a white one—helps preserve your natural night vision. White light causes your pupils to constrict, making faint celestial objects harder to see, red light has a longer wavelength that minimally disrupts your eyes’ adaptation to darkness. This allows you to read star charts, adjust telescope settings, or navigate your surroundings without sacrificing your ability to observe dim stars, nebulae, and galaxies. Many astronomers and outdoor enthusiasts rely on red light to maintain optimal visibility during nighttime observations.
The power bank enclosure has space for 7 LEDs, and to power them from the 5V output of the module, I used two 68 Ohm, 1/4 Watt resistors in parallel to get a 34 Ohm, 1/2 Watt resistor. This should limit the current through the LEDs at around 12 milliamps and dissipate around 250 milliwatts on the resistor.
The original circuit called for a22 Ohm resistor for 20 milliamps on the LEDs, but that would have cause a lot of energy to be wasted as heat.
Testing the 18650 batteries
Before you start building any battery pack, it is very important that you test your battery cells and make sure that they are all at the same voltage. Since we will be connecting the batteries in parallel, if you ever connect a fully charged battery to an empty one, huge current fill flow between them that might damage the cells or even cause a fire.
My cells were at around 4.06V so I continued to connect them together and build the pack.
Building the pack
Since we are making a 4P battery pack, we need to connect all 4 battery cells in parallel. This is best done with a spot welder and some zinc strips but since I do not own a spot welder, I'm going to solder the batteries together. I know that this is not ideal as excessive heat might damage the batteries chemistry but I have no other option right now.
To make sure that I only keep the heat on for a minimal amount of time, I cleaned the battery contacts and I also applied some solder paste to flow the solder easier.
Since my cells are taken out of old laptop batteries, whenever possible, I left a small piece of the original spot welded zinc strips and I used them to solder on. This way, the battery is only exposed to minimal heat minimizing the risk of damaging it.
Once the pack was soldered together, I also soldered the output leads to the power bank control module and I also soldered the LED flashlight wires to the output on one of the USB ports.
Power Bank Tests
After I connected everything and closed of the enclosure with the screws, I continued to test all of the functionalities of the power bank. I first tested the built in flashlight, followed by charging devices from it and also charging the power bank it self.
Everything worked as expected and I now had a functional power bank that will suit us well on our camping trips.
Making DIY power banks is an easy and rewarding afternoon project especially if you can source the battery cells from old equipment and give them a second life. The LX-LBU2C module turned great and although it does not have fast charging it will do for powering projects, providing backup power or just power our camping lights.
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- LX-LBU2C Module - https://s.click.aliexpress.com/e/_oC6Dy6H
- KCD11 Mini Switch - https://s.click.aliexpress.com/e/_oCocI1j
- JCD Soldering Station - https://s.click.aliexpress.com/e/_oB2HNcV
- Assorted LEDs - https://s.click.aliexpress.com/e/_omPUU81
- 3D printer - https://s.click.aliexpress.com/e/_oDS88CZ
- Screws - https://s.click.aliexpress.com/e/_oop739R
- Resistors - https://s.click.aliexpress.com/e/_olffyd7
- Bench Power Supply - https://s.click.aliexpress.com/e/_oFPVKqd
- RD6012 Step Down Supply - https://s.click.aliexpress.com/e/_opWHYff
