Mobile power bank DIY tutorial (picture)

 　　I was on business trips a lot for a while. I felt lonely on the long train rides. I had to use my mobile phone to surf the Internet to kill time. However, the battery was not strong enough and I often ran out of power. I couldn't buy a 10-8 yuan mobile phone battery as a backup. So I always wanted to make a mobile power bank to charge my mobile phone on the train. It was actually a battery + boost circuit + shell. I considered using a normal No. 5 battery or a 18650 lithium battery. This way, the battery can be easily found, which enhances the compatibility of the mobile power bank . I had already bought the boost circuit from the omnipotent Xbao, but I didn't have a suitable shell. Later, I picked up an A4 printer cartridge. At that time, I couldn't help but see a flash of lightning (it was actually raining at the time), which inspired me. Popular science: Toner cartridges are not toxic. Selenium is a trace element necessary for the human body, and the selenium on the surface of the cartridge cannot be absorbed by the human body.

　　Let’s look at the pictures and talk as we go.

　　Picked up A4 printer toner cartridge core

　　Cut it into the required length on the lathe. I didn't take a picture of the cutting process on the lathe because it takes a long time. The lathe can cut very smoothly.

　　This is the core, the boost circuit, from the almighty Xbao

　　With the shell and the circuit, I still need to process some accessories for assembly. For insulation, I used ash rods, which is a good wood. Weapon rods in the past were all made of this.

　　Interior Woodwork Collection

　　This is the front one. The round hole is the indicator light, and the square hole is the USB. The square hole is not easy to open, so I used a milling machine.

　　A4 cartridges are much thicker than 18650 batteries , so a battery barrel is made of wood for insulation.

　　Battery positive contact

　　The other side of the positive contact

　　The front cover + positive contact + battery barrel + circuit board after assembly

　　Insert it into the toner cartridge core cut to size. The positive pole of the circuit board is welded to the positive contact, and the negative pole needs to contact with the toner cartridge shell. In order to ensure reliable contact, a spring is welded to the negative pole of the circuit board. It's a good idea.

　This is what it looks like from the front when I put it in, my fat hands...

　　Now we need to process the threads on the bottom of the barrel. The wall thickness of the drum core is too thin, so we can only use aluminum alloy to process the threads and then embed them.

　　Then process the bottom cover, which is also made of aluminum alloy

　　Also weld the spring so that it can contact the negative terminal of the battery.

　　The effect of embedding threads in the toner cartridge core

　　Screw the lid on.

　　Put the 18650 battery in and see

　　The 18650 battery is thicker and longer than the AA battery. In order to use the AA battery conveniently, another battery conversion barrel is needed.

　　Compared with the flashlight, it can be seen that it is still relatively small.

　　Look at it alone, it's pretty nice, right? To open or close it, just twist the bottom cover and loosen it a little.