Bjorn Scrap Battery Hack

Key Takeaways

Guys, I have a serious problem. I'm addicted to hoarding scrap electronics. I see electronics being thrown out. I cannot help myself from saving them to either hack or force spare parts. But today, we're going to put those scrap parts to good use by adding a lithium ion battery, charge controller, and voltage regulator to my Bejorn to make it mobile and portable. I showed the steps how to build your own Bejorn and use it in a previous YouTube video. So, if you haven't seen that yet, I'll drop a link to it down below. Up until now, I've just been using my Bejorn plugged into the wall. However, I'd really like to make it portable. There's actually some great pre-built solutions already if you want to add a battery to your Raspberry Pi, like this Wave Share battery hat that's actually designed to work in conjunction with the e-aper display. And then you can either 3D print yourself or buy some really cool 3D cases if you want to make a really neat and professional looking solution. However, I think I've got all of the scrap parts saved here to do it myself and I want to take you along on the journey of how I'm going to build this. Let's hop over to the lab now and take a look. My initial idea and what actually gave me the inspiration for this project was to try and repurpose the electronics and battery from this disposable vape pen that someone littered in my front yard. You may have actually seen the short where I took it apart and tried to sniff out some of the eye to see traffic. I recalled that it had a 5V pad, so I thought it might have a boost circuit and 5V regulator that could power a Raspberry Pi 0 if we added in a bigger battery. Unfortunately, after some testing, it looks like that 5V pad is not actually connected and the microcontroller just runs off of the raw battery voltage itself. For a small microcontroller, this is fine and is inside of the operating range that it can tolerate. However, a Raspberry Pi needs a steady 5V input to be able to function properly. If you're not familiar with lithium ion batteries, their voltage starts usually at around 4.2 volts and then over the span of using them and as they dissipate, that voltage actually drops all the way from 4.2 down to about three when they are dead. To run electronics like our Pi or even things like a cell phone that need that constant 5 Vs, you require another circuit that can actually take the input of the battery in its operating range. So, all the way from something like 4.2 volts down to 3 volt and boost it up to 5 volts and keep it steady at that 5 V. Luckily, since the vape pen idea didn't work out, I've actually got that entire circuit scrapped from an old power bank where the battery died on it. And I think we can repurpose that here. I've also got a handful of identical lithium ion batteries that I scrapped from a drone. And I think if we connect some of these in parallel, it will give us enough juice to be able to run our Raspberry Pi. Pay attention to this part if you are thinking about trying this at home. If you want to connect lithium ion batteries in parallel, it's really important to make sure they are the same capacity and starting at the exact same voltage within about 0.05 volts when you hook them up in parallel. Ideally, you should be using the exact same brand and part for all of these batteries. Now, the reason for this is because if you actually hook up different capacity batteries that are at different voltages, you can actually get additional currents that are then just running between those batteries and this can damage the batteries or even in some scenarios start them on fire. Not good. I had what is one of my favorite DIY project cases lying around, a used Altoids tin. So, the next step was to solder all of the batteries together and then find a way to organize them and fit them inside of the Altoids tin. Next up, I did a dry test with that circuit board from the power bank just to make sure that it was going to work with those batteries and also be able to provide enough current to power the Pi. Luckily, it was able to and a quick check of the voltages and everything was steady. Next up was to figure out how to fit that circuit board inside of the Altites tin. I thought it was going to fit perfectly and it was so close, but it looks like we are going to have to hack up the tin to have a little bit of the PCB hanging out. But that's okay because that's where the switch to actually turn on those indicator lights that show the charge level is. And this will also have the lights on the outside of the tin so that you can easily see the battery level without having to open it up. For a bit of a hack job, it's actually turning out okay so far. To keep everything self-contained inside of the Altoids tin as best as I could, I didn't want to have to be plugging in a USB cable. So to get around that, I actually went straight to the 5V and ground pins that were on the USB connector. I was able to solder some wires to the 5V out and the ground and then was able to connect those directly to the pins on the Raspberry Pi and solder those there so that the e-aper display could still fit on top over them. It was at this point that I remembered I actually wanted to put a switch in here as well so I could turn off the Pi and have it always be draining that battery. So, I soldered in a switch as well. Another quick dry test and everything is looking good. We can see Bejorn cycling through and running. And now we're ready to just package the rest of this up. Cut a hole in the top of the Altoids tin and get this all put together. I was really hoping that I could get the screen flush with the top of the Altoids tin once I cut out the opening. However, there was just too much space taken from those batteries. So, I had to cut it out so it protruded a bit. And that's what the finished product turned out to be. Again, with these DIY scrap bin builds, they don't always turn out with the best aesthetics, but to be honest, I kind of like it that way sometimes. While I'm putting this all together, now is a great time to tell you that if you like this hardware stuff and you want to learn about hardware hacking, then you should definitely check out the beginners's guide to IoT and hardware hacking on the TCM Security Academy. I'll put a link to it down in the description below. This is a course that I created that walks through how you can actually hack IoT devices that you have inside of your house or lying around. even going down to the hardware level of connecting to different headers and interfacing with those. It's definitely worth checking out. So, once the build was done, everything worked great. I tested it out and I was actually getting a couple hours of run time off of those four scrapped batteries. It charges fine. Everything works great. And to be honest, personally, I kind of like the DIY aesthetic myself. If you enjoyed this video, make sure you're subscribed to the TCM Security YouTube channel. And again, if you want to build your own Bejorn and you haven't checked it out yet, I'll drop a link to the full video we have that walks through every step on how to put together your own Bejorn. Thanks for watching.