Massive USB Battery Bank Made From Recycled Chromebook Batteries

I made a USB battery bank out of recycled chromebook batteries.

Supplies

Batteries : I used the batteries from 11 old Chromebooks that were being sent to recycling. You will need to separate all the individual cells from each laptop. I ended up with 32 cells in my battery bank with one left over.

BMS Boards : The BMS (Battery Management System) Boards are required to ensure that all the individual cells will charge and discharge to the same voltage. This is necessary because lithium batteries have very specific voltages that they need to be charged to. I used 4, 4 cell boards.

Wiring : I had only needed maybe a few feet of 14 gauge speaker wire. This was because I was able to solder the batteries directly to each other. The wiring will also be used to connect all the USB power boards to the batteries.

Soldering Equipment : You will need a soldering iron and plenty of solder (the batteries use a lot)

Display : The display is completely optional but without it there will be no way to tell how much charge is left in the battery. I used one purchased from Amazon but any voltage display should work.

USB Ports : You can use any combination of USB voltage converters that you would like as long as they are rated for the voltage of your battery which in my case is ≈17 volts One. thing to be aware of is that they all need to be connected in parallel to ensure they all get the same voltage.

XT60 Connectors : It is important to be able to disconnect the batteries from each other to charge them. I used these connectors to allow for quick and easy connections wherever needed.

Switch : The voltage converters in the USB ports as well as the display will draw power from the batteries even when there is nothing plugged in so it is necessary to add a switch that will allow all power to be completely disconnected.

Step 1: Choosing Ports for Front Panel

Before you start this project it is important to know what components you will be using. This includes USB ports (Type A or type C), the voltage display, and any other extras that you might want to add to your project. I wanted to have lots of extra ports so that I could have many people charging their devices at the same time. I also chose the advanced display mostly because it looks cool, but it also allows me to quickly know how charged the battery is.

Step 2: Battery Wiring

The first step is to solder all the batteries together to make 4 separate battery packs. The cells I used were convenient because they lined up in a way that allowed me to directly solder them without using any extra wires. After all the batteries are connected, the BMS (battery management system) board and XT60 connector will need added. This will require a balance wire to be connected to the terminal on each side of the 4 parallel cells of the battery. Once you do all of this 4 times you will be ready to assemble the battery pack.

Step 3: Battery Assembly

Now that you have soldered the batteries together, it is time to assemble all the batteries into one large pack. First, line up all the batteries as shown in the first picture. Once you get them all lined up, use clear packing tape to tape everything together. You want the tape to be as tight as possible to prevent the batteries from expanding during use.

Step 4: Gluing the Batteries

This is also a good time to use silicone glue to cover all the electrical connections and prevent anything from shorting. Once you have given the glue time to dry, use more clear packing tape to protect all the internal connections of the batteries leaving just the XT60 connectors out.

Step 5: Connecting the Batteries Together

Since all the batteries are currently still separate, you will need to make a connector to connect all of them in parallel. This is the adapter shown in the first picture which is made by the all the negative leads of 5 XT60 connectors together as well as connecting all the positive leads together.

Step 6: Making the Case

Now that all of the work is done for the battery, it is time to start building a case. I started by measuring and then building a model out of cardboard. This allowed me to know that all of my dimensions were correct for when I 3D printed the final case. I used a file from Thingiverse so I would be able to scale it to my dimensions. The model I chose also had pre-made holes to screw the lid on. The box itself should not need any modeling done besides scaling, so it can be printed after you determine how much you will be scaling it by.

Step 7: Making the Lid

The lid will need all the holes added for any components you wish to mount to the front. I chose an integrated voltage display that will allow the user to see the status of the battery and know when it needs charged. As far as USB ports you can use any combination you like but I chose to use 2 banks of cheap low-power ports paired with 2 high power ports for fast charging. To make holes, I measured the dimensions of the ports and simply cut the same sized sections out of the model before printing.

Step 8: Assembling the Case

The next step of this project will be to attach all the connectors to the lid of the case. It would be easiest to just use CA glue to attach all the connectors, but I used a 3D pen to reinforce the joints.

Step 9: Final Touches

The last thing to do is to attach the lid to the box and admire your new battery bank. My box has the holes pre-made to use M3 screws to hold the lid.