DIY USB Power Bank

A mobile power bank is very handy. When your electronic device runs out of power simply recharge it via USB port. I build one from scratch as it is cheaper and easily customizable. There are 2 USB outputs, one with 5V 2.1A and one with 5V 1A. Overall costs are around 15$. For this build you need

• dual USB PCB module
• 18650 batteries
• battery holders
• duct tape

It is a very easy build you just need to solder 2 joints. Instead of duct tape you might build your own wooden case or use a 3d printed one.

• The dual USB module has a negative and positive power connection: B- and B+. B- is the negative input, B+ the positive.
• The 18650 batteries need to be connected in parallel, meaning that all batteries are connected directly to the power connections of the board.
• In order to do so, solder the black wires (negative) to B- and the red wires (positive) to B+ of the USB module.I have used 3 battery holder but you can use more or less depending on how many batteries you are planning to use in your power bank.
• In order to avoid a short circuit make sure that you do not connect reversed!

• Before you set the batteries into the holders, make sure the are nearly identically charged.
• I used black duct tape to hold the batteries and the USB module together. However, you can also make a fancier case by using wood or a 3d printer.
• When using duct tape, make sure which shape you want before starting wrapping. I found It best to put the battery holders next to each other and wrap them first with duct tape. After that, I attached the USB module.

• Now you are finished and you can charge / discharge your power bank.
  • The module comes with charging overcharge protection, over-discharge protection, overcurrent protection.
  • The dual USB output delivers 5V 2.1A / 5V 1A

Have fun!