I recently found this old 2200mah power bank but, after charging it, I discovered that it was completely dead. It was able to increase my phone's battery by only 10%. So I had two options: throw it away or try to replace the battery inside and make it new again.
Since I chose the second one, in this instructable I'll show you how to save money by replacing a power bank's battery.
Step 1: Theory
A power bank basically consists of a circuit board and one or more 18650 Li-ion battery connected in parallel. The circuit has two main functions: charge the power bank's battery when powered through micro USB and charge you phone in case of emergency. In my case I've just a single cell to replace but, in case your charger has more batteries, you only need more cells as the process is the same.
Step 2: Gather the Material
Step 3: Open the Power Bank
First of all we need to open the enclosure. To do this you can create a small opening on one side and, with the help of a small screwdriver, open the cover.
Otherwise, you can simply cut off from the top or the bottom with an hacksaw but pay attention to not cut the battery... IT CAN EXPLODE!
Step 4: Replace the Battery
At this point, in front of you, there are the battery connected to the circuit. Just out of curiosity, I tested the battery voltage in order to understand the cause of the problem and.... the voltage was only 1.03V! For those who don't know much about this type of battery, the voltage can vary from 3V (discharge battery) to 4.2V (completely charge battery). So I tried to charge it up and after 5 hours the circuit stop charging at a voltage of 4.2V. This means that the circuit works pretty nice while the battery has definitely a problem.
Now we are ready to change the cell. First we need to identificate the positive and negative terminals of the battery. Secondly, using a soldering iron, unsolde and remove the dead power source. After connect the positive side of the battery to the positive side of the circuit and using a small piece of wire do the same with the negative.
Step 5: Test and Conclusion
There you go! You have a new power bank
But...before exulting you need to test it. I plugged in the charger and the leds started blinking so the power bank is charging! After a couple hours I tried charging my phone and it's battery went from 26% to 100%...
I'm so happy for the success of this project and I wish it will be a useful guide for someone.
If you have any doubt, question or advise don't hesitate to write a comment, I really appreciate!