# How to Fix a Power Bank's Battery

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Hi everyone,

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

For this project you will need the following items and tools:

## 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!

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## 3 Discussions

I like your idea, i would like to increase it's capacity by adding more cells in parallel if i got the power bank circuit.

I like the idea of swapping out a battery and using the cicuitry of the powerbank but IMO you jump too quickly to the saw, pretty much destroying the case, with a bit of patience and the right combination of knife blades and plectrums you should be able to prise open the case without to much damage, making it reusable.

Also I'm confused by the voltage mentioned, I thought a 18650 battery was 3.7v stepped up to 5v for the USB output by the powerbank circuit?

1 reply

Thank you for the comment! I used the saw just because the enclosure of my power bank was a unique piece of plastic and so i hadn't any other way to open it. But you are right, maybe other power banks can be opened with a small screw driver and a bit of patience. I know I have demaged the enclosure but I will rebuilt it in another project. 3.7V is the nominal voltage of a Li-ion battery but it can go from 3 to 4.2V.