Add a Battery to a Power Bank to Double the Capacity

Hi guys. Some time ago the motherboard of my 5000mAh power bank broke and it actually melted and then, instead of throwing everything away and going to buy another power bank, I decided to yes, buy another 5000mAh power bank but take the battery of the old power bank and put it in parallel with the new one in order to double the capacity! So today let's see how to do it!

Material

• An old, broken power bank or battery cell with the same characteristics
• A power bank to add another cell to

Instruments

• Hot glue
• Tin soldering iron
• Insulating tape
• Flat head screwdriver (or flat pointed objects)
• Digital multimeter
• Scissors

Before we start, we need to unbox the new power bank. In the package we find the power bank and a USB-microUSB cable. The powerbank can be charged both from the micro-USB on the side and from the USB-C in front which is both charging and discharging. In addition, the three ports support fast charge.

Before starting to disassemble everything, I have to make sure that the powerbank works and for this I connect my phone with a normal UsbC cable and the charge starts.

We are ready to take everything apart!

First of all we will have to take the powerbank that has to give up the battery and open it (which was very simple unlike the new power bank that caused me a lot of trouble).

Once the old powerbank is opened, in addition to the card, which in my case was not there because I had thrown it away, as it had burned out, we find the battery which, as it is written above, has the same characteristics as there is. they were written on the powerbank packaging.

Obviously, since we will have to put this cell in parallel to the other cell, we must carefully measure the voltage of this cell in order to understand if it will be necessary to balance the voltages of the two cells or not.

This is important because if we connect a battery in parallel to another battery, if the two voltages are very different from the most charged battery to the most discharged one, a large amount of current will pass to try to bring the more discharged one to the same level. This violent flow of current can damage the cells.

The second step is to try to open the new power bank without getting hurt (as you can read from the title of the paragraph on instructables).

I say this because most power banks and many electronic products, especially if they have a battery inside, have to be made difficult to open by the factory. This is done to discourage changes (so not really for us) or for a safety factor.

In my case, I tried to insert a utility knife inside the power bank to create a thickness between the lid and the edge. Then I tried to insert a sharp screwdriver, the red one, remember well, the RED ONE and in the meantime, I also destroyed a USB port (which, however, we will see how I fixed it later.

After trying several times to open this damn powerbank, I realized that it was not possible when, with that red screwdriver, pointed specifically for this kind of work ... ZACC !!, I stuck it in my finger, creating a deep wound!

So I decided to open it, with a little force in my fingers, only in the upper part where the electronic board is housed.

Well, after getting hurt with a screwdriver, it's time to move on to the electrical part!

To do this, the first step is to balance the second battery with the first battery and then bring the second battery to the same voltage as the first battery.

Do you remember that we first measured the voltage on the battery in the power bank? well, this, which was 3.81, we will need to import it on a variable power supply to then connect to the poles of the secondary battery.

Then, connect the second battery to the power supply, set the voltage of the first battery (in my case 3.81V) and turn on the power supply, thus starting the charge.

Once the second battery is brought to the same voltage as the first battery, thus making sure that too much current does not flow from one to the other when we connect them in parallel, we cut a small piece of red wire and a small piece of black wire that can support at least 2A.

As you can see, when you wet the wire with tin, do it when the wire is straight or the sheath, which is elastic, when heated, will twist to return to its original position.

Now it's time to connect the second battery in parallel to the first and to do this you need to add some solder to the pin on the powerbank in order to better blend with the wire.

Now take the wire and place it with the pliers on the pin on the powerbank. Do the same thing with the other thread.

And done, you have added a second battery to your power bank by doubling the capacity.

To make everything more aesthetically pleasing, I took the cover of the old powerbank and placed it on the first battery in order to cover it.

Obviously, I had to cover the holes and here we are helped by the hot glue with which I closed all the cracks in the cover of the old powerbank.

At this point all that remains is to glue the two neighboring power banks and that's it!

And this was: How to double the capacity of a power bank by adding a cell in parallel.