Reuse Old Phone Batteries As a Powerbank (earth Day Part 1)

Introduction: Reuse Old Phone Batteries As a Powerbank (earth Day Part 1)

About: Hi, my name is Jan and I am a maker, I love building and creating things and I am also quite good at repairing stuff. Since I can think I've always loved creating new things and thats what i keep on doing ti...

I guess you probably also belong to the majority of the worlds population that owns a smartphone and you probably had more than one during the past few years of smartphone evolution.

With them, come used lithium ion batteries that you can not just keep on using inside your new phone.
So you are stuck with useless batteries. I have 3 of them and I did not change my phone because the batteries were dead.

They did not get hot or start to swell so they are still able to power devices. The average lithium battery has 80% of it's original capacity left after 2 years of usage, which is the period in which I usually buy a new smartphone (not because of the better specs but because of major hardware issues).
And think about the energy that went into extracting the raw materials, producing the battery and shipping it.
Considering all that it would be a real shame to just let them slowly die or throw them away.
In this instructable and in my video, I want to show you how to build a device that enables you to repurpose your old phone batteries as a powerbank for newer devices.

Step 1: Materials

Let's start with what you will need for to build your own recycled powerbank.
The materials are:


  • a switch

The required working equipment consists of

  • a knife
  • a pair of pliers and a wire cutter
  • a soldering ion
  • a hot glue gun


  • a drill or dremel tool

Step 2: How Do the Boards Work?

Let's take a look at the lithium ion charging and protection board. It has three important functions.
The first is charging. Lithium ion cells have a certain charging pattern. When they are nearly full, their current consumption drops. The board will recognize that and stop charging as soon as the cell voltage reaches 4.2V.
On it's output the board features a protective circuit consisting of an over current and an under voltage protection. Such a protective circuit is already integrated in modern phone batteries and therefore not necessary but it will allow you to use unprotected cells like you would find them in old laptop batteries as well. The charging current of the board can be adjusted through a resistor. It should be somewhere between 30 to 50% of your battery's capacity.

The DC converter takes the dc voltage from the battery and turns it into a square wave that is send through a little coil. Through inductive processes a higher voltage is achieved. It is converted back to DC and can be used to power 5V devices.

Now you know what you are dealing with, time to start making .

Step 3: Planning

Before you begin to make the enclosure, take your measurements and make a plan.
My device is supposed to be held in place by the paper clamp, so it will be bolted to the enclosure. The two pcbs will sit on top of each other with the in- and output at the top and the battery pins at the bottom.
Some phone batteries tend to have a different polarity than others, so the device needs pins with interchangable polarity. To add this type of functionality I used the arduino pins and slots.
A piece of three slots with the middle metal connector ripped out and the 2 outer ones bend to the side can be used as a battery connector.
The counterpart will be a row of 4 pins with positive wires connected to the outer two and a negative wire connected to the two in the middle.
This way the polarity can be changed by plugging the battery connector in on either the right or the left side.

Step 4: Make the Enclosure Parts

Time to make the enclosure. For this you use your measuring tool to find the right with and use the knife to scratch the surface about ten times. Then you can keep in without the measuring tool and more force. When you are about half way through, place your pliers next to the cut and bend the materieal until it breaks.

When all the parts are cut out sand and test fit them. Fix them on a stable surface and start making the holes for screws, switches, inputs, outputs and pins using a dremel tool.

Step 5: Solder the Boards Together

Before you can assemble the parts you need to wire the boards. The shematic shows how they have to be connected. The small switch turns the dc converter on and off.

Step 6: Put the Pieces Together

Use hot glue to stick the pcb's together and to stick the onto one if the plastic pieces. Glue all the pieces in place and screw the clamp on.
Plug tha battery pins in and test it.
If it does not work, try plugging the charging cord in.

Step 7: Use It!

Now you have a new purpose for your old batteries.
My enclosure is definitely not the best looking solution but it's nice to show the concept. I bet that you can come up with some much more creative ideas.
In my next instructable and my next video, I will show you another way to recycle those old batteries so follow me to be up to date.

3 People Made This Project!


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25 Discussions

Is it necessary to use the switch?

Looks great man! I can't wait to try it. I just ordered the parts. Great video and good clear instructions. Thanks

woah, swolen batteries are a no-go zone. it is probably dangerously close to exploding now. dispose of it at a battery recycling center.

My new smartphone has a 3500mah battery which is enough to bring me through one day without recharging so I'm mostly using the device to keep my old batteries in shape. I'm also thinking about a version 2.0 with a proper enclosure for better handling.

isn't there already a protection board in these kind of batteries?!

2 replies

Yes, each commercial battery is a cell with a small PCB on its edge. If you need to use the raw cell, remove the battry covering and see the small PCB attached to the cell electrodes. As a guide for Samsung cells, the external metal body is the positive electrode, while the negative is wired through the PCB. Cut the electrodes carefully and remove the PCB. The new charging board replaces the same protection as the Samsung PCB which can be discarded (it has thermal and overvoltage chips on it).

did u mean that i can remove from my old smartphone all this components in this project? tq

Hi Jan, this is a great tutorial. Thanks for sharing it with us. pierre from New Mexico

Well done, excellent idea! One request for next time though, It would be fantastic if you could include links as to where to find the components required. (i.e. the protection board and the DC converter.) It would make life a lot easier and would slingshot your instructable from a 4 star to a 5 star. =D

1 reply

Thanks for the instructable and good work & ideas, however...

"And think about the energy that went into extracting the raw materials, producing the battery and shipping it. Considering all that it would be a real shame to just let them slowly die or throw them away."

I'm just wondering why you aren't using the phones until they die if you're so interested in saving energy and materials?

5 replies

lol, can you imagine still using a 486DX just cause it still "worked". I'm sure his logic isn't quite sound, but living in the world of old phones can be brutal when trying to run the latest software/games/os.. but then again, I'm picky ;-)

I understand, there are many good reasons for upgrading and getting something new or at least newer. My present cell phone is over 4 years old, with the original battery and this one was picked up after the last one died, stopped charging the battery, and after I charged the battery for six months by removing it from the phone and charging it with a Li-Ion battery charger I built. I just got tired of recharging it by having to remove the battery and all.

I still have a windows 97 laptop because it is the only PC I have that can upload/download data to a wide band scanner (radio) I have. The memory program does not work well with newer versions of Windows.

Thanks for your comment.
I think our planet and our world is amazing so we have to do everything to preserve it as it is for the most part, which is impossible but trying is better than doing nothing. Thats why I think about the ecological aspect in most of my decisions and I do only upgrade if major issues occur.
In my first smartphone the calling function did not work anymore even though I tried different things to fix it. The second one was the old smartphone of my sister and is now used by my mother Galaxy SII's are great. I became a heavy user during the past two years and use my smartphone as my main working device. It pretty much replaced my Laptop. This is why my latest upgrade was buying a UMI emax with a 3500mah battery, a fast processor and a huge screen.

Very good led_freak, you should have included that as well so we all knew you were passing them on or they died. That lends far more validity to your saving the battery Instructable.


2 years ago

Awesome!! I have a cemetery of still functionable mobile and camera batteries that a few years ago wanted to do something like this with. Couldn't quite make the discussion on here go the way I wanted, some how I made it seem like I wanted to repair them or something.

With other words - Thank you :)

1 reply

Please be careful which of thos old batteries to use. If the batteyr seems swollen (like a cushion) , discard it because it may have released hydrogen gas inside, and if overheated it can explode.