Before throwing a "defect" laptop battery directly in the trash can, i was curios what's the problem with the pack? The notebook just remained some minutes on before loosing power. I rip apart the battery and checked the LIon cells with my battery charger, they still have some capacity left and the pack has three of them! After searching the internet i found some nice cheap electronic parts to revive the battery and put them in a USB power bank for smartphones or raspberry pis.

This instructable shows how to make a easy cheap power bank out of a old laptop batteries, this should work with other types of batteries too.

Step 1: Get the Gold Out of the Trash

First open the battery pack gentle. Beware of making short circuits, this is dangerous because the battery pack still has power! Beware, maybe use plastic tools. I used a simple screw driver and a knife.

After removing the plastic enclosure i have three Lions Cells in my hand. They are parallel, so more capacity, yeah!

Step 2: Optional: Checking the Batteries

I used my battery charger to discharge the packs to check if they are really broken. I discharge to 3.7V, so no "real" discharge. Till the nominal voltage of 3.7V i was able to withdraw about 4000mAh of power. This is amazing!

Step 3: Adding Some Electronics - Loading Circuit

So now we have a battery pack with more than 4000mAh and 3.7V.

I used a loading circuit based on TP4056:

Loading circuit

The test shows, the circuits loads the battery full (i used a USB Amperemeter to check the current).

Just connect the + and - on the PCB with the + and - of the battery pack and connect a power source over USB.

Step 4: Adding Some Electronics - the 5V USB Regulator

We only have 3.7V, lets make 5V out of it with a easy step up regulator. As you can see in the picture it makes 5V out of the 3.7V of the battery and has a direct USB slot. Here you can connect your smartphone over a micro USB cable, or your raspberry pi :-)

Just connect the + and - of the battery to the + and - of the PCB, and it runs. Beware this circuit needs also current when there is nothing connected, so your battery will be slowly discharged. I added a switch between the battery and the electronic parts for disconnecting the battery from the electronic so the battery stay full loaded when i put it in the storage.

Step 5: Make a Enclosure

You don't need a 3D printer, you can use every enclosure you like. I designed a little enclosure with tinkercad.

I used a little screw to fix the lid of the box.

Step 6: Put Everything Together

Now I put everything in the enclosure. I added a simple switch between the battery pack and the electronic. So i can switch off the battery pack and no leakage current is drown by the 5V regulator. I used hot glue to glue the electronics directly in the enclosure, a easy and fast way.

That's it, now i have three power banks in my storage, fully loaded. I already used it to let my raspberry pi run in the nature.

Thanks for reading!

<p>I asked the owner of my local PC shop if he ever gets his hands on any dead laptop batteries, and he said he did. He said he would set them aside for me when he does, then give them to me the next time I come in!</p>
I see,you used a boost converter to step up/step down the voltage.(nice thinking cuz if you used a LM7805 Voltage Regulator,then it would not be efficient).
<p>also the 7805 would not work because you need more voltage (about 6-7V min. to get 5V out of a 7805). I had to use a boost converter from 3.7V to 5V, there was no other way :-) </p><p>I like the finished modules, a few years ago i had to make my own pcbs here. </p>
<p>By the way which model boost converter did you use and is it variable? And what is it's minimum and maximum current limit? Hope you answer:)</p>
<p>link is in the instructable : <a href="http://www.ebay.de/itm/DC-Buck-Regulator-9V-12V-24V-TO-5V-3A-Car-Charger-USB-Step-down-Power-Module-/281791346441?hash=item419c12b709:g:K7EAAOSwT6pV6ew~" rel="nofollow">http://www.ebay.de/itm/DC-Buck-Regulator-9V-12V-24...</a></p><p>Its a fix 5V 1A regulator. It has the same specs like a smartphone loading adapter (5V 1A is very common)</p>
<p>Did you break the 3 pack apart and test the cells individually?</p><p>I ask because I had a failed cell hiding in a good parallel pack. </p>
<p>Hi, no i just use each pack first on my professional charger to test if each pack is still alive, every pack had about 4000mAh till 3.7V so i guessed that every cell is ok. After i was sure that everything is ok with the pack i soldered the charge controller on it an loaded the whole pack over a night. </p>
<p>Great save of some still useful power sources. ☺</p>

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