4000mAh - USB Powerbank Out of the Trash Can

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.

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!

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!

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.

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.

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.

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!