Turn an Old Laptop Battery Into a 10 000 MAh Power Bank

There's not much you can do with a dead laptop, apart from salvaging the screen and the battery. In this Instructable, we will be exploring the latter option, and turn some salvaged lithium-ion cells into a functional 10 000 mAh power bank.

As a quick reminder, lithium-ion cells can turn into flames, when charged incorrectly or poked. So be extra careful if you decide to follow this tutorial, and if you're a kid, do this project with a parent.

Without any further ado, let's get crafty!

Supplies

Materials:

1x Old laptop battery

1x TP4056 Li-Ion charger module

1x Green 5mm LED

1x DC jack input (optional)

1x DC-DC step-up buck converter (I used an XL6009)

1x 2.2kΩ resistor

Glue

Solder

3mm MDF

Wire (I salvaged mines from an old ATX PSU)

Plexiglass (optional)

Tools:

Wire stripper

Hacksaw

Hot glue gun

Clamps

Soldering iron

Drill

Heat shrink tubing

Step 1: Opening the Battery

Laptop batteries are usually held together with small plastic pins, that are clipped together in the factory. So, to crack your battery open, you'll need the help of a large screwdriver and a bit of muscle force.

I've also encountered some laptop batteries, that are glued together, in addition to the pins. If that's also the case with your battery, break the joint with some kind of pliers. Do not use WD-40 or any other glue-dissolving agent, as it can permanently damage the lithium cells inside.

Make sure not to puncture the cells with the screwdriver, and proceed carefully.

After a few minutes, you should have in your possession a pile of 18650 batteries, spot welded together into a massive block. You remove any wires or PCBs, so that you end up with just the cells alone.

Step 2: Sorting the Batteries

As the battery comes from an old laptop, chanches are at least half of the cells have gone bad, so we'll have to sort those out.

Measure the voltage with a multimeter, and all the cells that are below 2.5V can be disposed of.

Charge up the good cells with the TP4056 charging module, or a dedicated 18650 charger if you have one. Monitor the temperature of the cells, and if they get hot, stop the charging immediately and dispose of those cells.

Finally, leave the charged-up cells sit for a week. Come back, and check the voltage again. If it has dropped significantly, throw those cells out too.

Out of all the cells I found in the laptop battery, only 5 were good.

Step 3: The Concept

The batteries will live in a rectangular enclosure, that will also house all the electronics. To make the visual more interesting, there will be a layer of plexiglass on top, to show the current charging state of the battery.

As I didn't have access to a 3D printer, the enclosure will be made out of plywood.

Step 4: Cutting the Encolsure

Trace out the dimensions of the battery pack + some extra room for the electronics on the side - and cut it out of the plywood board. To make it easier, you can first drill holes into the corners, and then use a hacksaw or a jigsaw to finish the cut.

Then, cut out the bottom and the top.

Step 5: Sanding

If all the layers of your enclosure are the same dimensions, good job! However, if they're not, use a belt sander to flatten them out.

Step 6: Painting

To make the small LEDs inside the enclosure stand out more, I painted the inside of the housing white to reflect light.

Step 7: Electronics

The circuit is very basic:

The lithium cells are charged by the charger module, which juices up the cells until they are full. Once the batteries are full, it stops.

The charging module then outputs the power to the buck booster module, where the voltage is boosted from the lower 3 to 4 volts of the batteries to a 5 volt that's compatible with USB charging. To make it accessible for USB devices, the 5 volts are delivered to two USB ports in a parallel circuit.

As we are using modules, the whole circuit can be made by just connecting them together.

I also added a power switch and a green LED power indicator with its 2.2kΩ resistor.

I also added an old-school DC power jack, as it can be used in any orientation, unlike the micro USB socket.

Step 8:

Solder everything together, while making sure not to overheat any components. Add heat shrink tubing where necessary, to avoid short circuits.

Step 9: Gluing

Glue the enclosure together, using you favorite glue.

Step 10: The Vinyl Wrap Experiment

In an attempt to make the sides cleaner, I covered everything with some white carbon fiber vinyl wrap.

As it turns out, in order for the vinyl to look clean, the surface underneath has to be flat. Otherwise, it will produce some nasty bubbles in the vinyl. So if I had to do it again, I would take more time making the enclosure, and leave it as is - plywood is very appealing too when nicely cut.