Introduction: How to Salvage and Repackage Old 18650 Li-ion Cells

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About: Hello! I'm a second year Engineering Science student at University of Toronto! I have been tinkering and creating electronics projects since middle school, and I'd love to share this passion with more people a…

From small battery packs to large EVs and powerwalls, 18650s li-ion cells are the heart of a variety of battery-powered devices. They're also amazing for hobbyists and creators alike in making portable projects like electric golf carts. Needless to say, being able to salvage and reuse many of these cells from old electronics can be incredibly cost-effective and environmentally friendly. Here, I'll document the steps, tips, and dangers of re-using 18650 li-ion cells from old electronics like laptops and power banks.


DISCLAIMER: Lithium ion batteries can be extremely dangerous and hazardous if handled poorly. Always handle them with care, and don't work with them unless you know exactly what you're doing. I'm not responsible for any accidents that may occur.

Supplies

Anyways, now that all the lawyers and the legal-freaks are gone, let's get down to business. Here are some of the tools and parts needed to do this:


  • Source of old 18650 cells (e.g. laptops, power banks, medical devices, etc) For this tutorial, I bought a pack of several medical battery packs from batteryhookup.com, who sell a variety of used battery cells from li-ion to LiFePO4 for incredibly cheap prices. I'd definitely recommend them if you don't mind paying an eye-watering amount for shipping and import fees to Canada :(
  • Snips/pliers to open up the battery pack and cut nickel strips
  • Heat gun
  • 18650 heat shrink tubing + tip sticker
  • Sandpaper/dremel with a sanding tip


Step 1: Disassemble the Old Pack (cAREFULLY)

Of course, this step will depend heavily on the type of battery pack you're working with, but regardless, you will have to somehow open up the old package to access the cells inside. Prying, heating, and destructively cutting the enclosure could all be valid methods of opening, but special care must be taken to not puncture, short circuit, or otherwise harm the 18650 cells. Be especially careful not to short out the batteries when using metal tools such as pliers or cutters. Only one side of the cell should be touching the metal tools at a time. It might be wise to do this away from any flammable materials - preferably on pavement outside.


If the cells are being stubborn or it was heavily glued, it may be easier to carefully slice open the cell's shrink wrap, then pull out just the bare cell itself. Again, don't put too much pressure on the razor blade to ensure the cell is not being cut.


Upon pulling out the cells, it will likely still have some nickel strips still attached to the ends. Try to cut it off as flush as possible to the surface, as this will make polishing much easier later on. Don't pull the strip off, as this may puncture a hole through the cell.

Step 2: Gather All the Cells and Inspect Them

Once you've pulled them all out, it's time to inspect each one, one by one, in order to check for any physical imperfections or damage that could've occurred while salvaging the cells. You're looking for any dents, scratches, or holes on the cell. See the above picture for an example of a dented cell. Even cells with small dents shouldn't be used at all and discarded properly for utmost safety.

Step 3: Polish the Ends

Even if you cut the nickel strip as flush as possible, there's usually some residue left on the cell. This could cause issues later when trying to spot weld the cells for future use due to the uneven surface. Hence, I polish the ends using either sandpaper or a powered dremel with a sanding tip. If you're using a power tool, ensure proper safety measures and only dremel where the nickel strips are. Oversanding could potentially puncture the battery, so be cautious to only sand off the strip residue. There will be metal shards, so wear a mask and do this in a well-ventilated room.

Step 4: Apply Insulation Sticker

To prevent short circuits between the anode and cathode, you must apply a sticker on the cathode side of the cell (side with the nub pointing out). Grab these stickers and stick it on!

Step 5: Heat Shrink Wrap

The (second) final step is to wrap the bare cell in heat shrink wrap. Watch the video for how to do this. BE VERY CAREFUL OF THE HEAT FROM THE HEATGUN! You should wear gloves or prop up the cell so that you don't have to hold the cell while heating like I did in the video. Too much exposure to heat can cause damage or fire to the cell.

Step 6: Test the Capacity of the Cell

Once that's done, you may also want to get a battery capacity tester. Then, you can check the capacity and write it on the side of the cell to keep track. This way, you can group the cells by capacity to make series connections in a battery pack. Another article on how to make a battery pack will be uploaded soon. When charging the cells again for the first time, you should closely monitor it for any signs of heat or malfunction. In that case, discard the cell appropriately. Once charged, you should also leave the cell for a few days to see if the voltage has dropped significantly. If it has, then also discard the cell as it means there is a leakage.


You should aim to charge it to around 3.6v, as this is around 50% charge and is optimal for longterm storage. It may be safer to discharge them further when creating new battery packs though.

Step 7: Make Cool New Projects!

Equipped with the arsenal of 18650 cells, you're now free to make the projects that your heart desire! I've made several battery banks to an remote electric golf cart with the cells shown in this article, so you should check them out on my profile.

Happy building!