recycle laptop 18650 lithium batteries in a DIY power bank

If you could look inside an old replaceable laptop battery pack like this you’d find 4 or 6 cells. Usually the cells are 18mm diameter, 65mm long and are called 18650 lithium batteries. Each 18650 battery is rated at around 3-4 volt so if you multiply 6 cells x 3v you’ll get a figure close to the voltage of the laptop charger and the battery pack i.e. around 19v.

If your battery fails to hold charge it is unlikely that the pack will work even if you replace the cells. The way I chose was to recycle the battery pack and to buy a third-party replacement pack from a respectable supplier for £15. You could buy the official replacement for more money but I prefer not to pay that price. Although the original battery has failed, it’s possible that the 18650 cells in the battery pack work well. What may have happened is that the battery electronics have decided that the battery is no more.

To recycle the batteries cut the glued seam around the pack above. Your knife should point vertically to cut the glued seam not inwardly towards the batteries inside.

(If your laptop is the slim, modern type the battery pack will have flat cells instead and you can usually identify 4 or 6 flat cells under the casing. There may be other cases to recycle these ‘polymer batteries’. )

Buy a DIY power bank for 18650 cells

Fortunately ebay is on hand. You can buy cases that will hold and charge 18650 batteries to give you a portable power bank for your phone. The cases may hold one, two, four, six or more cells. Some cases feature LCD screen, flash light and more. Anyway, get that ordered.

Assemble your DIY power bank

Surprisingly the power bank doesn’t come ready assembled! I was a bit thrown when I saw the bits above and I wondered how to fit the four 18650 cells that I’d recycled from the failed HP laptop battery. The video below by ‘electronic guru’ pretty much explains it but here’s what to do.

  • Use a meter to check each battery has 3-4v and mark the + and – on the cells. Tape the batteries together side-by-side, with all the plus ends together.
  • See the second video for a way to wire the batteries in parallel. The batteries are wired in parallel because you want 3-4v. You don’t want 19v.
This is the case that I bought. I prefer the battery soldering technique in the video below.
Dreadful case but the soldering is good.

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