WARNING. Do this at your own risk…
If you are anything like me you have a host of devices that eat battery power. I know I do.
Tablets, Phones, Bluetooth headphones, Cameras etc.
Here is how I charge them cheaply. From eBay you can buy USB portable chargers that use 18650 batteries. The 18650 batteries are not something you can pick up at your local corner shop while you can get them online you might be throwing them away without knowing it.
Most laptop batteries count cells as how big the battery is but did you know the cells are normally 18650 batteries. Laptop batteries being designed to be charged and discharged a lot use high-quality cells as well. When you have outlived a laptop or the laptop has outlived itself the batteries may still be good. Sometimes even a bad batteries only has one bad cell.
This is where the warning comes. Break them open carefully and if unsure outside. If you split the batteries the outcome can be not pretty and if you have a girlfriend/wife you might not if you get acid on her nice coffee table smile
As I work in IT I get loads of laptop batteries heading for the bin (sorry safely disposed of) so I recycle the cells from them.
The images below are of an old Toshiba satellite battery that was heading the same way. Now it keeps me connected when away from grid power.