My father is using old laptop cells as portable power packs for many things; I usually send him all the dead laptop batteries I find, because in many cases ther

My father is using old laptop cells as portable power packs for many things; I usually send him all the dead laptop batteries I find, because in many cases there are only a couple of dead cells, the others are fine and can be reused. The problem is that 18650 cells (the ones you find in most laptop batteries) don't have an over-discharge protection circuit, so you can easily brick them if you don't add a protection circuit. You also have to be careful when charging them, as they can catch fire if you do it incorrectly.