Lithium Ion protection circuitry?

I was wondering....
The protection circuit for li ion cells in phones; is it a sort of regulator for the battery when charging? Or does it just stop the cell from being drained too far? I was wondering if I could use the circuitry from the prismatic li ions found in mobile phones for a 18650 battery....will the difference in capacity be a problem?

Chirpoff6 years ago
Here are two sites I found, don't know if it will help, but you can give it a try!

Have a nice day!