Some protection circuits are built onto the bottom (-ve) end of the Li-Ion battery … This means that the live connection to the protection circuit is running from the positive end , down the side of the battery (under the wrap) … If the wrap is broken , possibly at a bottom edge , this connection can come into contact with the body of the torch , causing a short circuit.
If the protection circuit is at the top of the cell , then this connection is running from the negative end of the cell and is a less dangerous situation … In the case of a short circuit , the torch would switch on and run till it was noticed or till the protection circuit tripped out.
Perhaps it is easier to protect button-top cells by putting the protection circuit at the bottom.
Is there a list of which batteries are using top mounted protection circuits ?
Uh? Never seen one with PCB above the cell. Usually under the + cap (flat or button doesn't matter) there is the safety overpressure valve, which needs to open and bleed pressure outside in case of extreme overheating/overcharge. Notice on many cells the small holes around the + button.
Don't think they want to place a PCB to block the safety overpressure device...
Also, wraps don’t tend to get damaged in a torch, their damaged when you fit them……the protection circuit is not a reason to pass up on common sense. Sorry to sound harsh, but if a cell does not seem right, best bet is either make it right (new shrink wrap), or stop using it. I can’t see an issue with the protection circuit on the negative side, as said, it leaves the cell vents clear.
That would be because electrical charge really flows from - to + . Although every diagram you see says otherwise. There again thinking about it they do run the + part down the inside of the wrap.
I wonder if its possible to make a protection circuit that you just needed to add to the bottom of a cell and it took care of over discharge and to much ampage