This may sound like a dopey question to you, but are you able to tell if an 18650 cell has pcb protection just by looking at it, ie; does it have some distinguishing physical feature over a non-protected cell ? A good quality cell will have a brand name, MAh rating and protection status ( eg; AW18650 [ this is a random pick only ! ] ). I recently disassembled an established manafacturer's cordless drill Li-Ion battery, with a faulty cell. Inside was 10 x 18650's all spot welded together with fine metal strips. The cells were shrinkwrapped in waterclear green wrap with absolutely no marks on either the wrap, or the metal body of the cell to indicate anything. + and - were easy enough, and a DMM found the faulty cell, but other than that, what would show the cell to be protected, if at all ??