Fuse...
It increases resistance as the current goes up to protect against overcurrent and resets itself when the conditions allow. You can reuse it or get other one from DigiKey...
# SRP420-ND
http://dkc3.digikey.com/PDF/T041/1130.pdf
You might find this useful. I posted full instructions for rebuilding batteries here...
http://forums.mtbr.com/showthread.php?t=52685
It increases resistance as the current goes up to protect against overcurrent and resets itself when the conditions allow. You can reuse it or get other one from DigiKey...
# SRP420-ND
http://dkc3.digikey.com/PDF/T041/1130.pdf
You might find this useful. I posted full instructions for rebuilding batteries here...
http://forums.mtbr.com/showthread.php?t=52685