An external battery pack for protecting against a battery fire or battery explosion, said battery pack connectable to an emergency locator transmitter (ELT) typically mounted in an aircraft. The external replaceable battery pack has a protective metal enclosure and a removable metal cover. The box includes an aluminum honeycomb grid core mesh with passages, each sized to receive a single battery and a pair of printed circuit boards on top and bottom to receive battery power, voltage and current, from multiple batteries for use with an ELT. By using smaller and more batteries together, the possibility of a catastrophic failure is greatly eliminated or reduced in that a smaller battery have a lesser fire or explosion potential. The batteries are isolated from each other from excessive heat or destruction by explosion.