A Lear Jet caught fire when a battery overheated and burned a hole in the
fuselage. This was caused because the new battery had such a tremendous
current capacity. No, it was not a lithium ion, it was a nicad. That was
about 35 years ago and the FAA issued cautions about the problems created by
nicad batteries.

I have also read about people being seriously burned when the nicad
batteries they were carrying in their pocket shorted out on their keys,
burning a hole in their pants and in one case leaving an imprint on the
thigh of the victim.

Any device that stores or creates energy is a potential hazard. What is
required is that the user understand the potential hazards and minimize the
risks.

We drive around in cars full of gasoline, which may burn or explode in an
accident, on tires that may suddenly deflate because of an object striking
them. And, we are 4 feet away from a vehicle coming the opposite direction
going 50 miles per hour. Sometimes where we draw the line between what is
safe and what is not is rather arbitrary.

Colin