.... that they like the batteries tied together so I always use a rubber band and make sure they can't touch end to end.
Don't ask me why...it makes no sense to me, but that's what happened.
There must be something about loose batteries....
It might not make any sense,
but you guessed "the why" exactly.
Leaving them in dive lights is a really horribly bad idea. This is part of what they are
programmed to look for. Dive lights that get turned on have made their hot list (not to make a pun), so when the rules are given to the security folks, it gets put into the least common denominator:
No batteries in flashlights.
Unfortunately,
in the translation (from the original English version FAA/TSA advisory) this gets messed up and is sometimes interpreted to mean photo strobes.
You can easily incapacitate the device all loaded with batteries by covering the battery contacts with duct tape before sealing up the light, etc.
Another English language origination FAA/TSA advisory spawned from the commercial air transportation ban against
bulk pack Lithium Cells. As these batteries have become more and more available in the sizes used by us common folk, TSA types have had to been re-educated as to allowable methods for Lithium batteries. Here, though, is a prime example of a flashlight you do not want to get turned on mid-flight. A consumer level available law enforcement flashlight such as a Surefire brand can easily ignite wood, plastic and surely clothing.
I have seen two occasions where dive bags were being handled and were emitting smoke. Both were after they had been picked up by the passenger and they were heading toward the dive-op.
The first major airline security confusion came from the ban on certain types of batteries that were commonly found in power-wheel chairs. This caused all sorts of nuttiness on the passenger interface level.
If you want a real headache, try to decode the requirement for transporting ammunition. After that, checking a gun through will seem easy.
I heard that electric toothbush story in regards to a slightly different type of personal device
Ahh, for the old days. When the FA's were called Stews, they wore
hotpants, and you just handed your gun to the Captain as you boarded the plane.