Originally Posted by G0ULI
"Banning what many passengers regard as essential consumer devices for business or holiday use would be pointless....Given the ease with which equipment can be counterfeited and manufactured from substandard components, I must reluctantly concede that a ban may be the only way workable way "
These are both good points and illustrate the inherent conflict. Banning all li-ion powered consumer devices would mean no cell phones, no portable music players, no laptops, no tablets, no Kindles, no cameras, etc.
You can't validate these at the airport since many of the batteries are internal, and cut-rate external batteries look just like the OEM versions.
The only li-ion device I have had go into thermal runaway was a Logitech Harmony One TV remote, which had the OEM battery in it. Without warning it started smoking and become so hot I couldn't hold it. The LCD was melted and discolored and so was the plastic chassis. It was never dropped, mistreated or modified in any way. The battery was tiny relative an an 18650 -- I'd hate to see one of those experience the same failure mode.
From an individual standpoint, you can always use high quality OEM batteries and chargers but even that is no guarantee and it seems impossible to enforce.
There is no good answer for this situation.