This thread has gone thermal runaway.
LI batteries are as proven, and maybe more, than any other battery technology, ever. Does your Iphone or laptop have a placard that says "charge only 5 meters from a flammable object, and never indoors?" How about your Makita LI powered drill?
How many of us have had a Iphone or laptop battery ignite?
Every aircraft that takes off and lands has a couple of hundred LI batteries in the passengers luggage. These batteries are not aircraft rated. They are the cheapest pieces of crap that any company could source, charged by the cheapest piece of crap charger that can be sourced. In Asia you can by a charger for less than 2 dollars, and a 2100 mah battery for 7 dollars. I have 4 in my bag right now. I have carried them on hundreds of flights, and the aircraft did not self-immolate.
A 787 sized aircraft carries 20,000 gallons of combustible jet fuel. Bigger aircraft much more. All jets other than a 787 have pneumatic pipes that carry engine bleed air at 100-700 degrees C, all over the aircraft. In effect, these pipes are carrying fire all over the aircraft.
What we are talking about is two little cubes of electrical charge. A couple cubic feet each, and 70 lbs. The only time it went completely nuclear, the thermal damage was contained.
If I were to put my own money on the line, I would bet Yuasu makes the finest lithium batteries on the face of the earth. Thales designed a box that contained the thermal damage. Somewhere there is a single fault that caused these problems. It will be found, and fixed.
My guess? Possibly 2 defective chargers from Securaplane. Or a specific set of aircraft equipment, operated very occasionally together, that put noise/AC/spikes into the aircraft grounding system, and that affected the charging.
Going away from LI? OK, lets just go back to land line phones, desktop computers, etc. Typewriters and sliderules?
LI is proven. It is safe. It is not perfect, and it has its limitations.
If you want to eliminate fire hazard on an aircraft, maybe it is better we stop carrying jet fuel? 747's probably carry 50,000 gallons of it. And a few feet away is high temperature engine bleed air, coursing through pipes, in a wing swinging up and down several feet, during turbulence.
This battery problem, in the end, will be a zit on a bug's arse. It is nothing compared to the engineering that has made commercial aviation, consumer electronics, automobiles, etc, SAFE.
A hundred post ago this thread was great. It is now turning into......PPRUNE.