787 Battery Tests
This extract from a Boeing video shows a severe test of the proposed 787 battery containment enclosure. Propane gas ignited inside the box explodes. The 1/8th-inch thick steel walls bulge out but hold fast.
So if a box of that size filled with a propane-air mixture holds the same energy than a fully charged battery, then maybe the idea of the cartridge APU starter was no too far off, we just have to route the overborad vent line to the APU, and voilį we have the perfect APU start energy source. A propane-in-a-box cartridge starter. Probably not 16k$ each as well...
Seriously, which percentage of the energy stored in a fully charged battery has been released in this test? My rough estimation is about 2% (Propane having 28.2 kWH/m³, Battery having 75Ah at 29.6V with a size of 15x11x9 in... according to NTSB)
"Over a hundred people have died in less than 100 years, which gives a 1:100 years failure rate. In the first 10 years of life that is a 1:10 chance of dying."
So taking into account that a birth takes in average 2 hrs, there is a 1 in 438000 chance to die during birth... Which is a quite optimistic number.
Statistical fugures do only work, if you look at a large enough population/timeframe. So the estimation over 500 aircraft and one year was probably much more realistic than a chance of death during a fraction of the MTBF...