special ed
2nd Lieutenant
- 5,591
- May 13, 2018
Smoking can kill.
Quotes and Jokes (2 Viewers)
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SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Close cover before striking.
MiTasol
1st Lieutenant
NiCad batteries had all sorts of thermal runaway (a discrete way to say often uncontrolled fire) problems 40 years ago but they are extremely reliable now.
The thing that gets me is people are putting these new batteries in aircraft and not using specially tested and certified aviation batteries (remember the early 787 battery problems and those were certified).
For those who have never seen a thermal runaway on one of the new electric car batteries watch this - and keep a close eye on the truck beside it.
IF this happened on an aircraft what chance do you think the pilot has of finding an emergency landing area and safely landing before things get out of control.
Thermal runaway can happen with any type of battery. I've had it while taxiing a PA-28, luckily I caught it before it became self-sustaining, but the fumes would have been incapacitating if I couldn't have opened the door.
MiTasol
1st Lieutenant
I bet there were more electric car fires in NZ last year than fires at petrol stations, and that they were more frightening. I saw one story, with photos, on an electric BMW that caught fire in a very narrow SI road and the people in it lost everything because it took them a couple of minutes to find a safe place to pull over after the "call your dealer" light came on. And it blocked the road both ways because the fire was so fierce.
MiTasol
1st Lieutenant
That one is purely an idiot operator problem - it is not built in to the car at the factory.
AND the idiot deliberately sprayed fuel over the car and set fire to the car.
That was on the Whangamoas. The road isn't that narrow, typical single-lane each way.
Honestly, I've see more burnt-out petrol vehicles on the side of the road, but no-one seems to think there's a problem there.
MiTasol
1st Lieutenant
Yes there are burnt out cars for other reasons but what percentage of the cars on NZ roads are electric and what percentage of the fires are electric?
There was a nice new diesel SUV burnt out beside the road near us last year. City slicker pulled over onto the long dry grass and kept his engine running while taking a phone call. The exhaust set the grass on fire which burnt through the plastic fuel line and hey presto. That is again idiot operator problem, not the cars fault. Our local firies also had to put out a long series of grass fires as well as a car fire because an idiot kept driving their car when the tire shredded and the wheel was destroyed and brake drum was sending sparks everywhere. It was all filmed by the car behind and made the news here. Again a @#$%^&*() moron behind the wheel problem. In this case he knew he had a flat tire and was driving to a servo to get it changed.
Not a built in at the factory problem.
and how long were the 'few minutes' that the previous car had been driving with the light on? When everything is burnt out, the only source of information is the same person who is asking the insurance company to pay out.
MiTasol
1st Lieutenant
True but that video shows how fast they can turn into an inferno.
ThomasP
Senior Master Sergeant
The older Ni-MH batteries are relatively safe from ignition as long they are not physically abused, and if the proper maintenance checks are done on multi-cell packs. As long as the battery cell is physically intact, it will not start on fire due to normal use. However, overcharging and short circuiting can cause the battery to get too hot, causing materials in contact with the battery to ignite (individual Ni-MH cells do not, in general, contain current limiting circuits). Also, the heat may cause the casing to fail, in which case a fire may be started when the negative electrode is exposed to air (the negative electrode is made of lanthanide series metals and is designed to absorb hydrogen ions, after which it becomes pyrophoric). A Ni-MH cell in and of itself - under normal use - does not explode.
This is not the case for the Li-ion types, as there is the chance of a failure of the internal/external regulator circuits, which can result in a "thermal event", ie a fire or in rare cases a low order explosion (kind of like a capacitor going off, but with a longer time of heat release). The regulator circuit in a Li-ion battery is designed to prevent the release of the stored energy at a rate beyond which the materials of the battery can survive, and to create a more stable level of energy output. In the same way, when a number of Li-ion batteries are arranged in series and/or parallel - to allow either increased voltage, or more amperage, or both - there are normally additional external circuits and sometimes other mechanisms incorporated designed to monitor/control the individual cells and the packs. In addition, if the battery cell or pack is short circuited, a failure of the monitoring/controlling circuits may occur - which may cause fires in the surrounding environment or cause a low order explosion of the battery.
In both types of battery, there is almost always a physical vent "valve" to reduce a build up of gas pressure in the batteries. This could be a sophisticated system for large cell packs - with electronic sensors and an actual valve mechanism - or just a gasket that fails at a certain psi such as in watch cells.
The above is a very general and simplified explanation.
This is not the case for the Li-ion types, as there is the chance of a failure of the internal/external regulator circuits, which can result in a "thermal event", ie a fire or in rare cases a low order explosion (kind of like a capacitor going off, but with a longer time of heat release). The regulator circuit in a Li-ion battery is designed to prevent the release of the stored energy at a rate beyond which the materials of the battery can survive, and to create a more stable level of energy output. In the same way, when a number of Li-ion batteries are arranged in series and/or parallel - to allow either increased voltage, or more amperage, or both - there are normally additional external circuits and sometimes other mechanisms incorporated designed to monitor/control the individual cells and the packs. In addition, if the battery cell or pack is short circuited, a failure of the monitoring/controlling circuits may occur - which may cause fires in the surrounding environment or cause a low order explosion of the battery.
In both types of battery, there is almost always a physical vent "valve" to reduce a build up of gas pressure in the batteries. This could be a sophisticated system for large cell packs - with electronic sensors and an actual valve mechanism - or just a gasket that fails at a certain psi such as in watch cells.
The above is a very general and simplified explanation.
Last edited:
special ed
2nd Lieutenant
- 5,591
- May 13, 2018
special ed
2nd Lieutenant
- 5,591
- May 13, 2018
Perhaps some military humor:
special ed
2nd Lieutenant
- 5,591
- May 13, 2018
Maybe another:
Prop Duster
Airman
Greg Boeser
1st Sergeant
Back in the day, when people could still smoke in restaurants, flipping the ashtray over converted that table from a "smoking" table to a "non-smoking" table.
If you were lucky, the ashtray would be empty before they flipped it.
If you were lucky, the ashtray would be empty before they flipped it.
ARTESH
Chief Master Sergeant
All of them are imposters ... All of those lands belong to us!
We have to restore the mighty Achaemenid Empire ...
Achaemenid Empire - Wikipedia
special ed
2nd Lieutenant
- 5,591
- May 13, 2018
special ed
2nd Lieutenant
- 5,591
- May 13, 2018
