Belgian1979 wrote: Hairyscreech wrote: GARY C wrote:
Lets hope this doesn't happen to the elec cars.
Japanese firm announced on Thursday that it would recall nearly 1.2 million Accord vehicles produced between 2013 and 2016, after receiving multiple reports of the cars' battery sensors causing fires in the engine.
http://money.cnn.com/2017/07/14/news/co ... index.html
There does seem to be a bit of a trend with electric cars and fireballs after accidents, Richard Hammond was nearly in one recently and there was a guy not long back who's Testla the fire brigade could not put out, questions on that one if he was dead before the fire started or if he was just unconscious and they had to let him burn...
It has to be said that fuelled cars are not exactly hazardous free either. However, the fire brigades are not yet equipped or trained well to deal with a car with Li-ion batteries that catch fire. Water is like pouring oil on fire in that case.
No arguments there, anything carrying a combustible liquid is going to be fire risk, ask anyone that knows old BMWs, the fuel hoses perish and leak onto the engine block! Never personally seen one go up from that issue though, seen one leaking to the point that there was actually liquid fuel visible on the side of the block, car stank of fuel.
Even when leaking quite badly normal gasoline is still reasonably hard to ignite and needs a decent source of ignition, the 100+ degrees of the engine block is not enough on it's own, only really vaporising the fuel.
We were curious about the movie trope of throwing a fag but into a pool of fuel to light it once so were actually trying it with a metal bucket and a couple of litres of fuel (yeah I know, dumb, just don't
) but we could not get it to go up. Even pouring some out to get more vapour it was still not quite enough.
I will say my personal experience has been that oil and the electrics have been a greater fire risk than the fuel, seen a few cars burst into flames after putting a rod through the block or loosing a turbo oil feed, hardly surprising there though.
More worrying seems to be VW vans with sticking starter motor solenoids, heat just builds up while they are parked until the loom catches fire.
Totally agree about the the fire services being ill equipped to deal with a Li-ion or Li-po fire, in the big arrays used for an electric vehicle, there's a serious amount of power stored in them and unlike a fuel leak it can light itself. A shorted Li-Po cell is a real threat, seen a lot of R/C models go up from that and a lot of the R/C guys charge their batteries outside in a metal tin.
When a bank of cells gets crushed it's pretty hard to know what it is going to do, if you approach a crashed EV how do you asses the risk, is the body live? Are the cells about to cook off? Check out NASA's recent robosimian detonation for a good example. https://www.youtube.com/watch?v=UxJBRK2EXFc
Manufacturers do design in fail safes but they cannot be relied on, I am put in mind of the nuclear missile issue where it was proven the heat of a fire could melt the solder on the circuits and potentially detonate the warhead.
I can't see lithium based batteries really being a long term solution for electric vehicles, there are too many challenges around them. Production is expensive and messy, we can't recycle them, failure modes are not too clever, we can't put them out, they can't easily be changed, the list goes on.
The fluid/flow batteries seem like a much better solution, while they will have a lower energy density this is solved by the possibility of exchanging electrolyte quickly and easily for ready charged electrolyte and a damaged cell will leak out and become no more dangerous than a dry lead acid battery or if the flow of electrolyte is prevented then there is only the charge in the cell at that moment to be dealt with, also depending on the electrolytes used the fire risk is much lower.