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But the car batteries and cables need active cooling to soak up the 450kW safely.
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But the car batteries and cables need active cooling to soak up the 450kW safely.
This could very well change the electric car game.
I'd imagine it will fall down to how much these cost to implement along with how they'll affect battery lifetime.
You think?Quote:
But the car batteries and cables need active cooling to soak up the 450kW safely.
Fast charging is great, but certainly in the UK there needs to be some sort of work to standardise chargers, how you pay for them etc.
Well, the UK could use these Combined Charging System chargers, and give the power away for free, just like this scheme.
Tesla will in the future support CCS as well apparently.
WOW! if something goes wrong the lithium batteries explode taking a few blocks in the street.
Great idea. The current problem is getting the same power that can power 150 homes to each charging space. A motorway service station with several spaces will need it's own substation and high voltage supply I guess.
Battery lifetime: 6 charges. Just what the manufacturers would like....
Thats nothing, in a year or so it will be :
https://www.youtube.com/watch?v=p46VOwNUOdw
It's BMW too....& so long as the BMW has star marked tyres, it should be well protected...but if you fitted non approved tyres... well... puppies will die at the very least.
Hows this affect the life of the batteys? does it shorten them any compared with standard charging?
Generally it's the heating and cooling that'll cause problems and rapid "ageing" of the battery. The more intense the heating, the faster the individuial little itty bitty cells short out, removing their capacity from the overall effort (this is what has been explained to me by people who proport to know so if I'm wrong, please someone correct me). I suspect if active cooling is required, that's probably at the moment purely to keep the battery within safe operating conditions. Endurance is another matter and something they'll be analysing very carefully under an electron microscope when they autopsy some batteries that have been through this. Interestingly, Prius batteries from the very first ones are showing surprisingly little degredation.Quote:
Originally Posted by Platinum
I remember a couple of decades ago, we used to say one fast charge for every two slow charges for "performance" batteries back then but I think that (considering we were talking about lead acid batteries) that was due to accumulation of sulphates on the electrodes which were removed by the slow charger, so a different method of failure. The point being that they may (certainly initially) say you can only do so many fast charges before you void your warranty.
There's also the issue of power factor when you're looking at all of this. Even standard fast chargers run at the limit of your grid's connection (now they have changed from KW to KVA with smart meters, gits). You have a few of these running and on the face of it the grid load will be huge, never mind if it's a huge inductive load meaning the grid has to provide a good whack more energy than is being used.
Personally, when looking at the mobile phone as a use case, I have it slow charge wirelessly overnight which takes a good few hours but I also keep a fast cable charger by the bed as well to allow me both options. I'd certainly not put any battery that I wanted to last as long as possible through rapid charging. There is a sweet spot charging rate at which you can shove in pixies before it starts to significantly impact battery life - I think most fast chargerse for phones work on this (although this sweet spot changes as the battery charge increases so the charge rate drops over time).
Lithium batteries don't 'explode' in the conventional sense, they burn rapidly when they're badly damaged. However more modern cells are far more tolerant of electrical neglect and manufacturers frequently include the results of such tests in their datasheets. Large packs like this have carefully-designed charging and BMS systems which will stop charging if anything goes awry.Quote:
Originally Posted by lumireleon
I don't expect they'd install say a service station with enough capacity to simultaneously provide maximum power to each charging station. The supply would most likely be provisioned based on average demand of some sort.Quote:
Originally Posted by badass
I remember reading a paper fairly recently showing the wear caused by fast charging is less than often claimed. Also, this article doesn't state anywhere that that's a full charge in 6 minutes, or anything close to it. It could be something like a 25% charge which wouldn't be far off the 30 minute 'fast charge' commonly specified for this sort of battery anyway. One of the most time consuming bits of charging li-ion batteries is the current taper (CV stage) after the 'fast' part at full current, and IIRC some car manufacturers deliberately leave this part off anyway (or only do it as an option if you're planning to drive a longer distance) to maintain the batteries at a lower SoC with the aim of improving cycle life.Quote:
Originally Posted by gagaga
Not around here they haven't - sure they can measure kVAh but domestic customers are still billed for kWh.Quote:
Originally Posted by philehidiot
I'd be quite surprised if these charging circuits didn't have some decent form of power factor correction given even things like phone chargers have mandated minimum power factors in many countries now.Quote:
Originally Posted by philehidiot
Agree with the rest though - while there's some truth in many of the concerns, I think some are overblown and repeated as gospel with little evidence to back it up. As a bit of an anecdote, I fairly recently dug out and tested some 18650 cells I've had lying around for close to 10 years and only cycled maybe a dozen or so times. Upon measuring internal resistance and capacity, I was pleasantly surprised to find they're nearly all right on original manufacturer's spec! And some of them have even been stored at fairly high SoC too. One of the ones which seems to have lost a bit more capacity than the rest is an older Chinese-made one and not from one of the big 18650 manufacturers, and has been cycled a fair bit more than the rest.
It hasn't happened here because I keep saying sod off to a smart meter.... If you examine your bill, you may find that they've changed the connection limit. On consumer units there's a breaker for 9KW and now they've changed the connection limit on the bill from 9KW to 9KVA (who's gonna notice?) and there's a breaker in the smart meter which will fire off before the consumer unit one which is set to 9KVA, which is obviously less than the 9KW (although the mathematician in me hates these mathematically identical terms being used for different meanings, damn engineers). Why have they done this? Well, so they can begin to take into account power factor for consumers but also you'll note that a (I think it's Tesla) fast charger for domestic EV use is rated at.... 7KVA. Handy that. Just to ensure you need to pay more for your grid connection. Very agreeable.Quote:
Originally Posted by watercooled
I'm sure you're right that there will be the usual switchable banks of capacitors to correct the power factor but my understanding is you can't completely merge the out of phase V and I sine waves? Just out of interest, what happens if you're out of phase by 90 degrees (and so the cosine of theta between voltage and current = 0?). Does that mean there's zero output?
Watts are volts x amps. A KVA == KW, it's the same unit...
VA and W are not the same thing - in AC systems, VA is a measure of apparent power, which is the vector sum of real power and reactive power (i.e. reactive elements - inductive/capacitive). W is a measure of real power only. The difference between the two is expressed as cos phi, the power factor, a ratio derived from the angle between the two values.
Circuit breakers and fuses are rated in Amperes, not watts. For a domestic supply, the main fuse is typically 100A which supplies a consumer unit which does have a main switch then usually the next overcurrent device will be the MCB or in some cases an RCBO which is specified for the individual circuit, not the installation as a whole which is protected by that fuse in the cutout, and maintained by the DNO.
If 9kVA were converted into current, on a 230V supply that would be just ~39A, maybe the sort of thing you'd see for a large circuit e.g. 40A MCB for a shower, but again not a whole installation.
The 'connection limit' or maximum demand, has always been expressed in either kVA or Amperes, because kVA is more relevant than kW when sizing conductors, protective devices, etc. It's nothing to do with being ripped off.
If you're out of phase by 90 degrees, yes you pass zero useful power and have a purely reactive load. Obviously that's not going to happen on a real circuit as there will still be a resistive element but that's how the maths works. The cosine of 90 = 0, hence the power factor is zero. At the opposite end of the scale, the cosine of zero (I and V in phase), you have a power factor of 1.
Edit: WRT power factor correction, there's more to it than just throwing capacitors at it, and it really depends on what the load is like in the first place. For a sinusoidal inductive load e.g. motors, capacitor banks can work well, but there are many other methods. On some loads like with switch mode power supplies you generally also end up with non-sinusoidal current as well as it having a reactive component - look up active power factor correction as an example of how it corrects the current waveform.
They are in terms of the basic maths but in the practical application of electronics they are used differently and there are different ways of calculating them. This is one of the reasons why changing from W to KVA on your connection spec is very sneeky. Everyone who notices who isn't inducted into the devious, dark, evil realms of electrical engineering will do exactly what you did... "hmm, that's different. But W = volts x amps and therefore it's the same, they're just expressing it differently".Quote:
Originally Posted by Tabbykatze
Cos phi(l is an idiot).Quote:
Originally Posted by watercooled
Why did I have theta in my head? Doppler probably.
Obviously, I was being slight blase when I was going on about a bunch of capacitors however, in the typical inductive load environment like industry when you've got loads of motors spinning up and down, I can see the load varying in a fixed range but by an infinite number of increments. If you've got what amounts to a giant transformer and say three pixie pumps attached, I would expect power factor erection to be pretty straight forward as the number of different loads will be fixed and (whilst there will be some issues like temperature and quite what rate it uses to charge the battery) therefore you can establish and pre-program optimum correction for any of a limited number of situations as pretty much all the variables are known?
I'm just not too familiar with these high power charging systems yet so I'm not sure what sort of PFC would be appropriate, is all I meant, I didn't mean it to come across as dismissing capacitor banks as a method of PFC - as you say that method is commonly used for inductive loads such as motors or discharge lighting which often have caps integrated for this purpose.
If it's an AC supply to the vehicle, then the PFC would be determined by how the vehicle's own charging circuitry works, but if it's a DC supply then it would be up to the charging station. I'm not sure how that DC supply is provided but I imagine it's more than simple rectification and smoothing as that could lead to pretty poor PF caused by non-sinusoidal load. It's something I'll look into though!
I always assumed that the Tesla powerwall units came from using a storage battery in their supercharger setups to smooth demand to the grid? Pictures of chargers in the US seem to have solar panels nearby which I'm sure I read charge local storage.
Not sure what the state of supercapacitor technology is atm, not a component I ever use. I would have thought mains supply to supercapacitor, then when a vehicle turns up it can charge on what is stored in the supercap would be the ideal way. It only needs to provide power during the fast charge phase.
As for smart meters, I was taught in my engineering degree that domestic properties were good enough power factor that it wasn't considered worth policing by the power companies.
It's not a game changer. It *could* be, but the caveats are easily big enough to knacker it.Quote:
Originally Posted by eHM
It'll cost a packet to implement these in any number. 450kW per outlet. If you're trying to design something analogous to a motorway service station, with 15, 20 of them - and the potential for all to be in use at once, your service area needs a 6-9 megawatt supply. That's going to be the fundamental sticking point I'd suggest.
Then you've got the need for active cooling of the battery pack, plus, as you say, the potential risks of the battery failing and/or its working life being materially reduced by such aggressive charging.
Right now it's a proof of concept - and the other thing I want to know about this is the headline '100km' figure. That's an estimate - the actual technology is merely trying to get a certain amount of megajoules of energy into the battery. So is the "100km" figure an optimistic estimate based on a brand new battery with 100% health and unrealistically economical driving cycle, or...?
EV battery packs tend to have active cooling/heating systems anyway, so that part's likely a non-issue. I don't think the electricity supply or battery issues are as big of a deal as people are assuming either.
@DanceswithUnix: That could well be how they work, and it makes a lot of sense especially when they have the 'superchargers' combined with overhead solar panel canopies.
I did a bit of reading last night and it looks like at least some of the DC chargers are fed by SMPS: http://epsma.org/HP%20SMPS%20Applica...May%202017.pdf
That's exactly what I was told so when I heard about it, I tried to think why and it does make sense to some degree. Think about the high inductive load stuff like the pump in your power shower, the washing machine, dishwasher, etc. Whilst not new, new, they are going to ensure the power factor of a specific home is not what it was in the days of hand washing and those weird washing machines which just sort of mashed. Whilst yes, it has been a long time coming looking at power factor in domestic supplies, they probably though that if they were redoing all the meters anyway then why not? Bearing in mind they aren't replacing everyone's meter "for free" out of the goodness of their hearts and will look to turn a profit from as many ways as possible. I think it's just something they now have the opportunity to do and is now worth doing given the increase in inductive loads in a domestic property over time.Quote:
Originally Posted by DanceswithUnix
As for the Tesla things charging a battery over time to smooth demand, they may do but it woudn't be efficient. Charging a battery from a solar array makes sense but you get decent charging and discharging losses when you do that so it'd probably be worse for the home owner than just charging the car directly. Also, the best time for the grid will be over night which is when most people will charge an EV anyway. The 7KVA charging I seem to think is Tesla but I may be wrong and it may be a different company and so you may well be correct. The system I've got in my head will charge a given car (it would be nice if I could remember that part and I could figure out the brand!) in 3-4 hours from dead whereas a standard domestic supply will do the same car in ~12 hours. Gonna guess one is 3 phase. Obviously most people won't be coming back with a dead car but if I was doing it I'd definitely not be doing it without the fast charger installed.
At the moment, Tesla battery technology is apparently a load of Panamasonic 18650s strapped together. I've never seen this but if it's true that absolutely hilarious. Reminds me of wiring together a load of 9V PP3s when I was a kid.... I can see the practical benefits in terms of management of the battery but still.... that's a whole load of cells! I bet their amazing new factory will come online JUST as a breakthrough in supercapacitor tech comes along which makes it cheap and perfect for EVs.
As to whether it's the car or the station - domestically I don't know. However that photo shows something suspiciously like a giant transformer in the background. With high input I'd expect the car would also have enough cooling to deal with and making as much of the conversion gubbins external as possible would allow for far better active cooling.
The EV packs may have active cooling but in a confined space are you going to be able to remove enough heat to ensure the temperature increase is not affecting endurance? Bearing in mind the vehicle will be warm at the services, not cold to start with.
As for the grid coping - round here no chance. During winter they have to attach back up generators to my local substation as they can't deal with current demand. The margins for electricity production in the UK are utterly tiny. Once we get storage of renewable energy sorted (some great stuff with cryogenics which might well work coming along last time I checked) then we'll have a way better chance. At the moment we're in an energy crisis which is why they've accepted such a horrific price and the Chinese being on board for new nuclear. The big coal generators being closed down didn't help. This is entirely our own politician's fault as none of them had the balls to commission anything before we got to crisis point.
Austrialian engineer's point of view on this:
https://www.youtube.com/watch?v=w_OYbZzWk5E&t=0s
Domestic premises in the UK are billed for kW, not kVA. The meters are capable of reading kVA, in fact it's simpler to do so and even older 'non-smart' meters were capable of doing so, but they're not configured that way.
Charging li-ion batteries is reasonably efficient, and you have to weigh that loss against transmission losses in the grid - I doubt there's much in the difference overall.
There's obviously a difference between on-demand 'fast chargers' used to top up at a service station and conventional, routine charging - the latter can be configured to charge during off-peak hours by default, and there's even talk of using EV's connected to a grid as a form of balancing during peak demand, which would help level the characteristically peaky nature of the UK's electricity grid.
Most if not all EVs on the market, Tesla included, use packs of cylindrical cells such as 18650 though IIRC Tesla are moving towards 21700 cells for better energy density, it's just a sensible (practical and economical) way of constructing and maintaining battery packs.
While supercapacitors have excellent power density, they're about two orders of magnitude off li-ion batteries in terms of energy density. They might be useful alongside batteries e.g. for handling spikes in power/regeneration above what the battery can supply or absorb, respectively, but not as a replacement given current technology.
The cooling system will be engineered to handle the extra heat of rapid charging from the start, and it wouldn't be rocket science to, for example, supply a coolant circuit in the same lead as the power to circulate around the battery pack and charge circuitry (or through a heat exchanger) if the cooling requirements exceeded the car's own capabilities. I don't know how much they're capable of dissipating as-is, but if the cooling requirements for this system were greater, it would make sense to offload it to the charger rather than carrying around an over-specified cooling system which is only needed when stationary.
Betcha we are going to see a rash of bad batteries because of this. We already know that charging batteries too fast affects their capacity and lifetime significantly. Using a wireless charger on your cell phone will all but destroy the battery in a year of use due to the heat created.
I wonder how these guys are taking care of those issues; cell degradation and heat.
"What would happen if we all switched to electric cars". The same as if we all switched to diesel, the system wouldn't cope. Pointless thought experiment for an impossible scenario. I thought he was a salesman anyway, not an engineer.Quote:
Originally Posted by philehidiot
Ummm .... forgive me for being picky, and a bit late but it's 9pm Christmas day, so naturally the TV is cr.... rubbish.Quote:
Originally Posted by watercooled
But isn't the difference between "burn" and "explode" basically just rate of burn? i.e. rate of release of energy. Start a sheet of paper burning with the sun and a magnifying glass and it's a pretty slow burn. Strike a match and it's much faster. Short a lithium cell (especially a big one) and it's pretty fast for 'burning'. Do it in an enclosed space and .... ;)
What's the functional difference between a relatively slow "explosive", like dynamite, and a fast one like modern military explosives? Surely, speed of the 'burn'. Rate of change of the reaction?
Sorry I know it's off-topic, but I've always understood an explosive to just be something that burns comparatively fast, fast enough to create a pressure wave in the process, and the faster the reaction, the bigger the bang.
I've addressed this already - read the rest of the thread. Nowhere does it even say this is a full charge in that time. And do we really 'know' this? And who is 'we'? Lots of these claims are simply hearsay and with little supporting evidence, or perhaps from early cells. Heat does seem to degrade cells faster, but I'm yet to see any conclusive evidence that fast charging within specifications significantly impacts life. Heat is one they have specifically spoken about in the article though, go read it.Quote:
Originally Posted by DaMoot
I was being somewhat pedantic but there is a difference between an explosion and burning. Any properly designed lithium cell will have safety mechanisms so that, in the event of catastrophic failure, safety vents open and the hot gasses escape, sometimes fairly rapidly. They should not 'explode', as in a violent disassembly sending shrapnel flying. If you were to contain the cell in something like a hermetically sealed case with no proper safety vents then yes you could make *that* explode, but I highly doubt the engineers behind automotive battery systems would overlook something as fundamental as that. And by the same logic, if something like a pressure cooker had no safety valves and it failed then that could also explode, but you wouldn't go around saying 'water explodes'. Remember the hot water cylinder with blocked safety valves from Mythbusters? :PQuote:
Originally Posted by Saracen999
Having said all that, the difference is a fairly important one, some smoke and hot gasses escaping a few feet away from you might be cause for alarm and probably evacuating the area, particularly if it's indoors or in an enclosed space, but it's considerably less severe than something actually exploding right next to you, sending bits flying which could cause injury for some distance. And that's the whole point in including pressure relief valves in batteries along with lots of other things which contain pressure - a controlled release of the contents is usually better than an uncontrolled failure of the vessel.
One example I could find with a deliberately pierced battery (and one of the more extreme that I've seen): https://youtu.be/WnZuMfq6kec?t=2m18s
But even that's a pretty extreme example - if you check out some 18650 datasheets the manufacturers often report on results of things like overcharging, short circuit, etc. Check page 6 of this pdf (page 5 as printed): http://dalincom.ru/datasheet/SAMSUNG%20INR18650-25R.pdf
Edit: Another example where two cells are shorted - there are plenty more on Youtube if you search. https://www.youtube.com/watch?v=rDSqhmSGwVY
The insides of a car are pretty combustible (ask Ford) and so the problem in my book would be not the battery going pop (as you say, they're designed to fail relatively safely, if dramatically) but the heat causing a secondary fire in the cabin and the gas also getting in there. Both things I think could easily be designed around and I would be amazed if they were overlooked. I think the main issues with this kind of fire is getting the damned thing to go out as it tends to chain react over a long period of time and throwing water on it.... doesn't seem to help that much for some reason. I've heard reports of fires going on for a couplpe of days and so I'd expect new firefighting techniques may be required.
We do have to put things in perspective though, e.g. the comparison is against carrying around 50 litres of petrol.
I would imagine the battery to be stored external to the cabin and insulated from it to reduce the spread of fire and smoke, constructed and installed in a way to protect against direct impacts, and to have some sort of cut-out to prevent shorts, like how cars can have fuel cut-outs linked to airbag deployment/crash sensing now.
@watercooled ...
Ignore, if you will, pressure cookers, etc. That is not an explosion in the sense (and definition) being discussed (by me, at least) as suggested by the word "burn" Yes, there are various dictionary definitions of explosion, from "an explosion of emotion", to a population explosion, to debunking a myth by "explding" it, but the form I'm talking about is that generally referred to as involving "explosives", and there, paraphrasing, we are talking about a material storing a significant amount of potential energy which, if initiated, typically resulfs in the release of light, heat, often sound and usually expanding gases in the form of a pressure wave.
So, having done some Goog .... erm, DuckDuckGo-ing, I came up with something like this.
When a material storing such potential energy is "initiated", a combustion process starts. At the very slow end, we call it "burning". But generally, the combustion process whilst representing a broad spectrum of combustion speeds, can be categorised as "deflagration" or "detonation".
Deflagration is where the pressure wave front moves through the gases at a speed less than that of sound, while "detonation" is where the pressure wave moves through the material faster than the speed of sound.
In both cases, the speed of sound is "in the material", not in air, and will be different from the normal "air" speed.
So when I said the difference between burn and explode is the rste of burn, perhaps a more accurate term would be rste rate of reaction, or the rate at whuch that energy is released. It's a continuous spectrum of rate, with simple combustion (burn) at one end, up throygh deflagration (with, I suspect, a lithium cell letting go being up at the higher end of deflagration but lower than detonation, and then moving into detonation.
But even within detonation, it's a spectrum, and for instance, the difference between low explosive and high explosive is the rate of energy release once initiated.
Of course, there are other differences in characteristics, such as what is necessary to initiate the explosion. Some are extremely unstable (nitroglycerin) where dropping it might be enough. Others might require a shock wave go initiate. Hitting some with a hammer will do it (not recommended for personal experimentation) while others, particulary the really high explosives, require a substantial and fast input of energy, in the form of a suitable detonator, and you could whack away at them all day with a hammer and all you'd achieve is a very squished form of ultra-high explosive and severe muscle strain.
Anyway, the point, my original point, was that when you have a substance storing such pitential energy in chemical form, "burn" and "explode" are the same process but the latter, inherent in the nature of the substance, happens a LOT faster than the former.
This is the (relatively) simple chemical process involving the release of that PE, and is separate from putting vents in cases, etc. That is about pressure buildup in the case and the concern is much as it is with a pressure cooker with a faulty of hammed release valve, but is distinct from the combustion (deflagration/detonation) process of the explosive material itself.
You'll have to excuse me if I'm not doing a good job of explaining this. It's not my area of expertise, but I had it explained to me getting on for 40 years ago, by a manufacturer of high explosives, and then demonstrated for me in a test rig. You'd be astonished at what chartered accountancy sometimes involves, and this was part of an audit. A similar experience was a demonstration (different company) of the ability of "bullet-proof" glass to withstand a blast from a shotgun, or even repeated rounds from an assault rifle. Of course, the latter was rather thick. Similarly interesting was the process of making that BP glass i tne first place, which was more or less the same as laminated car windscreens with more layers .... and they were a bit coy about the exact laminate material. Even a dull old audit can have it's fun moments.
Anyway, now I'm digressing from my original digression. :)
Explosion != Detonation
A steam explosion is still an explosion, and an explosion does not need to involve combustion. I originally included some references to detonation but removed it to avoid confusion.
I said explosion in my original post and distinguished it from burning, all of those points stand. At no point did I or the post I was replying to say detonation.
Functioning correctly, batteries vent, not explode and certainly not detonate.
You're mixing terms when it comes to explosives but I'm not sure it's relevant to this topic, or this forum to be honest. Just one hint though, sensitivity is a separate characteristic altogether. PeriodicVideos on YouTube have some good videos on the subject.
Venting batteries are not exploding in the same way a struck match is not exploding. Let's not overcomplicate it.
Venting batteries prevents pressure explosions by venting pressure.buildup. That is not combustion, or what I'm talking about. Lithium batteries "burn" because of either electrical short, or physical intrusion causing electrical short, resulting in chemical combustion. i.e. burn.Quote:
Originally Posted by watercooled
Strip a lithium battery down to core cells, no hard case at all to cause a pressure build-up, and then puncture the insulating layer between the chemical layers and the chemical reaction causes heat, then jeat build-up, then a burn, which which I mean something from several inches to several feet of flame shooting out of it.
This is not a slow burn like, oh, setting fire to brandy on a christmas pud, but more like a roman candle firework, and once started, is next to impossible to extinguish, until the potential energy is released.
Functioning correctly, batteries don't explode. Agreed. But when not functioning correctly, lithium batteries burn pretty fast, and very agreesively. I don't need to watch videos for this, gaving seen it happen in person.
And as I said, the difference between fast burn, or fast combustion, and "explosion" of the type of chemical burn luthium batteries do, is rate of reaction.
I did not say lithium batteries explode. I said the difference between "burn" and "explode" is rate of the chemical reaction. And it is. And is nothing to do with venting. I'm not mixing terms, but you seem to think I'm saying something I'm not.
To be clear, forget lithium cells for a moment. When you have a store of potential energy, and it is released in an uncontrolled fashion, the difference between burn and explode is rate of reaction, rate of release of that energy. It's the same process, one slower, one faster. That, and that alone, was my point, and nothing to do with pressure cooker "explosions".
I have an ICE car with a "Lithium" 12V battery. From some of the comments here I would assume I am as good as dead :)
What I don't get though; do people really think that EV design engineers are unaware that they are storing large quantities of energy and do their very best to avoid, detect, contain and limit problems? I have yet to see anything like the EV equivalent of the Trabant were the petrol tank is gravity fed from above the hot engine!
Think what you want, you have made multiple statements which are factually incorrect. You are confusing explosion with detonation. An explosion absolutely does not need to be a chemical reaction. But I'm bored and it's way off topic. My original statement was correct so the digression is pointless.Quote:
Originally Posted by Saracen999
Quote:
explosion
/ɪkˈspləʊʒ(ə)n,ɛkˈspləʊʒ(ə)n/Submit
noun
1.
a violent shattering or blowing apart of something, as is caused by a bomb.
I also don't get the rampant hysteria around lithium batteries. Some of it is comical, and like I say people seem to ignore the fact it's being compared against storing and burning litres of petrol.Quote:
Originally Posted by DanceswithUnix
No, I didn't, but you seem to be missing the fact that I was talking about materials where the energy is stored chemically, not in either pressure cookers where, actually, it isn't inherently stored at all, until you apply external heat) or something like pressured canisters where there is indeed stored PE.Quote:
Originally Posted by watercooled
Nor did I say your original statement was wrong. I think you're reading into it something I didn't say.
All I said originally, correctly, was that when a chemical store of potential energy combusts, the difference between whether it's called burning, or combusting, or deflagrating or exploding is the speed with which that reaction occurs. That's nothing to do with, for example, pressure cookers.
Can we agree that lithium cells can burn, aggressively? That they emit light, heat, gases and a pressuee wave?
Suppose you have a given quantity of energy, equivalent to that of a lithium cell, stored in some medium, and it releases that energy by burning. If it releases it over, say, 30 seconds, you have combustion. If it releases it all in, say, a ten-thousandth of a second, you have an explosion.
It's one process, call it combustion, but a vast spectrum of speeds of reaction, with explosion at the far end. Note, that is NOT saying other things, like a pressured canister don't explode, but in the context of chemically stored PE, it isn't what I'm talking about.
Do lithium cells explode? No. They burn, and pretty fast and aggressively, but they don't explode. and even that, only if there's a major fault, or external trauma.
Is there an element of danger? Sure. But so is there in sitting 6 feet from a 30 gallon tank of a volatile liquid like petrol though that too is pretty safe unless there's a major flaw in the tank, or external trauma.
My point was that in any spectrum like this, you have a considerable range of values. Technically, "detonation" is simply a reaction above the point on that spectrum where the pressure wave in the medium exceeds the speed of sound, though that's not the common usage of it, which is more like "cause to go bang", as in "he detonated the bomb". That is not my meaning.
The relevance to this thread?
Only that a tiny little lithium cell the size of a cigarette packet can, when it fails for whatever reason, be it internal flaw or external trauma, produce a rapid and aggressive flame, as in some seconds of an unextinguishable flame several feet long.
It is NOT an explosion. The reaction, while much faster than, say, a burning sheet of paper, is still much closer to the speed of reaction necessary to be an explosion than that sheet of paper, or a burning barbecue coal, is.
Lithium cells, when they fail, do so pretty spectacularly.
So, venting? Of course, many of the risks can be mitigated, and no doubt will be. Venting, either to release gases or even to prevent heat build up? Great.
But .... if it were possible to engineer out all risks, we wouldn't have train or plane crashes, 100+ years after we invented trains or planes. Or petrol fires in combustion-engined cars.
About the only way to be sure to avoid such risks is to never get in a car, train or plane again. Life is one long, never-ending (until death, at least) sequence of small risks.
Forgive me for not knowing what on Earth you're arguing with at this point. I've no idea what you are trying to say as you've contradicted yourself, gone off on a massive tangent, and come around saying literally what I said in the first place! https://forums.hexus.net/hexus-news/...ml#post4051967
If you read what I actually said, and what I was replying to, I was challenging the use of the word 'explosion' when referring to failure of a lithium battery pack and "taking a few blocks in the street" which struck me as hysteria or misunderstanding. If you weren't 'disagreeing' with it, what was the point in your "Ummm .... forgive me for being picky," reply all about? Because it's IMO fairly reasonable to interpret that as a disagreement.
Besides that I'm really not sure what you're agreeing or disagreeing with, what point you're trying to make, or what question you're trying to ask? I've not replied to each statement in your posts for risk of it taking the thread miles off-topic and I assumed most of it was more of a ramble than a call for responses.
Lets just scratch everything and go back to the beginning. I said, more or less, that batteries are designed to fail in a controlled matter so they don't build up pressure and subsequently explode. You've just said:
Are we sorted then?Quote:
Do lithium cells explode? No. They burn, and pretty fast and aggressively, but they don't explode.
Almost. Most of it we never disagreed on.Quote:
Originally Posted by watercooled
Assuming you agree with my above comments about burn, and speed on reaction, then my point, and I thought it was clear, was :-
- the way lithium batteries fail (catatrophically) is a conversion of potential to kinetic energy, mainly in the form of flame.
- that process has a wude-range of variants, with sliw-burn coal and one end and very high explosive at the other.
- it's a range, a spread, a spectrum, of rates of reaction which I generically if inaccurately referred to as rate of burn.
Here's the point I was trying to make. That rate of reaction is pretty fast compared to most things we would generally, in plain english, call "burning". It is not fast enough to be called (again, loosely, using conversational English rather than a technical term, an explosion.
There is a point on that spectrum where colloquially, "burn" turns to "explode.
An event that is jyst one side of that point and one just the other side of it can be not far apart in terms of the speed of the reaction.
Explosions, for instance, are not all equal. Some, like gunpowder, are pretty slow for an explosion, while others like high power military explosive result in a very fast pressure wave indeed.
Similarly, some things (like lithium cells that let go) burn pretty quickly and others, like barbeque coal, very sedately.
So the point - which I described as the difference being speed of burning, is that something very fast on the burning end can be quite close to something very slow for the 'explosion' end.
I wasn't disagreeing with you, about lithium cells not exploding (they don't, though they can burn fast and aggressively) and certainly not about, what was it? ... bringing down blocks of streets.
No, they won't. The pressure wave, well subsonic, doesn't have that sort of energy in it.
But .... if a cigarette-pack-sized cell can produce 10 or 15 seconds of a sustained 3-feet jet of flame perfectly capable of causing serious injury or a proper, for instance, house fire, then the flame a cell or cells capable of powering a car, if failing in the same manner, produced would be quite an impressive flame.
What to you (and me) is not an explosion could conceivably be called one by a passing member of Joe Public that nearly got incinerated, or even badly burned, by it.
"Explosion", I think we've now pretty thoroughly and conclusively established, is a pretty vague and often very inaccurately used term. Which is what I was trying, in a light-hearted manner, to point out.
Well I'm happy to agree to disagree on anything we *don't* agree on! :P
My reason for bringing the whole thing up in the first place, as I said, was more to do with the perpetuated 'myths', I guess you could call them, around lithium cells and many other things. It's easy for people to take something as gospel and repeat it, without actually fact-checking, heck even the media do it. I'm speaking about more than batteries here but it's a shame when rumour, conjecture and plain pseudo-science end up with an equal standing in some peoples' minds to fact, and the more the nonsense is repeated, the more it becomes ingrained. But in some cases the claims can be quite harmful and it's worth challenging them, especially where something is new or poorly understood, and still easy to sway opinion with a bit of hyperbole.
Facts? Actual facts? On the internet?
Whatever next? It'll spoil the whole thing if we start introducing facts.
What do you think this is? Fox News? Daily Mail?
:D
Outside of the usual hysterical discussions about the dangers of Lithium ion cells in cars, do we have any actual examples of where cars have flared up in a manner that is more dangerous than say a ICE car catching fire and flaring up? The only one I can think of is from several years ago when a Tesla where the fire was "extinguished" caught fire again days later.
However I'm sure that during that time a lot more ICE cars caught fire and actually killed people. ;)
They still look like hideously pretentious, spanky, soul-less, Apple-Store reject cack, that no self-respecting driver would want to be seen dead in, though.... and there's still no way to have one in terraced suburbia-land.
What does that comment have to do with the headline or article or any of the comments on this thread?Quote:
Originally Posted by Ttaskmaster
What, aside from the car being fast charging, but there still being nowhere to plug it in at home?Quote:
Originally Posted by badass
None whatsoever. Have a nice day.
Personally I don't tend to refill the fuel tank of my petrol car at home either.
I get what you're saying, and while it might be an issue for some use-cases, having charging points e.g. at work, the shops, etc, you can likely negate the need to charge at home for most people at least.
Personally, I don't think the electric car thing is going to be the overnight change some people seem to expect, rather something that will gradually fade in *when it works* i.e. when it makes sense practically and economically. And that's regardless of that 2040 ICE ban, something I see as more of a PR gesture (and maybe some encouragement for manufacturers, or reassurance that there will be a market for those previously sitting on the fence about taking the plunge) - I mean let's face it, the same body who brought in the law could just as easily revoke or delay it if the market still wasn't ready. The gov't wouldn't want sales of cars to stop overnight if for some reason the deadline hadn't been met! Both sides know that, but you wouldn't want to be one of the few manufacturers who still hadn't bothered to make an effort ~20 years down the line.
Edit: For me, one of the remaining concerns (aside from cost) is about range for the odd long-distance trip, even if the 100-200 mile range is more than enough for everyday trips. Sure, as it stands now you could rent and ICE vehicle or carefully plan the trip to take extended coffee breaks at service stations with charging points, but that's not necessarily a practical solution for a long-distance drive in the countryside where there really aren't any charging points yet, and the hilly terrain means you'll burn through charge more quickly too.
At risk of establishing a dangerous precedent, I entirely agree with watercooled.
The point about charging at work, etc, wouldn't suit me, but then, I'm not in "most" people's circumstances.
A couple of the non-negotiable issues for me are :-
- home charging, and
- the range to do a several hundred mile trip, wirh no more stops than my current ICE vehicle.
By no more stops, I mean 10 mins to refill the tank on a really ,ong run, plus perhaps (if and only if I need it) a 20-min coffee/loo break.
As for charge-at-office .... no office. Well, home office, but my commute is down stairs, along corridor. My office is in my home.
That might be my one chink of disagreement. There are LOTS of people whose working lives don't involve a typical commute-by-car to an office, where a car could be charged. I'm in one category (srlf-employed, work quite a lot from home, but also periodically soending time, sometimes a lot of it, on client's sites
Or rather, I was. I'm now more retired than not. So, even more important is charhing at home.
So for me, a 100km range in 3 minutes is certainly a step in the right direction.
I also kinda agree with ttaskmaster on the (lack of) visual appeal BUT .... frankly, these days don't really give a hoot. If everything else, the performance, range, running costs, assurances of battery longevity, etc, all stacked up, I wouldn't let the visyals stop me. Tjough there are some (typically expensive) attractive leccy-cars.
To be honest, these days, I'm more likely to buy a Rangerover than a Ferrari even if tge Ferrari is drop-dead gorgeous and the Rangerover reminiscent of a 1950's-era block of Soviet flats. Why? Comfort, and I can get in and out with doing my back in.
I'd have no qualms but a butt-ugly, soulless whatever, IF it suited my transport needs and, sadly, my days of driving for enjoyment are probably gone for good. Now, it's about getting from A to B.
That said, if I find an affordable, practical leccy-car that otherwise meets my critetia, gets me from A to B and looks (and sounds) like an Aston Martin, sign me up.
Since this article isn't about a car that means your comment has nothing whatsoever to do with this thread or any of the posts. As I suspected from the first post.Quote:
Originally Posted by Ttaskmaster
Still, I am genuinely curious as to what you were posting about. I assume a car made by BMW or Porsche. Which one? I can think of some cars that could be described that way.
OK, whatever makes you happy.Quote:
Originally Posted by badass
Pretty sure they demonstrated it on a Porsche Taycan, but never mind.