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Thread: BMW Porsche fast charger delivers 100km range in 3 mins

  1. #17
    Senior Member watercooled's Avatar
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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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.
    Last edited by watercooled; 14-12-2018 at 07:44 PM.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by Tabbykatze View Post
    Watts are volts x amps. A KVA == KW, it's the same unit...
    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".

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by watercooled View Post
    is expressed as cos phi
    Cos phi(l is an idiot).

    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?

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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!

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by eHM View Post
    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.
    It's not a game changer. It *could* be, but the caveats are easily big enough to knacker it.

    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...?
    BH6, BX6 2.0, BE6, BE6-II 2.0, ST6-RAID, BE6-II 2.0 (again), BD7-RAID, BD7II-RAID, IC7-G, IC7 Max3, AB9 QuadGT, IX38 QuadGT. IX58... Oh, b*ll*cks. RIP Abit

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by DanceswithUnix View Post
    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.
    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.

    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
    Last edited by philehidiot; 16-12-2018 at 01:28 AM. Reason: Extra information / uninformed opinion

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by philehidiot View Post
    Austrialian engineer's point of view on this:
    https://www.youtube.com/watch?v=w_OYbZzWk5E&t=0s
    "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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by watercooled View Post
    Lithium batteries don't 'explode' in the conventional sense, they burn rapidly when they're badly damaged. ....
    Ummm .... forgive me for being picky, and a bit late but it's 9pm Christmas day, so naturally the TV is cr.... rubbish.

    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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    Quote Originally Posted by DaMoot View Post
    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.
    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 Saracen999 View Post
    Ummm .... forgive me for being picky, and a bit late but it's 9pm Christmas day, so naturally the TV is cr.... rubbish.

    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 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?

    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
    Last edited by watercooled; 26-12-2018 at 12:28 AM.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    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.

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    Re: BMW Porsche fast charger delivers 100km range in 3 mins

    @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.

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