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Super-fast EVCPs?

I don't think that I have seen this in here before, but these batteries came up in a motoring forum.


The claim to charge an EV all the way in 5 min seems to be entirely spurious - all that they have managed so far is a moped, but even if the batteries existed, how would they be charged?


Here is my back-of-a-fag-packet calculation. An average EV will do 4 - 5 miles per kWh; let's be conservative and say 4. So with a range of 300 miles between charges, that requires 75 kWh. Delivered over 1/12 hour that requires 900 kW. So in round terms, that is one 1 MVA transformer per EVCP. Could be useful on a motorway, but I cannot see the point elsewhere. Even then, very few journeys in UK are over 300 miles. Both Edinburgh and Land's End are closer to Birmingham than that.


900 kW at 48 V DC is almost 20,000 amps. What sort of connexion is envisaged?
  • Chris Pearson:

    I don't think that I have seen this in here before, but these batteries came up in a motoring forum.


    The claim to charge an EV all the way in 5 min seems to be entirely spurious - all that they have managed so far is a moped, but even if the batteries existed, how would they be charged?


    Here is my back-of-a-fag-packet calculation. An average EV will do 4 - 5 miles per kWh; let's be conservative and say 4. So with a range of 300 miles between charges, that requires 75 kWh. Delivered over 1/12 hour that requires 900 kW. So in round terms, that is one 1 MVA transformer per EVCP. Could be useful on a motorway, but I cannot see the point elsewhere. Even then, very few journeys in UK are over 300 miles. Both Edinburgh and Land's End are closer to Birmingham than that.


    900 kW at 48 V DC is almost 20,000 amps. What sort of connexion is envisaged?


    Regardless of the battery voltage, Mode 4 (DC rapids) charge at up to 500 V DC, or even, using a CCS2 connector, up to 1000 V DC. Current delivery us up to 400 A.


    So the sums look a little better now, at least for the vehicle to EV charging equipment connection ...


    Yes, you are right MW range transformers are required for this kind of kit.


    Coming soon to a filling station near you?


  • Hopefully not Graham,

    Rather have the Hydrogen first!
  • Hydrogen is highly explosive and certainly not 'green' energy due to the losses in producing the stuff.
  • Jon,

    Of course Hydrogen is explosive (IIC) just easier to ignite than the petrol, diesel (IIA) and other traditional automotive fuels that we have globally as well as the UK.


    Is the energy required to manufacture and produce EV Chargers, Electric vehicles and in particular the batteries any "Greener" than a on site electrolysis plant to produce Hydrogen? The greatest idea is the electrical energy is produced by solar/wind and stored and thats then used to produce the Hydrogen stored on site.


    EV's are certainly not the only solution, just one of many solutions to wean away from traditional hydrocarbon fuels and sooner more people understand that the better.

  • I imagine these are another  example of devices that combine the functions of a rechargeable battery and electrolytic capacitor on the same plates, we have seen them in much smaller form as pulse power sources at work. and in the non military world. there are folk making capacitors that can crank an engine for example. Mind you at the moment it is little more than  an expensive proof of concept, but the fact that the capacitance can be made big enough that it can be done at all is interesting, it is a long way from 'swiss rolls' of aluminium foil and waxed paper of not soo long ago - well I can remember it anyway.


    Assuming for a moment that EVs become as popular are petrol engines, you have the megawatts problem anyway, as to charge a town full of cars overnight, or one at a time at a few minutes each still takes the same total energy, and most towns have only a limited number of transmsission and distribution transformers But for 'jump charging' it starts to look practical for the AA man to have a trailer full of transfer battery to rescue folk who have run out of fuel, and it changes the size any service station or garage forecourt needs to be.

    Not far from me Fleet services has 12 pumps, and at peak each one fills a car in about 2-3  mins, and the limiting factor is the staff on the tills, not the size of the pipes to the tanks.

    If a quick charge takes an hour, then you have to have bays for perhaps 30 times more cars, so 300-400 bays to meet the same demand, and society has to stump up for all those man hours of folk waiting for their car to be topped  up at however many pounds a minute.

    The rate of petrol delivery compares to a small power station, so pylon fed supply and suitable transformers will be needed.


    Also I imagine that the pressure will be to move the voltage you can charge a car at upwards, from the current 400V phase to phase, and maybe on board motive power batteries moving to 800V or so already in formula E (from the current 300-500 V depending on maker.).


    As a starter for ten, currents at 690/1k2 3 phase are much more manageable than at 230/400 - if not we will be into water cooled connectors and cables, or multiple connectors to keep them below a weight that can comfortably be lifted. Induction charging will fall by the wayside as  unsafe at high power density.

    (And in practice something not much more than a better shrouded  BS4343 plug with pilot lines can be made to handle a few KV phase to phase. Of course current regulation does not permit, but regulations are a purely human creation, unlike the hard physics of ohms law and joule heating, so I see regulations changing first.)


    HGV  is something else that will need big currents....

    Certainly as of now, EVs only work because most folk do not have one.

    M.
  • So we not going to be driving about our cars with solar panels and mini windturbines on the roof rack  anytime soon? ?
  • gkenyon:

    Regardless of the battery voltage, Mode 4 (DC rapids) charge at up to 500 V DC, or even, using a CCS2 connector, up to 1000 V DC. Current delivery us up to 400 A.



    So the sums look a little better now, at least for the vehicle to EV charging equipment connection ...


    Yes, you are right MW range transformers are required for this kind of kit.


    Coming soon to a filling station near you?




    Graham, thank you. Once again, in here every day is a learning day.


    1000 A at 1000 V is massive, at least by domestic standards - a couple of orders of magnitude bigger. It makes me wonder how safety can be assured for an ordinary user.


    Coming soon? Not if the pair of InstaVolt units less than 1/4 mile away are anything to go by. I have seen them in use only a couple of times over the past few years. They appear to be out of place in a residential area.


  • mapj1:

    Certainly as of now, EVs only work because most folk do not have one.


    Yes indeed, although 1:6 of new car sales in UK last year were battery electric vehicles.


  • Safety for the user  is not as big a deal - batteries at around the KV level can be made to be no more dangerous than a fuel tank. What is needed is isolation mechanisms to chop the pack into isolated shorter strings if there is a fault condition or a serious crash. The other aspect is current limiting. Current car battery pack designs however  are something to behold -

    The Tesla S as a 'high performance' example has a battery built up from many many small cells....

    each cell is an 18650 of about 3 amp-hours capacity.

    (that part no means  an 18mm diameter cylinder, 65mm long, so to visualise it has a  similar aspect ration to  a stick of two  C cells  )

    Each cell is 4.1 to 4.2V when fully charged, and more like 3.5 when run down.

    Now a car has 7104 of these cells

    arranged as 96 series by 74  parallel cell s (to make ~ 402 volts at full charge ) .

    ( so a single module is 3.5 to 4V or so  but 220 AMP-HOURS !!!)

    The economy 60-kWh battery option uses fewer of the same 74 cell parallel modules (to make "just" 352 volts, needing 'only' 6216 cells)

    Other car makers vary quite a bit, but the basic requirement for large numbers of small cells in series parallel stacks is always the same.

    The 'gaps' between the cylindrical cells in the modules are not wasted by the way but used to circulate cooling fluids (forced air  or liquid depends)


    connectors are something else and need pilot contacts  and interlocking to ensure dead or at least no more than exposed ELV when unmated.

    And 3 phase is better than DC for arcing and power density for a given weight of copper.

    personally I see something near to an AC supply of  690/1k2 as a possible future sweet spot in terms of the cross-over between sensible connector pin sizes at lower current, and the level of insulation needed at higher voltages.


    M.
  • If my back-of-an-envelope calculation is correct, the speed of filling an IC car with petrol is very roughly the equivalent of charging an EV at 10MW.