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This discussion relates to Technology Review's article Better Batteries Charge Up.

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  zakir.ak
  

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  08/05/2008 01:45 AM

  need fast charging time

  high density battery packs are a boosting field. i think it is in the right direction of future transportations. the main concern is about the time taken to charge the batt-back. last week LOTUS GT introduced it's 700 horse-power Electric Vehicle which charges up in just 10 minutes for a 200 mile run! this will be challenge for all high density automobile battery designers

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  • 
    dasein
    

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    08/05/2008 12:56 PM

    Re: need fast charging time

    When they quote a mileage run, say 200 miles, does that mean without a radio, air conditioner or headlights on? If so, what reasonable reduction can you assume with any or all of these items in play?

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    DGDanforth
    

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    08/05/2008 06:25 PM

    Re: need fast charging time

    A short charging time means high current.
    One way to achieve this is by discharging a charged EESU into an empty one.  But notice that the resultant two EESUs will come to equilibrium holding 1/2 of the original charge in each unit.  Hence to have the uncharged  EESU come to equilibrium at 350 volts it is necessary for the precharged EESU to be charged at a higher voltage.  If we assume there is no loss in energy in the charging process (a false assumption) then we need to equate energy before and after the equilibrium state.  If V is the larger voltage of the 'charger' and v is the equalibrium voltage of the two units and noting that the energy in a capacitor with capacitance C is 1/2 C v^2 then we must have
    1/2 CV^2 = 1/2 Cv^2 + 1/2 Cv^2
    or
    V^2 = 2v^2
    or
    V ~ 1.4v
    For v=350 volts we find the 'chargers' voltage must be equal to or greater than
    
    V = 490 volts
    
    As long as that voltage is much smaller than the breakdown voltage of the unit all is well.
    
    I just thought one should realize that the 'home charging unit' must operate at 490 volts in order for the car's unit to operate at 350 volts.

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    • 
      davack
      

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      08/06/2008 09:25 AM

      Re: need fast charging time

      Great observation.  It is actually voltage that will be high rather than current.  Breakdown voltage was demonstrated in the test to be over 1kV.

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    • 
      rr999999999
      

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      08/06/2008 09:54 AM

      Re: need fast charging time

      That 630 voltage for houses would be a savings for the home owner.  People make a mistake of having just 220 for their home.  In the long run they pay more for their electricity.  

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      • 
        GoatGuy
        

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        08/07/2008 09:53 AM

        Re: need fast charging time

        630 VAC in the home?  Are you F***NG nuts?  120 VAC in the US is admittedly low, but pretty darn safe.  220 in "the Continent" and elsewhere is 4x more lethal ... and uses less copper for a given amount of power.  Just about at the limit of voltage versus the Common Man.  630?  If a single ground-leak were to happen within a kitchen appliance, you'd be fried well before you could jerk your hand/arm/butt away. 

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    • 
      biosubs
      

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      08/07/2008 12:26 AM

      Re: need fast charging time

      DGDanforth, thank you for the tutorial.
      
      I trust your comments assume that the charging circuit that sits between the two EESUs are simple wires. 
      
      Are you aware that when used in the automotive application there is a rather sophisticated "smart" inverter/charger that takes the 3500 volts delivered by the EESU at full charge and reduces it to the voltage needed by the drive motor (probably 200-300 volts AC, probably 3 phase to optimize starting from a dead stop) to do whatever the driver asks of it?  This  inverter also takes the electrical energy produced during regenerative braking and puts it back into the EESU.
      
      Also, the EESU is actually a ceramic capacitor, not a chemical battery, so charging time is minutes if the charging system can provide the power to do the job quickly.  Unlike chemical batteries wherein chemical changes are involved in charging he battery, no chemical changes are involved in the charging of a capacitor.   With the proper circuitry interposed between two EESUs, it is possible to top off a capacitor receiving charge at 3000 volts from an EESU operating at well under 3000 volts.  

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    • 
      GoatGuy
      

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      08/07/2008 10:29 AM

      Re: need fast charging time

      Holy Toledo! Who said anything about 330, or 1000 volts or any other charge-up voltage?  Capacitor dielectrics are rated in volts-per-meter (or mm, or micro), but that does NOT imply that a PARTICULAR amount will be in a given capacitor. There is absolutely no hint as to the working voltage of these purported ultra-caps.
      
      The rest of your analysis is essentially correct, but it also loses a different point: that voltage is the integration of current over time divided by capacitance.  This is the limit of voltage no matter what.  So, the issue really becomes one of "what practical limit on a constant current basis can the ultracaps be charged at?" 
      
      Say that an EV has a bank of ultracaps hooked up to hold 100,000,000 joules of energy (at 0.5 Mj/km, equates to 200 km of range), and a rated full-charge voltage of 343 volts (343 = 1.414 x 240, or the peak full-wave-bridge voltage from rectifying a 240 VAC standard service line without transformers.  A PRACTICAL goal).
      
      P = ½CV²
      100,000,000 = ½ C 343²
      C = 1,700 FARADS at 343 volts.
      
      Nominal discharge at 100 km/hr is 50 MJ/hr or 50,000,000 J/hr, or 13,888 J/sec (=watt)
      
      OK, 13,888 watts at the HIGH charge of 343 volts limits out at 40 amps or so. Not alarming. Good actually.
      
      At 50% charge (343 x sqrt(50%) = 240 volts), amps has to go up to 57 amps. And so on.  10% left ... 127 amps.
      
      How big would the constant amps have to be in order to charge the vehicle in 5 minutes?
      
      343 volts
      300 sec
      = 1.14 volts/sec
      V = I/C  (for constant I & C)
      I = VC = 1.14 x 1700 = 1,933 AMPS.
      
      Almost 2,000 amps?  Any idea how BIG the darn cables have to be to carry that without significant resitive power loss?  Really big. 12 gauge carries 40 amps safely enough over short distances. So, 50 of those in parallel, with a liquid coolant... One hell of a cable for the common "filling station" to keep fit and sound.
      
      Further ... what if the ultracap "goes critical"?  Ever shorted out even a modest sized conventional electrolytic cap?  As a fearless kid, I shorted out a 0.022F cap energized at 140 V with a screwdriver.  P=½CV² = 0.011 x 140x140 = 200J.  Completely destroyed the screwdriver and just about deafened me. Now, let's talk 100 MEGAjoules.  That's the explosive power of 24 kilograms of TNT! 
      
      THAT, good folks, is something to be concerned about. Because capacitors, "ultra" or conventional, don't have a non-lossy mechanism for slow, safe discharge.
      
      Great idea, but the calcs show the practical problems with the technology.  I'm FOR IT, but I don't think the basic claims of "5 minute charge" and "300 km range" are realistic.
      
      GoatGuy

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  • 
    bigrobhollins
    

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    03/30/2009 08:46 AM

    Re: need fast charging time

      battery packs might be necessary; but what about this:
       you sit in the drivers seat and are confounded by the second handbrake.. you find out that it's the pump for the starting motor. see, you provide the mechanical motion thru which the electrically inert system responds with energy.  here's the task list: a high-output electrical motor to power vehicle systesm, an energy reservoir as capacitor, some peak-voltage spark-like design to impell or begin or start the 'car', and that's about it.  it could eventually technologically scale itself down to that push-button. it's like how older cars had to be handcranked..  stopping the car would be as easy as turning it off, but, cars may never truly 'stop' again; it'll be like driving a battery that only needs mechanical maintenance and whatnot.

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• 
  zig158
  

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  08/05/2008 06:02 AM

  something is fishy

  I have been following EEStor for a few years now, and there activities seem very suspicious. Why are they unable to demonstrate a prototype? They clam to be close to mass production, but they can’t create a single device in a lab environment, something is fishy.
  
  I hope their product is real and wish them the best, but I will believe it when I see it.

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  • 
    asdar
    

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    08/05/2008 06:52 AM

    Re: something is fishy

    They've only been in the public eye a few years. Why would anyone open themselves up to being copied or criticized for a product in development. They certainly don't want to lose control by making a public offering of stock.
    
    In my opinion he's handled the whole situation perfectly. Get just the funding you need, prepare for mass production, then come out with a demonstration.
    
    I think a lot of people that claimed to know that EESTor's product wouldn't work will be eating crow soon. You'd think the scientific community would at least have an open mind.

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    • 
      CapacitorMan
      

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      08/05/2008 08:00 AM

      Re: something is fishy

      It's not that we don't have an open mind, its that the little bit of technology revealed in the patents and published applications so far appear to be in direct contradiction to known phenomena.

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      • 
        biosubs
        

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        08/07/2008 12:30 AM

        Re: something is fishy

        Probably so.  It is likely that everything to be known about the physical world is already known and everything that will ever be invented has aleady been invented.
        
        Really?

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  • 
    irreverent
    

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    08/05/2008 09:41 PM

    Re: something is fishy

    Why are they moving into EVs first, why not do some proof of principle in smaller electric devices just like A123 did with cordless tools. It does sound suspicious.

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  • 
    davack
    

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    08/06/2008 09:27 AM

    Re: something is fishy

    Good thing delivery is now 2009 and not 2015.

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  • 
    GoatGuy
    

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    08/07/2008 10:42 AM

    Re: something is fishy

    I agree.
    
    If their tech works, then why not a little "amazing demo can"?  You know, a AA battery sized cap, filled with their stuff, showing 10,000 joule capacity (3x lithium), and say a breakdown voltage of 30 volts. 
    
    If P=½CV² ... then 10,000=½CV² then C needs to be 220 FARADS, for that can.  Can they do it?  That's all I would need to "be a believer".  I mean really!!!  They've been working on the "research" side for 3+ years.  How about a single, cobbled together, compact capacitor having even "the same" energy-capacity per cc as a lithium cap?
    
    To those who say, "they don't want to let the product technology out of the bag", that's just bull.  PATENT protection covers their arses there, and well.  They just need to show that the actual, practical capacity of their device(s) is about 100x that of today's ultracaps.  You can buy a commercial 50F, 17 volt ultracap today that measures about 5cm diameter, and 15 cm length.  That corresponds at full charge to 24 J/cc.  The lithium ultra-battery stores about 800 J/cc. So, there's the goal.  800 x 3 = 2400 / 24 = 100x!
    
    No demo cap?  As far as I'm concerned, then the technology is "pie-in-the-sky", or an ongoing 'technology/science boondoggle' that gets lucrative investment capital, mills out science papers at a tolerably convincing rate, excuses its lack-of-demo devices as premature-because-of-unfinished-safety-research, and keeps going for years, decades.
    

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    • 
      voluntaryist
      

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      10/11/2008 05:59 PM

      Re: something is fishy

      GoatGuy: I will reserve judgment until Jan. 2010. If they keep delaying year after year I would say their creditability should reach zero by 2015. Why have they done so poorly with the Zenn? The Zenn is nothing like they are promising. Why didn't they wait until they could deliver something closer? I will be watching the next generation Zenn. If it works like they say it will, I will be the first to buy one.

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      • 
        GaryB
        

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        02/13/2009 01:58 PM

        Re: something is fishy

        We all wish EEStor well, but it's smelling fishy. This article was back in Aug ... now Feb 09 and counting.  People think because some big companies are involved that proves something.  Remember those AAA rated mortgage backed securities.  Big companies, "experts", big money on the line ... and mud in our face.
        
        Exactly what does EEStor lose by demo'ing?  They aim for cars first instead of say laptops or power tools?? Or, energy can be dangerous.  If you've got something so good, go for grid storage first rather than consumer apps. I don't get it.
        
        I hope it's true, I hope I'm wrong, but perpetual machines would be really cool too.

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