It's started

begreen Posted By begreen, Jul 5, 2017 at 10:59 AM

  1. georgepds

    georgepds
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    The graph has more to do with battery chemistry than cars.

    On the issue of battery power you can design for power or energy or something in between. In the lead acid world there are starter batteries(power) storage batteries (energy) and something in between( marine)
     
  2. begreen

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    What about combining battery with a supercapacitor for motive power and acceleration?
     
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  3. Ashful

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    Yes, of course! It will only be a matter of time before one of the automakers starts paralleling these attributes in a power storage unit, to provide the best of both worlds. I just hope it's under $100k, when it happens.

    We are living in a second golden era of ICE cars, now. For the first time in history, the average person can buy a car which will perform on-par with the elite supercars of two decades past. I can't help feeling like it's the final crescendo, though... I doubt our kids will drive sports cars with 600 hp ICEs, unless they're wearing antique plates.
     
  4. spirilis

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    I was thinking about that the other day. Right at the dawn of the EV revolution, we've finally perfected the gasoline ICE... Life is ironic that way.

    (Recent news about Mazda's new HCCI, i.e. gasoline-running-like-diesel engine really drove this sentiment home)
     
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  5. jharkin

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    Exactly.

    Car starting batteries are designed for high specific power using sponge like lead plates that provide a lot of surface area to support a fast chemical reaction. The downside is less active material resulting in a lower total capacity per cycle. Deep cycle batteries are build with thick solid lead plates for the opposite reason.

    The same effect in lithium battery design. My batteries experience is with R/C hobbies where we use lithium polymer batteries that a built to handle charge rates up to 5C (i.e. 12 minute recharge) and discharge rates up to 30C+ burst (i.e. use the entire capacity in 2 minutes)... The downside is that they have less capacity per weight/volume than the typical lithium cell from a laptop/phone/car thats optimized for much lower charge rates. And they dont last nearly as long.

    Typical high end hobby battery is a 3Ah-5Ah brick wired for 22.2v (6 cell) or 44.4v (12 cell)..... Discharge rates run into the hundreds of amps over a 3-5 minute run time then users recharge them in 15-20 minutes. Abused like that packs last a few hundred cycles over a year or two, max.

    The big power density isn't really needed in cars other than the fact it supports a faster charge. Your 300 mile range Tesla driven at 60mph works out to a very mild C/5 average discharge rate. BeGreen's idea about pairing a battery with capacitance might be a solution for the peak load issue.
    But isn't that generally true with every technology wave? - it reaches a peak of refinement right as sometime better comes along (either because we have run out of ideas to improve it, or the something better made further refinements moot).
     
  6. georgepds

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    Re caps.
    They do something like that in portable versions of the navy rail gun

    59E3S7y_d.jpg
     
  7. georgepds

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    Rail gun... more on power vs energy

    https://www.reddit.com/r/WarshipPorn/comments/39wsc1/the_naval_railgun_faq_is_finished_heres_a_taste/

    "A 64 MJ shot is equivalent in energy to just a few gallons of marine diesel (accounting for inefficiencies when converting to electricity and then to kinetic energy). About 300 laptop batteries. But batteries put out too little power.

    "When firing, the [30 MJ prototype] draws an average ~12.5 GW(3% of the US grid). They need a hefty power supply to store and then release that energy.
     
  8. begreen

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    That'll dim the lights in the neighborhood.
     
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  9. woodgeek

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    Memories. :rolleyes:

    A buddy and I once played around with building 'mini-railguns' using a 3 kJ HV capacitor he bought surplus from NASA. I think we estimated that we got peak currents of 100,000A and peak powers of 100 MW (for a few tens of microseconds). The graphite rail gun projectiles always just vaporized without any obvious acceleration. Boring. We made a Lenz effect accelerator...a 2cm 20 turn solenoid (at 100 kA) put a lot of speed on a copper projectile (penny). Of course, the solenoid itself was destroyed by each 'shot'....its copper conductor fragmented into uniform ~1mm pieces due to the magnetic stresses from the pulse (and, um, were blown clear across his dorm room). We hypothesized this was the speed of sound in copper times the duration of the shot.

    We closed the circuit with a pinball rolling down a chute onto two copper nails. ;lol
     
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  10. georgepds

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    The economist agrees with you about the end of the ICE

    https://www.economist.com/news/leaders/21726071-it-had-good-run-end-sight-machine-changed-world-death?cid1=cust/ednew/n/bl/n/20170810n/owned/n/n/nwl/n/n/na/54751/n
     
  11. georgepds

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    The current rail gun barrels weigh 15 tons... helps a bit with barrel erosion
     

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