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Capacitor to mitigate charge taper

Discussion in 'Model S: Battery & Charging' started by JPUConn, Aug 17, 2016.

  1. JPUConn

    JPUConn Member

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    why doesn't tesla enable full use of whatever is being plugged into and manage tapering with capacitors?

    I always equate charging the tesla battery to filling up a glass of water with a garden hose and understand the purposes of tapering but just thinking they could effectively speed up supercharging times with a capacitor or series of capacitors managing enabling the supercharger to continue to crank.

    Will become more meaningful with more volume of vehicles hitting superchargers.
     
  2. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    A single supercharger cabinet can produce 135kW more or less all day long. It tapers because of the batteries in the car. As the SOC of a battery increases, so does the resistance. Overcoming this resistance to continue to charge the battery creates heat. That heat needs to be removed, and there is a limit to the cooling systems in the car. Charging too quickly can cause the batteries to explode or catch on fire.

    I'm not sure I understand how capacitors would help, unless you're suggesting that Tesla add them in the battery pack? This has been discussed before; a hybrid pack of batteries and super capacitors.
     
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  3. JPUConn

    JPUConn Member

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    Capacitors on the vehicle - apologies if this was posted before. Mods pls delete this thread
     
  4. hiroshiy

    hiroshiy Active Member

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    I'm not professional in this area but have basic knowledge.
    http://lab.bitluni.net/cap
    This site calculates capacitor farads into Wh which we all are familiar with. 6000F Nichicon Supercapacitor is about 1.3kg, diameter 76.2mm height 165mm. Assume you discharge it from 2.5V to 500mV, then this equates to 3.3Wh, which gives you about 60 feet of rated range. You would need 100 of them to run 1 mile.

    Basically supercaps are for idle-stop applications in ICE automotive. When the car is close to stop, stop the engine. When the gas pedal is pressed, use the supercap to run the motor for like a few seconds to save gas.
     
  5. andrewket

    andrewket 2014 S P85DL, 2016 X P90DL (soon 100)

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    There are capacitors that can store kWh of energy. The challenge is the cost per kWh is not yet at a point to make it feasible for an EV.
     
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  6. Sir Guacamolaf

    Sir Guacamolaf The good kind of fat

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    Thats a pretty good explanation. Imagine if we had 250,000F supercapacitors, one on each wheel, capturing regen power, that would probably make a huge difference to the range. Only problem is, we don't have 250KF super capacitors.
     
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  7. David99

    David99 Active Member

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    capacitors don't help. Batteries are perfectly capable of capturing and delivering high power required by a high performance EV like the Tesla. Only at high levels of charge and when continuously used are there some limitations. Capacitors are much worse in terms of energy density and charge/discharge behaviour. It would be wasting space and adding more complex electronics to switch between batteries and capacitors smoothly.
    I think the improvement in cell chemistry and a better cooling system will take care of the rather conservative Supercharging speed soon.
     
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