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Graphene Super capacitor as battery?

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  1. Jun 3, 2013 #1
    I have been hearing about the possibility of a graphene super capacitor for quite some time now, but it still seems they are not readily available.

    Is there anyway for me to get my hands on one? Would it be possible for me to buy/make one practical enough to replace a AA battery? What size would a graphene super capacitor like this be?

    I have seen videos of people making graphene caps with a lightscribe drive, but I'm not sure that would be plausible for me to make a battery.

    Any information on this would be appreciated. Thanks.
     
  2. jcsd
  3. Jun 3, 2013 #2

    Drakkith

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    Capacitors, even super caps, are not a direct replacement for batteries, as a capacitor's voltage drops off sharply as it discharges. What are you wanting to do with this capacitor?
     
  4. Jun 3, 2013 #3
    I was just hoping to get one to play around with. The fast recharge rate of a cap would be fantastic for many applications. What about lithium-graphene hybrid batteries? I hear they supposedly have relatively fast recharge rates as well as acceptable capacity and energy density. How far are we away from those?


    Thanks.
     
  5. Jun 3, 2013 #4

    Drakkith

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    I'm honestly not sure.
    Why don't you just get a regular capacitor with a very large capacitance?
    Or get several capacitors and put them in parallel.
     
  6. Jun 3, 2013 #5
    I was hoping to benefit from the smaller size of some super capacitors. For any applications I had in mind I was hoping to use it as a fast charging battery that could fit within a volume of about 2 AA batteries or less. Also, I don't think just capacitors in parallel would have enough energy density compared to these new graphene batteries are supposed to have (or the energy density of any battery for that matter).

    I did consider attempting to make some graphene super capacitors with the lightscribe method and put them in parallel as you had suggested, but I am still not sure that I would have sufficient energy density.

    Thanks for your help thus far. Any other suggestions as to how I could get my hands on such a fast charging battery, or will I have to wait a bit for it to hit the market (years :( )?
     
    Last edited: Jun 3, 2013
  7. Jun 4, 2013 #6

    sophiecentaur

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    Unless you have a particular application (??) in mind, I can't see it would be worth while spending money on a 'particularly small' super capacitor. You can do all the electrical experimenting on a full size one and prove to yourself just how inconvenient it nearly always is that
    V = Q/C
    and not
    V = 1.5Volts, for a simple battery, over most of its charge cycle.
    Of course, there are always circumstances where a capacitor will win but steady supply volts are usually what we want.
     
  8. Jun 9, 2013 #7
    I was going to use it as a battery for a small electric heater (not sure how much of a problem the varying voltage would be). Thanks.
     
  9. Jun 9, 2013 #8

    Bobbywhy

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    algar32, Here are two articles about new battery designs:

    One such company is XG Sciences, Inc. based in Lansing, MI. It has launched its offering, which features a graphene-hybrid material for use in the anodes of Li-ion batteries. The company claims that the anodes will result in Li-ion batteries that have four times the capacity of today's conventional anode batteries.
    http://spectrum.ieee.org/nanoclast/...logy/graphenebased-liion-anodes-go-commercial

    and,

    “Hybrid ribbons of vanadium oxide (VO2) and graphene may accelerate the development of high-power lithium-ion batteries suitable for electric cars and other demanding applications."
    http://phys.org/news/2013-03-hybrid-ribbons-gift-powerful-batteries.html
     
  10. Jun 10, 2013 #9

    sophiecentaur

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    Sounds ideal. :-)
     
  11. Jun 10, 2013 #10
    Thanks. I came across the XG sciences article before. The other article was quite interesting as well. Hopefully they release a commercial product sometime within the next few years.
     
  12. Jun 10, 2013 #11
    Thanks. So you think that this could be plausible to power a small electric heater?

    What do you think the best way for me to approach this would be?

    Do I have to wait for the industry to put out a graphene super capacitor "battery", or is it possible for me to make one myself that would meet me needs?

    Do you think I would be able to make anything practical via the lightscribe method:

    Thanks for your help.
     
    Last edited by a moderator: Sep 25, 2014
  13. Jun 10, 2013 #12

    CWatters

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    You had better start at the beginning...

    How much power must the heater generate? 1W? 10W? 100W? 1kW?
    How long do you want it to work for between charges?

    Once you have an idea of the power required and how long it must be delivered you can work out how much energy the battery needs to store.

    Only then can you decide what sort of battery/storage is required or even if it's feasible.

    It's perhaps worth noting that each new battery technology developed since about 1980 has initially only provided about a factor of 2 improvement, then as the technology improves further small improvements are make. Perhaps your expectations are too high?
     
  14. Jun 10, 2013 #13
    Not sure how much power I need yet. I need to find the resistance of my heating element and run some current across it to see if I can get to the desired temps. Unfortunately, I will not have access to a quality lab bench supply until about 2.5 weeks from now. Once I have collected my data I will post back.

    Also, could anyone comment on the lightscribe diy graphene super caps I posted above. Using that method would it be possible to make a semi viable super cap battery out of several graphene super caps (I know it's all relative without any of the above information yet)?

    Thanks for your help.
     
  15. Jun 11, 2013 #14

    sophiecentaur

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    You must surely have an idea of the number of Joules of energy you need. 1J or 1MJ? Without this, it's a non starter. "Resistance" is entirely secondary.
     
  16. Jun 11, 2013 #15

    CWatters

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    According to one report the original paper on laserscribed graphene caps claimed they achieved 3.67 millifarads per cubic centimeter.

    The data for an Energiser AA battery says that an AA cell has a volume of about 8 cubic cm so you might manage to make a capcitor with a capacitance of aound 30 millifarads (30 x 10^-3F).

    I've no idea what voltage they would withstand but for your own safety you should restrict it to about 35-40V. That's about the safe limit above which an electric shock can potentially kill you (although it's actually the current that matters).

    Anyway lets assume you can use 40V. In that case the max energy you can store in the capscitor is...

    E = 0.5 C V^2
    = 0.5 * 30 x 10^-3F * 40^2
    = 24 Joules

    So if your heater has a 1W power output it would run it for 24 seconds.

    A typical LED burns around 24mW so it might power one of those for around 1000 seconds or 16 mins.

    The power output won't be constant unless you use a regulator or similar.

    Your mileage may vary!
     
  17. Jun 11, 2013 #16

    CWatters

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  18. Jun 11, 2013 #17

    sophiecentaur

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    Any regulator should be incorporated in the heating element (for efficiency). But the actual application is highly relevant. If you just need to heat something up then why have a regulator at all? A thermostat is all you'd need.
     
  19. Jun 11, 2013 #18

    CWatters

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    Indeed. My comment about the regulator was really just a reminder that the voltage wouldn't be constant.

    Likewise on an electric car the speed controller might be able to deal with the changing voltage.
     
  20. Jun 11, 2013 #19

    sophiecentaur

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    As with all engineering, the requirement comes before the solution or one may be disappointed.
     
  21. Jun 13, 2013 #20
    Agreed. I just don't know that I can give a specific number in joules. If I had to guess (without any basis of measurement), I would say it will consume 10-12 watts of power for hopefully around 5 to 10 seconds (at least at first, It would be nice for it to heat longer, but for proof of concept I would be happy with this time).

    I am not sure if this is possible with a reasonably sized (contained with 2"x1"x1") graphene supercapacitor for this amount of power for this long of time. I know caps have a high power density, but a problematically low energy density.

    I was hoping you could tell me if this would be possible based on my estimated power consumption.

    Thanks for your help.
     
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