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Using Ultra Capacitors to Replace Batteries

Discussion in 'Electronic Design' started by D from BC, Jul 16, 2007.

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  1. D from BC

    D from BC Guest

    Ultra capacitor example:
    http://www.elna.co.jp/en/ct/pdf/DZNe.pdf
    10F
    2.5V
    18mm x 35mm
    About $30.00 at digikey.

    Question is.... Are these ultracaps replacing batteries in some
    designs?

    Maybe implemented in a cordless optical mouse or Mp3 player?

    Can ultracaps outperform batteries?
    D from BC
     
  2. Damon Hill

    Damon Hill Guest

    Depends...capacitors can have high power density (they can deliver
    large amounts of current for a short time) but only very small amounts
    of current for longer periods. Batteries have high energy density,
    delivering small to medium (and sometimes high) currents for much
    longer periods.

    If the current drain is >very< small, they can replace batteries in
    some instances; otherwise they can supplement batteries. Capacitors,
    properly designed and used, can endure constant and high charge/discharge
    rates, which batteries don't like.

    If ultracaps could operate at substantially higher voltages, they
    could store much more energy but probably never as much as batteries.
    Both capacitors and batteries are improving, so I think we'll see more
    of both being used, often in tandem.

    --Damon
     
  3. The energy density of a common alkaline battery is 1000 times higher,
    and the cost is 100 times lower.
    Only as a short term power source.
    1000 times is too much of a difference.


    Vladimir Vassilevsky

    DSP and Mixed Signal Design Consultant

    http://www.abvolt.com
     
  4. Good answer.
     
  5. Gary Tait

    Gary Tait Guest

    Maybe. Either for backup, or where their discharge is not critical.
    I have seen them used for RTCs, and in some shake flashlights.
    Nope. Li-Po batteries can do those.
     
  6. Eeyore

    Eeyore Guest

    Not to *replace* batteries, no.

    Not normally, although the ultra caps used in regenerative braking systems in
    electric vehicles have the advantage of being able to accept charge faster than
    a battery will.That's the only reason they're there.


    Graham
     
  7. Yes and no. They cannot store as much energy, but they can
    charge and discharge much faster. There are certainly applications
    where an ultracapacitor could replace a battery. I have considered
    using them for a low drain application where they could be instantly
    recharged by plugging (very) briefly into an automotive power supply.
    It would require a capacitor with a low leakage current.
    A more come design would be to use both. Alkaline batteries can
    lose their charge very fast if they are subjected to a heavy current
    drain even for a short period of time. Using a capacitor along with
    the battery can extend the battery life since the capacitor can handle
    the large but short high current requirement.
     
  8. AZ Nomad

    AZ Nomad Guest

    bullshit.

    Your typical ultracap can only push few milliamp. Fine for holding CMOS memory,
    but you're not going run a UPS.

    To charge a farad in under an hour requires the ability to push a few amps.
     
  9. Guy Macon

    Guy Macon Guest

    Content-Transfer-Encoding: 8Bit


    It has been a few years since I used ultracaps, so somebody please
    correct me if this is no longer true, but when I used them the
    ESR was *very* high and thus the available current was quite low.
    The combination of a large capacitance and a high ESR made it so
    that I couldn't put a newly-built PWB on a test fixture and test
    the board's ability to hold data during a power failure -- the
    test was over before the ultracap had time to charge. I had to
    add a test to the burn-in fixture. Likewise on the discharge;
    short it out for a minute or so and find that it is still charged.

    Wikipedia has an interesting energy density chart:
    [ http://en.wikipedia.org/wiki/Energy_density ]

    A few selected items from the list:

    ENERGY DENSITY IN MJ/kg:
    -------------------------------------------------------
    Spring...........................................0.0003
    Capacitor........................................0.002
    Supercapacitor...................................0.01
    Ultracapacitor...................................0.02
    Lead-acid battery................................0.09–0.11
    EEStor Ultracapacitor (claimed capacity).........1.0
    NiCd Battery.....................................0.14-0.22
    NiMH Battery.....................................0.22
    Zinc-air Battery.................................0.40-0.72
    Lithium ion battery..............................0.54–0.72
    Wood.............................................6.0–17.0
    Flywheel........................................l0.5
    Lignite coal....................................14-19
    Cowdung/Cameldung...............................15.5
    Methanol........................................19.7
    Ethanol.........................................30.0
    Anthracite coal.................................32.5
    LPG.............................................34.39
    Diesel fuel.....................................45.8
    Gasoline........................................46.9
    Hydrogen.......................................143
    Uranium-235 (nuclear fission)...........90,000,000
    Hydrogen (nuclear fusion)..............300,000,000
     
  10. Hal Murray

    Hal Murray Guest

    It has been a few years since I used ultracaps, so somebody please
    That's what I would have said a few months ago. But a friend
    gave me a heads-up. They are now competing with batteries
    for things like electric cars.


    http://www.worldandi.com/subscribers/feature_detail.asp?num=23938

    Known for storing a short-lived jolt of electricity
    essential to the successful operation of electrical circuits
    in devices and appliances ranging from PCs to microwave ovens,
    cell phones, and televisions, the capacitor is in the midst of
    a major, ongoing upgrade of its energy storage capabilities.
    After nearly two centuries in which batteries have been the
    obvious choice for storing usable amounts of energy, high-end
    capacitors, known as ultracapacitors, are poised to challenge
    them in a growing range of applications.


    http://www.technologyreview.com/NanoTech/wtr_16326,303,p1.html

    A breakthrough technology is holding forth the promise of
    charging electronic gadgets in minutes, never having to replace
    a battery again, and dropping the cost of hybrid cars. Indeed,
    the technology has the potential to provide an energy storage
    device ten times more powerful than even the latest batteries
    in hybrid cars -- while outliving the vehicle itself.
     
  11. dav1936531

    dav1936531 Guest

    Has anyone actually had a production or product sample from EEStor. I
    hear about this "unbelievable" capacitor technology they "have", but I
    am wondering at what stage of developement these guys really are in.

    I have a product that desparately needs their device (if it works as
    rumor says), but have yet to see anything concrete from them. They
    don't even have a web site.
    Dave
     
  12. Eeyore

    Eeyore Guest

    They don't have a product yet AIUI.

    Graham
     
  13. Here's more detailed specs on another module from the same
    manufacturer:

    http://www.maxwell.com/ultracapacitors/products/modules/bmod0018-390v.asp

    17.8F, with max current 950A at 390 volts, which is more than 370kW.

    Applications:

    * Regenerative Braking
    * Torque Assist Systems
    * Engine Starting




    Best regards,
    Spehro Pefhany
     
  14. amdx

    amdx Guest

    Another EEstor Ultracapacitor story.
    http://www.technologyreview.com/Biztech/18086/?a=f
    Mike
     
  15. 1 Farad charges at 1V per second at 1 amp.
     
  16. SP

    SP Guest

    Please watch your attributions. I did not write any of the above.

    Best regards,
    Spehro Pefhany
     
  17. Sorry, I thought I had done so... You quoted AZ, and I quoted you
    quoting him (I think).

    I could not access the original post, so I replied to yours.

    Anyway, sorry for any confusion.
     
  18. As others have indicated, you are behind the times. Current
    products do handle high current pulses.
     
  19. Damon Hill

    Damon Hill Guest

    Another important difference between batteries and capacitors
    is the flatness of discharge voltage; a battery is nearly flat
    over most of its range. I don't think a capacitor, no matter
    how large, will be remotely as flat. This has interersting
    implications in motor controller designs, for example.

    --Damon
     
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