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HONDA FCX Ultracapacitor

Discussion in 'Battery Discussion' started by wolfgang, Oct 3, 2006.

  1. wolfgang

    wolfgang Guest

    HONDA claim to have incorporated in their FCX Concept fuel cell car, a proprietory ultracapacitor. According to their graph, this module stores up to 2 kWh/kg and delivers 1.7 kW/kg. These numbers look too good to be true, a 20-fold improvement in energy density of the Tesla roadster's battery pack. To store 50 kWh would only require 25 kg of mass!

    Also, NESSCAP are selling 5 kF ultracapacitors with only 1/3 of a 18650's energy density.

    So how did HONDA do it? Or is there a typo in HONDA's graph?
  2. klausefluoride

    Sep 14, 2006
    Woah. But if Honda could build this, why bother with the fuel cell at all?
  3. danny

    danny Administrator

    Aug 15, 2006
  4. tevvybear

    tevvybear New Member

    Nov 4, 2006
    the question is, how much self-discharge would that ultracapacitor have? Self-discharge has always been a noticeable problem with electrolytic capacitors, though i don't know about these ultra-capacitors.
    If it discharges itself by even 10% per day, problems of overall energy efficiency arise
  5. WarpedOne

    WarpedOne Supreme Premier

    Aug 17, 2006
    Slovenia, Europe
    IIRC maxwel states for their 3000+F ultracaps, that they loose about 1% of charge in a month.
  6. asdar

    asdar Member

    Aug 17, 2006
    I'm not an electrical engineer so I may have this totally messed up.

    I believe that there's some kind of problem with scaling up ultracapacitors. The numbers on the Honda were 2 grams/watt I think.

    Like I said, I don't know what I'm talking about on this, but the factor that doesn't scale is the K factor, which I think is the dialectric coefficient.

    I'm not sure why you couldn't just have 1,000 2 gram capacitors or something along those lines and still get the finished product of 2kg instead of 2 g.

    If there's someone that knows more I'd love to see an explanation from an expert.
  7. Roy

    Roy New Member

    Jan 12, 2007
    The Honda Ultracapacitor cannot be 2 wHr/g but must be 2wHr/kg as it shows the ultracapacitors as only being marginaly better than standard capacitors. Also I couldn't find any mention of a 5 kF capacitor at Nesscap.

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