What is a Lithium-ion capacitor?(www.jtekt.co.jp)
42 pointsby ksec6 hours ago6 comments
  • rpaddock2 hours ago
    For anyone that wants to see a real data sheet:

    Nominal Voltage: 4.0V High Power and Energy Densities Cycle Life > 50K Cycles Capacitance Range: 10F-1200Farads

    https://abracon.com/product-lineup/frequency-control-timing-...

    Note that the original data sheets said that these could be wave soldered. ABSOLETLY NOT. Even hand soldering they must be treated with respect, a lot of respect.

    One of the major problems with these is there a minimal voltage that they must not go below. Their life gets shortened. I've never seen data on how much.

    To my knowledge Li-Ion Capacitors were first introduced to the market by Taiyo-Yuden in 2010. They are no longer in this market. I wrote a blog about it back then:

    http://blog.softwaresafety.net/2010/11/introducing-lithium-i...

  • SoftTalkeran hour ago
    Large, charged capacitors are pretty frightening. Batteries too, but their discharge rate is limited to the speed of the chemical reaction.
    • LoganDark39 minutes ago
      Are capacitors not limited by a chemical reaction?
      • SoftTalker35 minutes ago
        Not AFAIK. A simple capacitor is two metal plates separated by an insulator, allowing an electrical charge to accumulate. Discharge would only be limited by the current-carrying capacity of the wiring.
      • saintfire30 minutes ago
        Limited by material. They store electric charge by using thin layers of insulating material and pooling negative charge on one side and positive on the other. You can puncture the material and release energy as a typical conductor, it's not stored chemically.
      • modeless34 minutes ago
        Not generally, no. Capacitors usually store electrons in a conductor so they are free to move instantly. Movement of free electrons within a conductor is not considered a chemical reaction.
      • 34 minutes ago
        undefined
  • supertroop2 hours ago
    Dumb question but I though capacitors store energy and not power?
    • aftbit32 minutes ago
      Power is just the time derivative of energy, like velocity is the time derivative of position. Both batteries and capacitors store energy, which they can release at some given peak and average power. Batteries tend to focus more on energy density (energy stored per weight), while capacitors tend to focus more on power density (rate of energy stored or released per weight).
      • mikepurvis22 minutes ago
        I think that just reflects that the typical usage for a capacitor is smoothing out some very spiky load that runs at a high frequency, say a microcontroller running at 100MHz. The average power needs of the MCU are low, but it's drawing almost all of it in a big burst on every clock tick (10ns).

        Power supplies handle that badly, and the pulses turn your supply traces in a big antenna and suddenly you're an unlicensed FM radio station.

        So for the capacitor that's put in place to buffer that load, the total capacity is important, but what really matters is that the part can manage that 100MHz charge/discharge cycle.

    • azornathogron2 hours ago
      They store energy but there's a limit to how quickly you can get that energy out, hence a limit to power. And I suppose you can kinda talk about them "storing power" in the sense that power is what you might be interested in getting out of them.

      At least, that's my understanding of it.

    • martinbfinean hour ago
      [dead]
  • mrDmrTmrJ2 hours ago
    Let's say you want to make a hybrid car lighter-weight. Where is this useful?

    Power density and cycle life are truly impressive. Energy density is super low

    • ricardobeat2 hours ago
      Interestingly it seems to have some applications for high peak power and regen, they had a car in the Dakar rally:

      https://www.jtekt.co.jp/e/products/capacitor/capacitor_mobil...

      https://www.jtekt.co.jp/e/engineering-journal/assets/1019/10...

    • colechristensen2 hours ago
      You would use these to provide peak power in a system that had short term power needs that were high above the average power needs AND had that power requirement as a bottleneck. Energy is the bottleneck for cars though, not power. unless you're wanting your prius to accelerate like a ferrari

      Maybe it would be useful for less losses with regenerative braking? These would presumably be able to charge much faster and then trickle that power out to the normal battery. You'd need actual power numbers for a car to determine if it would be useful or not.

      In other words this is for "boy I wish I didn't have to have so much extra battery capacity in order to get the power I need" situation which... cars don't have. Maybe in F1?

      • marcosdumay2 hours ago
        > unless you're wanting your prius to accelerate like a ferrari

        That's the point of a hybrid.

        • dcrazyan hour ago
          It’s the best part of any electric drivetrain. Especially when you can remap the throttle to really launch from zero. :)

          (I find that electric acceleration makes highway merging much safer.)

          • LoganDark36 minutes ago
            My EV has the opposite problem, something like half throw is full throttle and then the rest of the pedal does nothing. They do it for marketing reasons but I still don't like it
    • traverseda2 hours ago
      Regen braking,
  • LorenPechtel3 hours ago
    And no mention of the self discharge rate.
    • 3 hours ago
      undefined
    • rpaddock2 hours ago
      For a similar part in this class:

      Low Leakage Current as small as 1µA Low Self-discharge rate, 72 hours @ discharge <5%

      https://abracon.com/datasheets/AHCR-S04R0S.pdf

      The more the Farads the higher the leakage. The higher the tempature the higher the leakage.

  • 3 hours ago
    undefined