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Help with energy returned in an HEV

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  • Arcologic@aol.com
    Hi, guys, I know I have a lot of experts here-- how about a little help? My impression is that you get back 50% of the energy stored during regenerative
    Message 1 of 9 , Apr 1, 2006
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      Hi, guys,

      I know I have a lot of experts here-- how about a little help?

      My impression is that you get back 50% of the energy stored during
      regenerative braking. It might break down like this--

      Wheels to generator shaft: 90%
      Generation: 85% (to DC)
      Battery: 70% returned as DC
      Power to shaft: 85%
      Shaft to wheels: 90%

      Overall regen cycle efficiency: 0.9 x 0.85 x 0.7 x 0.85 x 0.9 = 0.41

      Oops, looks like the cycle efficiency is 41%. But, this is optimistic, I
      think-- my understanding is that regen is only fully effective in no-brake
      stopping. (Hey, I own a diesel, haven't had personal contact with HEVs.)

      So, how am I doing here, do I have the picture about right? How does the
      kind of battery affect the numbers? Is my transfer from mechanical to electric
      (DC) too low at 85% ?

      Ernie Rogers



      [Non-text portions of this message have been removed]
    • biogasoline
      Hi Ernie, Your calculations are about right, but perhaps a little too optimistic about battery energy return, That could be as low as 40%. Here is why. The
      Message 2 of 9 , Apr 1, 2006
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        Hi Ernie,

        Your calculations are about right, but perhaps a little too
        optimistic about battery energy return, That could be as low as 40%.
        Here is why.

        The chemical battery can accept charge and deliver charge only so
        fast.

        The supercapacitor on the other hand can accept charge and deliver
        charge faster.

        If there is more power being generated than the battery can rapidly
        accept, then that extra regenerative power is lost forever┬ůsince it
        never actually gets captured in the battery.

        Here is a prior article I wrote about super-capacitors:

        Remember, that a super-capacitor cannot simply be paralleled with a
        battery. For maximum storage, the VOLTAGE MUST VARY WILDLY from V max
        at full charge to V min at full discharge. So high power and very
        efficient power conversion electronics will be required to make
        this "breakthrough: possible.
        First, an input inverter must convert whatever charge voltage is
        available to a voltage that is slightly higher than whatever is
        already in the super-capacitor. (voltage to voltage inverter)
        Then, the super-capacitor inrush current must be regulated so that
        the current is delivered at a charge rate that does not excessively
        load the input power source capabilities. (Input current regulation)
        Then the desired output voltage must be supplied at the constant
        voltage desired by the load, while the voltage across the super-
        capacitor must be allowed to vary wildly with its charge discharge
        cycle!(buck-boost voltage regulator).
        Lastly, the output current demand must be met while preventing damage
        to the output regulator or the super-capacitor itself from short
        circuit conditions.
        ( output current regulator with fold-back current limiting and
        electronic circuit breaker action).
        While super-capacitor technology is racing forward at a fantastic
        pace, we should prepare ourselves by proceeding to develop the
        required power conversion electronics for our immediate applications.
        Only with efficient and appropriate low-loss synchronous switching
        power conversion electronics already added to existing applications
        will super-capacitors become "Drop In Solutions" to become our long
        sought but heretofore only theoretical solution to meet our "Ideal
        Battery" requirements.



        With Best regards,
        FREE ENERGY
        Patrick Ward
        Richmond, VA
        fossilfreedomATyahoo.com fossilfreedom@...
        fossilfreedomATyahoogroups.com fossilfreedom@yahoogroups.com
        biogasolineATyahoo.com biogasoline@...
        biogasolineATyahoogroups.com biogasiline@yahoogroups.com

        http://www.fossilfreedom.com

        --- In future-fuels-and-vehicles@yahoogroups.com, Arcologic@... wrote:
        >
        > Hi, guys,
        >
        > I know I have a lot of experts here-- how about a little help?
        >
        > My impression is that you get back 50% of the energy stored during
        > regenerative braking. It might break down like this--
        >
        > Wheels to generator shaft: 90%
        > Generation: 85% (to DC)
        > Battery: 70% returned as DC
        > Power to shaft: 85%
        > Shaft to wheels: 90%
        >
        > Overall regen cycle efficiency: 0.9 x 0.85 x 0.7 x 0.85 x 0.9 =
        0.41
        >
        > Oops, looks like the cycle efficiency is 41%. But, this is
        optimistic, I
        > think-- my understanding is that regen is only fully effective in
        no-brake
        > stopping. (Hey, I own a diesel, haven't had personal contact with
        HEVs.)
        >
        > So, how am I doing here, do I have the picture about right? How
        does the
        > kind of battery affect the numbers? Is my transfer from mechanical
        to electric
        > (DC) too low at 85% ?
        >
        > Ernie Rogers
        >
        >
        >
        > [Non-text portions of this message have been removed]
        >
      • Arcologic@aol.com
        Forgive my persistence-- I posted the following message on Saturday and got only one response (because it was the weekend?), so I am posting it again. /Ernie
        Message 3 of 9 , Apr 3, 2006
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          Forgive my persistence-- I posted the following message on Saturday and got
          only one response (because it was the weekend?), so I am posting it again.
          /Ernie

          Hi, guys,

          I know I have a lot of experts here-- how about a little help?

          My impression is that you get back 50% of the energy stored during
          regenerative braking. It might break down like this--

          Wheels to generator shaft: 90%
          Generation: 85% (to DC)
          Battery: 70% returned as DC
          Power to shaft: 85%
          Shaft to wheels: 90%

          Overall regen cycle efficiency: 0.9 x 0.85 x 0.7 x 0.85 x 0.9 = 0.41

          Oops, looks like the cycle efficiency is 41%. But, this is optimistic, I
          think-- my understanding is that regen is only fully effective in no-brake
          stopping. (Hey, I own a diesel, haven't had personal contact with HEVs.)

          So, how am I doing here, do I have the picture about right? How does the
          kind of battery affect the numbers? Is my transfer from mechanical to
          electric
          (DC) too low at 85% ?

          Ernie Rogers



          [Non-text portions of this message have been removed]
        • murdoch
          I m sorry that I don t presently have numbers for you, but at present I don t. I do think that the rationale for adopting supercaps, as the one response
          Message 4 of 9 , Apr 4, 2006
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            I'm sorry that I don't presently have numbers for you, but at present
            I don't. I do think that the rationale for adopting supercaps, as the
            one response suggested, is in part to increase efficiency. I'll also
            try to keep your questions in mind if I find myself speaking to
            someone who might be of assistance.

            Maybe Forbes can help a little when he gets a chance, since he is
            familiar with the charging aspect, even if that is not identical to
            the quick charge-discharge going on in a non-grid-chargeable-hybrid.



            On Mon, 3 Apr 2006 13:34:55 EDT, you wrote:

            >Forgive my persistence-- I posted the following message on Saturday and got
            >only one response (because it was the weekend?), so I am posting it again.
            >/Ernie
            >
            >Hi, guys,
            >
            >I know I have a lot of experts here-- how about a little help?
            >
            >My impression is that you get back 50% of the energy stored during
            >regenerative braking. It might break down like this--
            >
            > Wheels to generator shaft: 90%
            > Generation: 85% (to DC)
            > Battery: 70% returned as DC
            > Power to shaft: 85%
            > Shaft to wheels: 90%
            >
            >Overall regen cycle efficiency: 0.9 x 0.85 x 0.7 x 0.85 x 0.9 = 0.41
            >
            >Oops, looks like the cycle efficiency is 41%. But, this is optimistic, I
            >think-- my understanding is that regen is only fully effective in no-brake
            >stopping. (Hey, I own a diesel, haven't had personal contact with HEVs.)
            >
            >So, how am I doing here, do I have the picture about right? How does the
            >kind of battery affect the numbers? Is my transfer from mechanical to
            >electric
            >(DC) too low at 85% ?
            >
            >Ernie Rogers
            >
            >
            >
            >[Non-text portions of this message have been removed]
            >
            >
            >
            >
            >Yahoo! Groups Links
            >
            >
            >
            >
            >
            >
          • murdoch
            This somewhat technical article happened to come up in conversation on other matters. Perhaps it will be of some use in digging up numbers for you to use for
            Message 5 of 9 , Apr 4, 2006
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              This somewhat technical article happened to come up in conversation on
              other matters. Perhaps it will be of some use in digging up numbers
              for you to use for some of your equations. Unfortunately, it's
              focused on ultracaps (Maxwell's name for supercapacitors, or whatever
              we're calling them today) but I think it can be decent background
              research for us.

              http://www.maxwell.com/ultracapacitors/support/papers/electric_drives.html

              On Mon, 3 Apr 2006 13:34:55 EDT, you wrote:

              >Forgive my persistence-- I posted the following message on Saturday and got
              >only one response (because it was the weekend?), so I am posting it again.
              >/Ernie
              >
              >Hi, guys,
              >
              >I know I have a lot of experts here-- how about a little help?
              >
              >My impression is that you get back 50% of the energy stored during
              >regenerative braking. It might break down like this--
              >
              > Wheels to generator shaft: 90%
              > Generation: 85% (to DC)
              > Battery: 70% returned as DC
              > Power to shaft: 85%
              > Shaft to wheels: 90%
              >
              >Overall regen cycle efficiency: 0.9 x 0.85 x 0.7 x 0.85 x 0.9 = 0.41
              >
              >Oops, looks like the cycle efficiency is 41%. But, this is optimistic, I
              >think-- my understanding is that regen is only fully effective in no-brake
              >stopping. (Hey, I own a diesel, haven't had personal contact with HEVs.)
              >
              >So, how am I doing here, do I have the picture about right? How does the
              >kind of battery affect the numbers? Is my transfer from mechanical to
              >electric
              >(DC) too low at 85% ?
              >
              >Ernie Rogers
              >
              >
              >
              >[Non-text portions of this message have been removed]
              >
              >
              >
              >
              >Yahoo! Groups Links
              >
              >
              >
              >
              >
              >
            • murdoch
              Here s another one. http://www.automotivedesignline.com/howto/181503995;jsessionid=GYXK2FSLELUVSQSNDBGCKHSCJUMEKJVN?pgno=2 Same author-company. They talk
              Message 6 of 9 , Apr 4, 2006
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                Here's another one.

                http://www.automotivedesignline.com/howto/181503995;jsessionid=GYXK2FSLELUVSQSNDBGCKHSCJUMEKJVN?pgno=2

                Same author-company. They talk about comparing "turnaround
                efficiency" of ultracaps versus batteries. If we knew their exact
                definition, I think we'd be getting somewhare.

                Again, clearly, this is coming from a company with an interest in the
                outcome of discussions (for that matter, it's one of the companies I
                have to disclaim that I cover in my other work, though that list is
                getting long, so I'm not sure what to do about that... I think I may
                have to institute a more-occassional group disclaimer and let it go at
                that).

                "At very high pulse power levels the ultracapacitor is still operating
                at efficiency levels greater than 50%. In fact, battery chemistries
                are not capable of the power-to-energy ratios achievable with an
                ultracapacitor and will have turnaround efficiencies well below 50%
                for high pulses."
              • beard6801@bellsouth.net
                I did some playing around with the idea of ultracaps awhile back.....My understanding of the problem is this: Yes you can capture some of the energy from
                Message 7 of 9 , Apr 4, 2006
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                  I did some playing around with the idea of ultracaps awhile back.....My
                  understanding of the problem is this:

                  Yes you can capture some of the energy from regenerative braking.....but you
                  suffer conversion losses just as you do from motive power....

                  But the biggest stumbling block is that the batteries by their nature can
                  only be charged at a certain rate before they are overstressed. During
                  regenerative braking you have a high amount of energy available for a brief
                  time period, and the batteries are only able to take in a small portion of
                  what is available...

                  because of the differences in batteries and ultracaps......ultracaps are
                  superior for capturing this higher energy. They are inferior for storing the
                  energy as they self discharge rapidly.....

                  So the best solution is a hybrid pack that contains both Batteries and
                  Ultracaps. Unfortueneately, doing this adds complexity to the
                  system.....batteries are two way devices, energy in or out in both
                  directions, while ultracaps are one directional only....you put enegy in one
                  side and take it out the other. it is not as simple as just hooking them in
                  parralel...

                  you will need BMS, a charge controller, and a buck/boost controller for
                  switching between the batts, and the caps....

                  The benefit is a much more dynamic system with better acceleration, longer
                  range because of the superior regenerative braking, and longer battery life
                  because the caps buffer the batteries from higher demands in both
                  acceleration and regen...

                  The downside is allot of additional cost, because you have batteries plus
                  ultracaps, plus the additional controller, plus the additional integration
                  issues and proper sizing of all the components....

                  David W. Beard
                  ----- Original Message -----
                  From: "murdoch" <murdoch@...>
                  To: <future-fuels-and-vehicles@yahoogroups.com>
                  Sent: Tuesday, April 04, 2006 3:27 PM
                  Subject: Re: [future-fuels-and-vehicles] Re: Help with energy returned in an
                  HEV


                  >
                  > This somewhat technical article happened to come up in conversation on
                  > other matters. Perhaps it will be of some use in digging up numbers
                  > for you to use for some of your equations. Unfortunately, it's
                  > focused on ultracaps (Maxwell's name for supercapacitors, or whatever
                  > we're calling them today) but I think it can be decent background
                  > research for us.
                  >
                  > http://www.maxwell.com/ultracapacitors/support/papers/electric_drives.html
                  >
                  > On Mon, 3 Apr 2006 13:34:55 EDT, you wrote:
                  >
                  > >Forgive my persistence-- I posted the following message on Saturday and
                  got
                  > >only one response (because it was the weekend?), so I am posting it
                  again.
                  > >/Ernie
                  > >
                  > >Hi, guys,
                  > >
                  > >I know I have a lot of experts here-- how about a little help?
                  > >
                  > >My impression is that you get back 50% of the energy stored during
                  > >regenerative braking. It might break down like this--
                  > >
                  > > Wheels to generator shaft: 90%
                  > > Generation: 85% (to DC)
                  > > Battery: 70% returned as DC
                  > > Power to shaft: 85%
                  > > Shaft to wheels: 90%
                  > >
                  > >Overall regen cycle efficiency: 0.9 x 0.85 x 0.7 x 0.85 x 0.9 = 0.41
                  > >
                  > >Oops, looks like the cycle efficiency is 41%. But, this is optimistic, I
                  > >think-- my understanding is that regen is only fully effective in
                  no-brake
                  > >stopping. (Hey, I own a diesel, haven't had personal contact with HEVs.)
                  > >
                  > >So, how am I doing here, do I have the picture about right? How does the
                  > >kind of battery affect the numbers? Is my transfer from mechanical to
                  > >electric
                  > >(DC) too low at 85% ?
                  > >
                  > >Ernie Rogers
                  > >
                  > >
                  > >
                  > >[Non-text portions of this message have been removed]
                  > >
                  > >
                  > >
                  > >
                  > >Yahoo! Groups Links
                  > >
                  > >
                  > >
                  > >
                  > >
                  > >
                  >
                  >
                  >
                  > Yahoo! Groups Links
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                  >
                • Gil Dawson
                  Hi, David-- ... Whoa, there. I was under the impression that capacitors -- ultra or not -- have only two terminals, just like a battery. In fact, the two
                  Message 8 of 9 , Apr 5, 2006
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                    Hi, David--

                    At 6:07 PM -0400 4/4/06, <beard6801@...> wrote:
                    >batteries are two way devices, energy in or out in both
                    >directions, while ultracaps are one directional only....you put enegy in one
                    >side and take it out the other. it is not as simple as just hooking them in
                    >parralel...

                    Whoa, there. I was under the impression that capacitors -- ultra or
                    not -- have only two terminals, just like a battery. In fact, the
                    two terminals are labelled the same, plus and minus.

                    Using the model I learned in college (shortly after the invention of
                    the kerosene lamp), it seems to me that, with a capacitor or a
                    battery, you put in and take out by changing the voltage presented at
                    those terminals, so that the current flows either into or out of the
                    device. In this sense batteries and capacitors would be very
                    similar. They are also similar in that there is a breakdown voltage
                    defined for each device, above which you break it. They are also
                    similar in that that breakdown voltage is on the order of a couple of
                    volts per cell, so you have to stack cells in series to get those
                    high voltages we love in our cars. (A 12-volt battery contains six
                    cells in series, does it not?)

                    The biggest difference between capacitors and batteries that I recall
                    is that the amount of energy stored in a capacitor is proportional to
                    the square of the voltage, whereas the amount of energy stored in a
                    battery is a matter of some debate. (You'd think that knowing a
                    battery's voltage and temperature would tell you how much energy is
                    in it, but then there's "memory".)

                    Another difference between capacitors and batteries is the current
                    rating. You have to baby batteries, to give the chemistry time to
                    work things out. But capacitors function with faster-acting physics,
                    so they can take huge rushes of current without complaint. I think
                    it is this feature that is called "power density", because huge
                    current means huge energy per unit time, which means huge power -- in
                    or out.

                    The distinction of chemistry for batteries and physics for capacitors
                    suggests that there might one day exist overlap devices. But not
                    yet. As far as I know, there is no ambiguity among any devices made
                    today. Like cats and dogs, when you look at one, you know which it
                    is. So far.

                    It makes sense that we cannot simply hook them in parallel, but what
                    goes between them? This must be the buck/boost controller of which
                    you speak. What a quaint name. How does this gadget work? Could it
                    be a SPDT switch, controlled by a computer? I wonder what factors
                    the computer might use to decide which way and when to throw the
                    switch? How much energy does it consume?

                    I'm reading
                    http://www.maxwell.com/ultracapacitors/support/papers/electric_drives.html .
                    Perhaps there will be more answers there. Do we know the authors of
                    this piece?

                    --Gil
                  • murdoch
                    ... I interviewed Richard Smith of Maxwell on behalf of EVWorld.com about five years ago. I d characterize him as seemingly very good in both business and
                    Message 9 of 9 , Apr 5, 2006
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                      >I'm reading
                      > http://www.maxwell.com/ultracapacitors/support/papers/electric_drives.html .
                      >Perhaps there will be more answers there. Do we know the authors of
                      >this piece?

                      I interviewed Richard Smith of Maxwell on behalf of EVWorld.com about
                      five years ago. I'd characterize him as seemingly very good in both
                      business and technical areas. I met with him again a few years later
                      at a conference and he helped me go over a few more things about
                      Maxwell's product, including its use as a load-leveler (probably my
                      overly simplistic term) in such areas as fuel cells and wind.
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