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Mazda's daft fuel saving idea.

Discussion in 'Hobby Electronics' started by Trevor Wilson, Dec 19, 2012.

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  1. **Mazda have announced that next years' cars will be fitted with a
    capacitor, which is charged by the alternator and, in turn, will operate
    the car's electrical system for a period (the alternator will be turned
    off). Assuming a 10 Farad capacitor, I figure that equates to around
    3,000 Watt/seconds of power. Plenty to run a car stereo for a few
    minutes, but, to put it into motive terms, about enough to run the car
    for about 20 Metres.

    Unless the capacitor is very much larger than I assume it is.
     
  2. Don McKenzie

    Don McKenzie Guest

    There are storage systems that have proven to work, such as the KERS
    system in formula one cars:
    http://www.formula1.com/inside_f1/understanding_the_sport/8763.html

    This regenerates the breaking energy back into real forward motion energy.

    I am just wondering if Mazda have used the term capacitor, a little
    loosely in this case.

    Don...


    --
    Don McKenzie

    $30 for an Olinuxino Linux PC:
    http://www.dontronics-shop.com/olinuxino.html

    The World's Cheapest Computer:
    DuinoMite the PIC32 $25 Basic Computer-MicroController
    http://www.dontronics-shop.com/the-maximite-computer.html
    Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
    Arduino Shield, Programmed in Basic, or C.
     
  3. Don McKenzie

    Don McKenzie Guest

    Found it:
    http://www.mazda.com/publicity/release/2011/201111/111125a.html

    Regenerative breaking system to a capacitor:
    http://www.caradvice.com.au/wp-content/uploads/2012/09/Mazda-i-ELOOP1-625x338.jpg

    some capacitor. I wonder what the specs are?

    Don...


    --
    Don McKenzie

    $30 for an Olinuxino Linux PC:
    http://www.dontronics-shop.com/olinuxino.html

    The World's Cheapest Computer:
    DuinoMite the PIC32 $25 Basic Computer-MicroController
    http://www.dontronics-shop.com/the-maximite-computer.html
    Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
    Arduino Shield, Programmed in Basic, or C.
     
  4. Don McKenzie

    Don McKenzie Guest

    Perhaps it's a Flux Capacitor.

    With the world ending tomorrow, it won't be worth while. :)

    Don...


    --
    Don McKenzie

    $30 for an Olinuxino Linux PC:
    http://www.dontronics-shop.com/olinuxino.html

    The World's Cheapest Computer:
    DuinoMite the PIC32 $25 Basic Computer-MicroController
    http://www.dontronics-shop.com/the-maximite-computer.html
    Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
    Arduino Shield, Programmed in Basic, or C.
     
  5. yaputya

    yaputya Guest

    Mazda aren't using the capacitor to drive the car forward, as in an electric vehicle,
    they are recovering some otherwise wasted energy from braking and using it to
    power the auxiliary electrical loads and recharge the main battery. The energy
    saved would have to have been provided by the alternator, which Mazda can
    then apparently unload, further reducing losses.
    They claim benefits in stop-start driving, which makes sense as most real-world
    driving in cities is like that. I would like to see some comparative test results
    before declaring it worthwhile or not though.
     
  6. **All we need to know is the size of the cap used, in order to determine
    it's usefulness. I have heard an unconfirmed report that the cap is
    rated at 1,200 Farad. If the cap is as large as one source claims, then,
    suddenly, the system appears viable.
     
  7. Don McKenzie

    Don McKenzie Guest

    Apparently Maxwells have them:
    http://www.tecategroup.com/ultracapacitors-supercapacitors/maxwell.php

    linked story here:
    http://seekingalpha.com/article/608361-stop-start-realities-and-ev-fantasies

    Don...



    --
    Don McKenzie

    $30 for an Olinuxino Linux PC:
    http://www.dontronics-shop.com/olinuxino.html

    The World's Cheapest Computer:
    DuinoMite the PIC32 $25 Basic Computer-MicroController
    http://www.dontronics-shop.com/the-maximite-computer.html
    Add VGA Monitor/TV, and PS2 Keyboard, or use USB Terminal
    Arduino Shield, Programmed in Basic, or C.
     
  8. yaputya

    yaputya Guest

    After thinking about this a bit more, I guess we could do some basic calculations
    (ball park) to see whether this stop-start capacitor-storage concept is valid.
    (It must be valid or there wouldn't be so much money going into it, eh? It ain't
    like Joh Bjelke Petersen's water-powered car, surely!!!)

    Feel free to correct me if you see a flaw...remember these are ball park calcs.
    A reasonable requirement of a stop-start system would be to store the energy in
    making a single stop in traffic conditions. Let's say a 1000kg car being stopped
    from about 50km/h or 14m/s. The cars kinetic energy is half m v-squared which
    works out at about 200,000 Joules. (m is mass, v is velocity)
    (The rate of deceleration determines the maximum charging current rating
    of the capacitor required to capture all of it.

    A capacitor's energy storage is half C V-squared (C is capacitance in Farads, V is voltage).
    According to the Mazda website their capacitor has a rating of 25V. So in
    order to store 200,000 Joules at 25V the capacitor needs to be at least 640 Farad.
    Using the data from
    http://www.tecategroup.com/ultracapacitors-supercapacitors/maxwell.php
    it seems a 1,200F parallel array of 10 K2-BCAP cells would have rating of 27V and
    an ESR of around 5milliohm. Using ball park calculations this would mean
    an initial charging current from 25V of 70A and time constant of 6 seconds, which
    seems reasonable for braking from 50km/h in normal city driving.
    The K2-BCAP caps can easily handle this current and if fully charged to 25V
    would store 375,000 Joules.
    I leave detailed calculations as an exercise for the student......
     
  9. yaputya

    yaputya Guest

    There is a mistake in the above, a simple SERIES array of 10 1200F K2-BCAP
    cells required to achieve the 25V voltage rating would only have a tenth of the
    capacity of each cell, i.e. 120F instead of 1,200F. However there are other modules
    which come closer to what is required for a viable system.
     
  10. **I already know the Voltage rating and operating Voltage of the system.
    Sorry I neglected to add that earlier. It is 25 Volts. I have been
    informed that the capacitor is rated at 1,200 Farad. If true, then the
    system should accomplish what it is supposed to do. At around 375,000
    Joules of energy storage, there should be sufficient recovered braking
    energy to make a worthwhile improvement to the system.

    My mistake was assuming that energy storages in the order of 1,000 Farad
    (@ 25 Volts) were economically viable, in a small enough package.
    Apparently they are.

    I still have my concerns about stop-start technology, but time will tell
    if it is viable in the market-place.
     
  11. terryc

    terryc Guest

    What is their method for doing that?
     
  12. yaputya

    yaputya Guest

    From http://www.mazda.com/publicity/release/2011/201111/111125a.html

    Regenerative braking systems are growing in popularity as a fuel saving technology. They use an electric motor or alternator to
    generate electricity as the vehicle decelerates, thereby recovering a portion of the vehicle's kinetic energy. Regenerative braking
    systems in hybrid vehicles generally use a large electric motor and dedicated battery.
    Mazda examined automobile accelerating and decelerating mechanisms, and developed a highly efficient regenerative braking system
    that rapidly recovers a large amount of electricity every time the vehicle decelerates. Unlike hybrids, Mazda's system also avoids
    the need for a dedicated electric motor and battery.
    'i-ELOOP' features a new 12-25V variable voltage alternator, a low-resistance electric double layer capacitor and a DC/DC converter.
     
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