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Help with electric car idea

Discussion in 'Electrical Engineering' started by mike, Aug 6, 2005.

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  1. mike

    mike Guest

    I have an idea for an electric car that although is not new, I simply
    have not seen anyone go in this direction. Since I am only a hobbyist
    type of engineer, I and embarrassed to ask if perhaps I am barking up a
    wrong tree. Please bear with my ignorance as I ask a few simple
    questions and give you a brief description of my ideas.

    I do not like the current crop of hybrid cars. although the technology
    is better than nothing at all it is only a minor benefit over none at
    all, and frankly almost all the hybrid cars would be better off as a
    efficient 4 cyl car, without any electrics.

    I think they (the car manufs) have it all backwards. I envision an all
    electric driven wheel car, with a small 200-400 CC engine running on any
    type of fossil fuel (Diesel propane, natural gas, and or petroleum).
    this is a small unit designed to run at the most efficient speed (2500
    RPM). It runs all the time it is needed to charge the batteries and
    also runs the Air conditioner, and any other "power" accessories that
    might be needed.

    The batteries would be of efficient lithium ion type (probably 1-2
    thousand of them). they could be arranged into any needed voltage
    levels. As well as the battery power and the electric engine (Could be
    dc or AC brushless) there would also be a shared shaft DC engine with
    completely different winding sharing the same shaft as the primary
    windings. what this secondary winding would do (Either AC or DC) would
    be to kick in when a large boost in power (initial acceleration and or
    passing at hwy speeds) is needed. I would like to ask if there is any
    large capacity capacitors that could be used to store energy and allow
    for a dump of 3-7 seconds of boost. Are capacitors available that are
    small. lightweight, and of sufficient size that they could be used in a
    gang style connection?

    The little 200-400 CC engine could be run all the time or only when the
    caps are not full. The little engine would first fill the caps, then
    maintain the caps charge. After that the engine would charge the Li ion
    cells. It is also able to take a charge from the AC wall outlet, so
    that during the night your car would be fully charged. The little engine
    in the back could be used to charge when an AC wall outlet is not
    available and of course during the operation of the car to recharge the
    caps. What I really want is a minimum 20 HP equivalent from the main Li
    Ion batteries, and a 50 hp boost as the caps dump to the booster winding.

    Does any of this make any sense? I do not know if I am describing it
    properly, and I beg your indulgence re my lack of formal engineering...
    But I am reasonably capable of machine shop use, and I have a couple
    of "well off" friends who might be interested in funding a prototype.
    Whet I do not know is if such capacitors exist in the size and weight I
    might need.

    Any ideas, would be appreciated...

    If you could.... A CC to my email address of would be
    appreciated....

    Thanks in Advance.
     
  2. SQLit

    SQLit Guest

    As for your battery choice.
    http://www.batteryuniversity.com/parttwo-34.htm

    Seems the lithium batteries do not like it warm. Nor cycled very often.
    That leaves out a lot of the densely populated areas of the south and west
    for sales.
    Lets see each cell weights ~2 ounces times a thousand equals about 125
    pounds. Probably not enough power there to go to the corner. It runs in
    my mind that the GM EV batteries weighed about 2000 pounds. Your concept is
    a long way from 20 horse power.
    I personally have seen my share of capacitors go nuclear in industrial
    settings. I would not choose to get into a vehicle with them as part of the
    power circuit. Wonder what would happen in an accident greater than a fender
    bender. The utilities use caps for power factor correction. They are beefy
    and make one hell of a bang when the grenade.

    Sorry to be the doubting Thomas, but I think your idea is full of holes. To
    many holes to be salvaged. Do you have any voc tec schools near? Check with
    them and see if they have an electric program. Go volunteer for awhile. Then
    maybe you will have a flash that can be called genius. That's what I did.
    Sure awakened me up. I even volunteer for the universities solar racer once
    in awhile. That baby cooks, 80 mph for 20 miles. Does not meet DOT specs
    and can not be driven at night. There are no headlamps. Donated parts are
    now approaching 6 million bucks.
     
  3. Guest


    You are still describing a hybrid. The first hybrids were better than
    the current ones since they had smaller engines. The problem is
    Americans still want performance and that requires energy. You still
    can't get something for nothing.
    Basically a hybrid only tends to level out the energy demand. If this
    is stop and go driving, without too much drag racing there is a big
    saving to be had but if you keep your foot in it, you are burning
    energy and thay has tro come from somewhere.
    At interstate speeds that saving, starts to fall off.
     
  4. night dalits

    night dalits Guest

    That type of car is in design for the last 10 years. One issue was a
    electric motor on each tire, or one central one.

    Google it.
     
  5. Bob

    Bob Guest

    Warning! Rant ahead!
    Move on if you don't have the time!

    There is a basic problem with all of these ideas. Convenience. We want
    to be able to get in our vehicles, drive to where we want to go, and
    get out after we park it. Occasionally we will put up with stopping to
    refuel, but many studies have shown that if it is any less than every
    250-300 miles or so, people consider that a nuisance. That is why you
    see 25+ gallon fuel tanks on monster SUVs that get 10MPG. Those people
    don't care about economy, they just don't want to stop at the gas
    station every 2 days to refill. ELECTRIC VEHICLES CURRENTLY AVAILABLE
    THAT NEED TO BE PLUGGED IN FOR RECHARGE AT THE END OF EVERY TRIP HAVE
    NEVER TAKEN OFF BECAUSE OF THIS. Even the "power pack" idea is
    impractical. If I had to stop and swap out power packs every 2 days, I
    would trash that thing in under a month!

    Hybid cars are not just about recharging the batteries in as much as
    providing a usefull range. The big problem with electric powered
    vehicles has always been range. You can go 70, maybe 100 miles
    betwween recharges, but then the recharge process takes too long to be
    usefull for most commuters. Internal combustion engines are actually
    quite good at converting chemical energy to motion at a constant rate,
    but are extrememly inefficient for acceleration torque and idling,
    making them wasteful for stop-and-go traffic. The hybrid is a way of
    supplementing the lack of range of the electric motor by having the
    gas engine take over for the long hauls when they can operate at peak
    eficiency. The electric motors provide better acceleration efficiency
    and can allow the entire system to shut down when not moving at all.

    Having the internal combustion engine idle continuously and soley to
    keep recharging batteries is just increasing the wastefulness. You
    lose 25-30% of the available stored chemical energy in the conversion
    process alone. In addition, 400cc's of I.C.E. will net you about 5kW
    (6.7HP) of generated electric power under the best of conditions. If
    you are running even just 20HP of electric motor, you are using energy
    at a rate of 3x the recharge rate. How long do you think you can run
    that motor before you deplete your stored energy capacity? The only
    way it could possibly work would be to allow the I.C.E. generator to
    run even when you were not using the vehicle. So what have you saved?

    Electric motors are really good at only using power as it is required,
    so the whole capacitor thing is pointless anyway. Put a 50HP motor on
    it if you feel it needs 50HP for acceleration, but when it needs only
    20HP to maintain speed, it will only draw power related to that 20HP
    load requirement. The only problem with electric motors is that the
    power it consumes must be carried with it in some form. The batteries
    to carry around enough chemical energy storage for a 250 mile trip
    still weigh too much. Trust me, there are a LOT of people working on
    this issue all the time, and it is not easy to significantly change
    the formula. Hydrogen has promise for the future, but the storage
    issue is still a big hurdle there as well. Solar is quasi-"free", but
    too slow to be practical for transportation. Capacitors can store a
    lot of energy in terms of voltage, but not a lot of net power since
    they will dissipate that voltage relatively quickly. As a point of
    reference, a capacitor bank for a 20HP VFD can hold up the electric
    motor for about 1 cycle, or 16.7 milliseconds when the line power is
    turned off, and weighs approximately 1 pound total. So if you
    extrapolate to your wanting to run the motor for only 7 seconds, it
    would likely weigh 400+ pounds, and what good is 7 seconds going to do
    for you? You still need batteries. Then the energy to recharge that
    capacitor bank is going to be robbed from the charging cycle of the
    batteries, furthering your energy deficit from the little 400cc I.C.E.
    generator.

    Conclusion: In the world of portable power sources, an I.C.E has yet
    to be bested. I do think that the I.C.E. component of the currently
    available hybrid vehicles could probably be improved by being diesel,
    but here in the US we have a lot of environmental concerns associated
    with small diesel engines so it may not be practical at this time. I
    bought a Prius in 2001. I think it is one of the finest examples of
    engineering compromise in human history. I don't get the advertised
    50+ MPG, but I do average 44 MPG fairly consistantly, and coupled with
    an 11.9 gallon tank, I can go a little over 500 miles between
    fill-ups. I doubt anyone can beat that with an all electric vehicle.


    Rant complete. Time to go back to work.
     
  6. daestrom

    daestrom Guest

    Well, I have a different look at it. Yes, finding a place to 'plug in' in
    every parking lot is a problem for sure. But another one is "Why should I
    have to have two different kinds of cars?"

    For the daily commute, an EV would work for a lot of folks. Just park at
    work and plug-in when you get home at night. So the only charger socket one
    needs is in the garage.

    But for long-distance trips, even if every filling station on the interstate
    had a 'socket', who wants to sit around for four to six hours after driving
    for just two?? So, one needs a *different* car for visiting grandma's house
    on Thanksgiving, or spending the weekend at the beach?

    Two different cars, different mechanics, maintenance schedules, parking
    spaces.... Easier to just have one car that does it all. Or if a family
    has to have two cars, it's still easier to have two with the same
    technology.

    daestrom
     
  7. Mike Lamond

    Mike Lamond Guest

    The power pack swap scheme was illustrated on the cover of Popular
    Science sometime in the late 1960's - early 1970's. As I remember it,
    the artist's concept showing the grid assembly being lifted out for
    exchange while the old electrolyte was pumped out so that fresh fluid
    could be pumped in. That sounds like some 1920's auto battery repair
    manuals I've seen.

    An updated version of battery swapping could merge two business
    models that exist now, at least in the U.S.: "15 minute oil change"
    type shops and the propane tank exchange that can be found mostly
    at convenience stores. The drawback is that aging battery packs
    aren't as easily refreshed as propane tanks. Maybe the pack could
    have its own meter showing available kWh, and you would pay for
    the available energy in the fresh pack while receiving some credit
    for the remaining charge in the used pack.

    Mike
     
  8. Bob

    Bob Guest

    Good point, I like your logic. But to address your "charging station"
    issue for commuter cars, I had an all-electric car for a while. I
    commuted to a rapid transit system station in the SF Bay Area
    (B.A.R.T.), and they provide a free plug station at the parking lot
    for EVs. It was great when there were only 5 of us EV users using the
    6 plug stations, but one day I arrived to find them all filled, and
    when I got back to the station that night, I didn't have enough charge
    to get home. In other words, the logistics of even having an EV
    strictly for commuting are very problematic.
     
  9. Bob

    Bob Guest


    OK, instead of focusing on the relatively minor issue of technology
    involved in tracking battery life (and I doubt that it is in any way
    minor), lets look at some quick internet data on the logistics just
    for the US (since that is where I live and have information
    available).

    As of Y2000, there were 195,455 stations where gasoline can be
    purchased. http://sbdcnet.utsa.edu/industry/gas_stations.pdf For
    simplicities sake, lets assume there were 204,000 by 2003.

    Also in the year 2003, there were 204,000,000 gasoline powered
    household vehicles in use in the US, the ones that would be eligible
    for conversion to EV technology.
    http://hypertextbook.com/facts/2001/MarinaStasenko.shtml

    That means each service station must be capable of handling an average
    of 1,000 vehicles (assuming even distribution of course).

    The average number of miles driven in 1998 was 11,725 per year. (same
    NPN report as above). Again, for simplicity, lets even assume we can
    all cut back to 10,000 miles per year (LMAO).

    1,000 vehicles x 10,000 miles/yr = 10 million miles driven by
    customers for each available service station.

    If you can get, lets say, 100 miles out of a battery pack (and that
    would be a stretch), that means each service station must be capable
    of changing out 10,000,000 / 100 = 100,000 battery packs per year!

    Assume we can miraculously design a machine that can change out a set
    of battery packs in 5 minutes, including the time it takes for each
    driver to line up on the "X" (again, LMAO). Another side-splitter:
    getting the industry to standardize on battery packs being universally
    interchangeable! ROFLMAO!

    Let's now also assume that a service station can afford to install 4
    of these machines (big ASSumption), and that each service station runs
    12hrs/day (720 minutes). 4 machines, x 720 mn/day continuously = 2880
    changeout minutes capacity. At 5 minutes per customer = 2880/5 = 576
    customers per day if they are all lined up ready to be charged. 576 x
    365 days = 210,240 customers per year capacity versus the 100,000
    minimum capacity, so that part is doable when you consider the real
    logistics of how people would refuel.

    If each machine cost only $50,000 installed (LMAO again), x 4 machines
    per station, each station would need to invest $100,000 in the
    machines alone. Theoretically doable again, but to make it work, the
    service stations would need to cough it up PRIOR to everyone switching
    to EVs, but lets move on from that side track.

    So as a whole industry, 204,000 stations buying $100,000 worth of
    machines makes this an $20.4 billion dollar investment!

    Now lets not forget the cost of moving and storing 100,000 battery
    packs per year added to that. 100,000 battery packs / 365 days = 274
    packs per day to handle assuming a steady flow. That is roughly 23 /
    hour in that 12 hour day. That's a lot of weight alone, too much to
    expect a person to manhandle, so assume at least 1 fork lift for each
    station, Add another $20,000 investment for each station, bringing it
    up to $120,000, or almost $25 billion in up-front infrastructure
    investment for the service station industry. Not looking so good any
    more as a big picture.

    Now the batteries themselves. 100,000 battery packs need to be used at
    each station per year, which as shown above is 274 packs/day in a 12
    hour sales day. Assume that you only need to actually carry 1/2 of
    those in stock, because you have the other 1/2 being recharged, and it
    takes 1/2 of the day to recharge them (complicated logistics however).
    So now the stations need to buy 137 battery packs. 137 battery packs x
    204,000 stations = 28 MILLION battery packs! Assume, what,
    $500/battery pack? (another laugher because the replacement batteries
    for my Prius are more than that, and they don't need to run the car
    full time) Now you have an overall UP-FRONT battery investment of $14
    BILLION dollars! Makes the machines look relatively insignificant. I
    want into the business of making battery packs!

    So $25 Billion in machine installations plus 14 Billion in batteries
    is now at $39 Billion in infrastrcture.

    Now add to all of this the cost of everyone switching to EVs. ASSume
    you can get the price of a reasonable EV down to $25,000, roughly the
    cost of a Prius right now. 204,000 vehicles x $25,000 / each = another
    $5.1 Billion investment as a society in EVs.

    To all of this we will leave out the cost to society of disposing of
    the gas vehicles, gas tanks at service stations etc. etc., as well as
    the eventual cost of disposing of spent batteries.

    Now consider that the US used $205 Billion worth of gasoline in 2002
    http://www.euromonitor.com/Gasoline_Station_Retailing_in_United_States
    but nearly 1/2 of it was used on commercial trucks, busses and
    motorcycles (NPN study), and so not available as savings by switching
    to EVs. With $110 Billion in annual gas sales being displaced by
    making a $44 Billion investment in EV's and infrastructure, it appears
    to make some sense as a society. But with getting anyone to cough up
    that kind of up-front investment AND suffering the economic impact of
    telling 1/2 the petrochemical industry to just go away, it is not
    likely to happen.
     
  10. Al

    Al Guest

    The same arguement could have been used when horses were replaced by
    automobiles. Substitute hay and oats for gasoline, blacksmith shops for
    gasoline stations, paved roads for lanes, etc. And the pollution from
    the horses could be used as fertilizer not like the pollution from
    autos. I could park my horse in any meadow and it could fill itself up
    while I worked. And, unlike an auto, they were self-replicating.

    ;-)

    Al
     
  11. ehsjr

    ehsjr Guest

    But the analogy is erroneous. Automobiles quickly became
    so vastly superior to the horse that any comparison leaving
    that superiority out is flawed. In the battery vs gasoline
    "debate" the two vehicles are roughly equivalent, with the
    present performance superiority going to the existing technology,
    not the new.

    A battery powered vehicle will have to offer significant
    benefits over the I.C.E., as perceived by the consumer, before
    it replaces existing technology to the same degree that the
    auto has replaced the horse. But it won't be in line with the
    dicsussion which seems to center on relatively "overnight"
    replacement. A phased in approach is more likely, and is in
    fact what is happening. How far it goes remains to be seen.

    Ed
     
  12. Al

    Al Guest

    I'm not disagreeing with you. There are always problems with the
    introduction of new technology. How do you sell pre-recorded tapes to
    people who only have record players? How do you sell CDs to people who
    only have tape recorders? How do you sell DVDs to people who only have
    VCRs?

    My feeling is that we will have to go to all electric eventually. Some
    sort of battery will have to be devised that lasts the life of the
    automobile. My '71 Jag still runs on gasoline 34 yrs later. What will I
    do for batteries 34 yrs later with any battery car I buy? And the source
    will have to be nuclear; anything else is a pipe dream. We have go get
    over our collective consciousness of nuclear danger which was embedded
    into up as kids in the '50s.

    Al
     
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