Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Electric cars

  1. Jan 30, 2008 #1
    Anyone with any idea about the basic internal design & engines in an electric car?
     
  2. jcsd
  3. Jan 30, 2008 #2

    berkeman

    User Avatar

    Staff: Mentor

    What research have you done so far? What do you know about the subject? If you have specific questions, that would be easier for us to address. Start by reading some background material:

    http://en.wikipedia.org/wiki/Electric_car
     
  4. Jan 30, 2008 #3

    chroot

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Electric cars don't have engines, they have motors. Try asking more specific questions.

    - Warren
     
  5. Jan 31, 2008 #4
    Well the basic components are batteries, a controller, and an AC or DC electric motor. Batteries are usually Lead Acid, but more recently NiMH or Lithium. The controller varies only the current to the motor. Voltages are over 100V. Motors are usually adapted DC or AC industrial process motors. Some can do 1/4 miles in under 10 seconds, but I doubt they have much range. The Chevy Volt uses lithium batteries with an AC motor.
     
  6. Feb 4, 2008 #5

    mheslep

    User Avatar
    Gold Member

    I read somewhere that Chevy would not go to full production on the volt unless they could get the price down on batteries, the Li ion technology is apparently still too expensive. Anyone corroborate?
     
  7. Feb 4, 2008 #6
    Yes, thats right. There is a tour of the developement centre in a magazine a just got. Basically, there are 2 major companies competing for the battery contract. They said it was difficult to develop it backwards compared to a normal car since the whole car will be ready before the power plant is developed. This way the car will launch as soon as the technology is available, and they will be the first to have a Li ion car on the road. They plan to lose money on during the first few years that they sell the Chevy Volt. Its more about building an image.
     
  8. Feb 5, 2008 #7

    mheslep

    User Avatar
    Gold Member

    Hmm. Usually car makers require a component to be tested out to half its expected life before it hits the assem. line. Thus a 10yr life battery system would be expected to run in the lab for 5yrs, or under some kind of accelerated environment that simulates that period. If they follow procedure they're still ~5 yrs away.
     
  9. Feb 5, 2008 #8

    mheslep

    User Avatar
    Gold Member

    A123 and Valence?
     
  10. Feb 5, 2008 #9

    RonL

    User Avatar
    Gold Member

    I have a hard time accepting that auto designers can't produce a design that gives us what is needed by 80+ % of the population, it seems that perfection and efficiency are sought after to the extent we price ourselves out of what we want.
    Putting together a lead acid system should be possible, that can produce 150 or so miles per day, with 75% or more of the total weight below the center of gravity, rollovers would be almost eliminated, and the battery system could be enclosed to such extent, that an accident would involve no more than replacement of wheels, and maybe the body.
    Batteries can be designed with the intent of servicing them, the extra weight can be used to other advantages.
    IMHO the lead acid battery still has a few design changes, that can be made, that will invoke the question "why didn't we think of that sooner?":uhh:
     
    Last edited: Feb 5, 2008
  11. Feb 5, 2008 #10

    mheslep

    User Avatar
    Gold Member

    No its not economically possible. Lead acid has about 1/10 the energy density (kilowatt-hrs/kg) of Lithium ion. The extra weight is not a benign problem of mass distribution. More weight requires more power to accelerate it which requires more batteries and so on. For example, the Li-ion batteries on the Chevy Volt are now just enough to travel 40miles - commuter range. The batteries appear to take up about one M^3 and about ~300lbs(?) if I recall. Replacing that w/ lead acid would take 10X the battery weight alone; such a car is not going anywhere.
     
  12. Feb 5, 2008 #11

    RonL

    User Avatar
    Gold Member

    I do need to extend an apology to the engineering group, as i tend to forget about the safety, and foolproof design they have to comply with. (a very nice looking car)
    Do you have any cost comparisons between the batteries? a little over two years ago i purchased twelve 12 volt deep cycle marine batteries, 100 Ah each, their weight is a little over 750 pounds, and after tax my cost about 850.00 US. The project fell apart and i have used them from time to time in other ways, and hope to put them in service before the summer heat is on, in an attempt to store some solar energy for my home. I have every thing except a nice solar panel to set up a pretty good system.
    I have gotten as much as 6-7 years service, on some of my heavy equipment batteries, and i believe some of the negative press of lead acid comes from, people spending too little and expecting too much.
    Because i tend to ramble, maybe i should start a blog.:zzz:

    Thanks for your answer, and the reference to the Volt. My guess is it will sale for more than 60,000$ ?? Oh well its our future trend:smile:
     
  13. Feb 5, 2008 #12

    mheslep

    User Avatar
    Gold Member

    Lithium Batteries Take to the Road Sept 2007
    (maybe subscription only)
    A commuter car needs 12KWh, very roughly.

    Then thats not from deep cycles, must be pulse operation (starting cars) or idling for backup. Deep cycle those lead acid's many times and they are done, time for another $800.
     
    Last edited: Feb 6, 2008
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?