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Re: [force_ev] RE: My Mileage varies

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  • umarc@hippogryph.com
    ... I do notice that coasting down hills I don t recover as many amp-hours when it s cold. Also, my car whines when it s cold. When I get up to 30 mph or so,
    Message 1 of 3 , Feb 25, 2002
      On Fri, 22 Feb 2002, Tracy, Matt wrote:

      > Other factors for mileage include air density, colder air is thicker, so it
      > takes more work to push through it; tire temperature, warmer tires generally
      > have lower hysteresis (sp?) losses (the work to change the tire from round
      > to flat and back to round as it revolves); and the pavement itself has
      > different "stickiness" characteristics with changing temperature.

      I do notice that coasting down hills I don't recover as many amp-hours
      when it's cold.

      Also, my car whines when it's cold. When I get up to 30 mph or so, I'll
      hear a musical note somewhere between 500 Hz and 1,000 Hz, which will die
      away if I go eiher faster or slower. It seems to be some sort of
      mechanical resonance, and the actual speed at which I hear it varies with
      temperature. If the temperature is in the high thirties or above I don't
      hear it at all.

      > And if you are driving through an inch of snow, that increases work
      > expended, also (be aware, this one can be pretty significant - also
      > applies to sand or other soft surfaces).

      My car performs so poorly in snow that I've found it best not to drive it
      if there's any snow on the roads.

      > All that is in addition to any loss of efficiency
      > from the batteries due to less than optimal temperature (not too hot, not
      > too cold, juuuust right).

      The Solectria manual warned me that it isn't a good idea to discharge the
      batteries deeply as a habit, but it didn't tell me how drastically the
      definition of "deep discharge" changes when it gets cold outside. Last
      winter I was driving 20+ miles between charges almost every day, and I
      think that may be why I only got a year out of my first set of batteries.

      This winter my employer has given me permission to charge at work, so I've
      never had to go more than 10 miles between charges. I hope this will
      translate into longer battery life.

      Rob Landry
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