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Generally High SOC, Battery Charging Uphill with "Green" SOC

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by J Skyler, Feb 20, 2013.

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  1. J Skyler

    J Skyler Junior Member

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    Alright guys, I did the mileage test and here are my results:
    First leg, 5 miles, slight downhill, 79.9 mpg
    Second leg, 5 miles back the way I came, 40.7

    Which averages to 60.3. Maybe there was some energy that I recaptured doing the downhill first, but the run was 5 to 10 minutes into the trip, and testing lasted 25 minutes. It seems like the car's alright.

    I still find it weird that the battery is green so much, but it looks like its more to do with the driver than the car.

    Thanks for all the help.

    Skyler
     
    #21 J Skyler, Mar 2, 2013
  2. edthefox5

    edthefox5 Senior Member

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    Car sounds fine but you can't do the test on an incline. Has to be a flat highway. One way is all you need about 5 miles. Start off in cc and reset the meter. At the end of the run all the consumption blocks should be even and very few turtles (greencars on the blocks representing charging). At 55 mph's in cc for 5 miles you should have around 52 mpg's and the battery should be all blue not green.
     
    #22 edthefox5, Mar 2, 2013
  3. J Skyler

    J Skyler Junior Member

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    Unfortunately that test will have to wait a little while. I live in a hilly area, and driving 30 minutes to get to a flat section of highway is not going to happen soon. Why do you discount my averaging going down and then back up so readily? It seems like if anything I should have gotten worse average mileage due to energy losses, not better.
     
    #23 J Skyler, Mar 2, 2013
  4. edthefox5

    edthefox5 Senior Member

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    Because I know what this exact test should reveal or real close to it. Trying to help you. If your satisfied with your test that's great. Proceed.
     
    #24 edthefox5, Mar 2, 2013
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I agree that the car is alright. However please note that to compute your average fuel economy, you cannot take the average of the two mpg readings.

    Rather, you need to compute your fuel consumption (how much gasoline was used) for each leg of the trip. Then add the two fuel consumption numbers together.

    mpg computation for the round trip = (total distance roundtrip) / (total fuel consumption).

    Given the mpg cited by you for each leg of the trip, it appears that your car consumed 0.185 gallons of fuel over 10 miles. Hence I believe your car registered 53.9 mpg for the roundtrip which is quite good and higher than Ed's metric. This is subject to the accuracy of the MFD mpg gauge.
     
    #25 Patrick Wong, Mar 2, 2013
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  6. J Skyler

    J Skyler Junior Member

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    Ed,

    I didn't mean to sound defensive, and I'm sorry that I did. I was genuinely curious why averaging the mpg's wouldn't work.

    Thanks Patrick. I think I understand my error of averaging two inverse rates of consumption, vs. the actual consumption. Interestingly, if I average the inverse of 79.9 and 40.7, then invert it again I come up with 53.93, or your number.

    Again, thanks for all your help gentlemen. I appreciate your patience with a new driver.

    -Skyler
     
    #26 J Skyler, Mar 5, 2013
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  7. edthefox5

    edthefox5 Senior Member

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    No problem sorry if I sounded snippy but I truly meant I was Trying to help you but if your ok thats ok.
     
    #27 edthefox5, Mar 5, 2013
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes - here's an extreme example, worthy of becoming a question on the high school Math SAT exam:

    You are towing a very heavy load uphill and get 1 mpg on that trip. Then you unload, coast in neutral downhill, and get 100 mpg on the return trip.

    What is the average mpg for the round trip? Some might say 50.5 mpg.

    However, the correct answer is 1.98 mpg.

    The European and Japanese metric of Liter/100 kilometers is better because it focuses on how much fuel is consumed for a fixed distance (instead of how far you can drive on a gallon.) You can average your L/100 km results for the two legs of a round trip, without error.
     
    #28 Patrick Wong, Mar 5, 2013
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