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Constantly Alternating Between Charging and Re-Gen. on Highway

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by PaulPrius2015, Apr 14, 2015.

  1. PaulPrius2015

    PaulPrius2015 New Member

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    I just bought a 2007 Prius with 140,000 kilometers on it. The car has been regularly serviced at a Toyota dealership according to schedule. My question is, is it normal for the system to continuously switch back and forth between charging the battery and powering the electric motor, while on the highway? I have driven on the highway twice since buying and noticed the system continuously shows arrows running to the battery and then from the battery. This doesn't strike me as an efficient process.
    Thank you,

    Paul
     
    #1 PaulPrius2015, Apr 14, 2015
  2. RobH

    RobH Senior Member

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    Perfectly normal. It's trying to keep the ICE (gas engine) operating at the most efficient speed. When the most efficient ICE speed is higher than needed to move the car, it will charge the battery. If battery usage can allow the ICE to either run at a more efficient speed (or even stop), then it will be used. It's a constant balancing act between required power, required braking, and current battery level. One of the reasons that the Prius gets such good mileage is that the gas engine is kept at the most efficient power level available. Non-hybrid cars have to operate their engines less efficiently. Most of them even run the engine while the car is fully stopped! How crude...
     
    #2 RobH, Apr 14, 2015
    WilDavis likes this.
  3. valde3

    valde3 Senior Member

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    Actually on steady driving at flat highway the power send to or from battery is very small.

    On steady driving at flat highway it changes between two modes.
    -Almost all engine power goes to wheels and just very small fraction is send to battery.
    -Almost all power to wheels comes from the engine just very small fraction comes from the battery.

    So the actual change between is very small. It just looks like big change in the screen.
     
    #3 valde3, Apr 14, 2015
  4. PaulPrius2015

    PaulPrius2015 New Member

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    Hi Rob and Valde,

    Thank you for your responses. I was concerned I may have been facing an expensive repair bill on a recently purchased car. Since I use cruise control on the highway, it's hard for me to get my head around the concept that changes are occurring in the ICE for which the system compensates on a second-by-second basis - ticking back and forth between the 2 modes like a clock. But, your comments help me understand what's actually going on - and that the changes are actually very little.

    Thanks again for your help!

    Sincerely,

    Paul

    P.S. - I am absolutely thrilled with the car. There's nothing I don't like about it and I am very proud to say I am getting an average of 52 MPG!
     
    #4 PaulPrius2015, Apr 14, 2015
  5. WilDavis

    WilDavis Senior Member

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    …it has a lot to do with how heavy your right foot might be! …a good habit might be to pretend you're driving with an (uncooked) egg between your foot and the "Go Pedal", or perhaps removing your shoes and driving in stockinged (or even bare) feet! (…those pedants who yell "…but that's illegal!" are quite welcome to go and boil their heads! It's all about sensitivity! (…check youtube & threads here-abouts for HyperMilers)!
     
    #5 WilDavis, Apr 14, 2015
  6. PaulPrius2015

    PaulPrius2015 New Member

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    Hi Will,

    I totally agree. However, I use cruise control locked at 55 MPH.

    Thanks for your feedback.

    Sincerely,

    Paul
     
    #6 PaulPrius2015, Apr 14, 2015
  7. tanglefoot

    tanglefoot Whee!

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    Although cruise control is efficient on a continuous grade, if the road is hilly at all, it's more efficient to drive with load (DWL) instead, allowing speed to bleed off toward the apex of each hill and then recuperating speed on the downhill side. Cruise control applies too much throttle on the uphills and holds back too much on the downhills.

    The arrows on the MFD are somewhat exaggerated. The gasoline engine does not start and stop nearly as often as the orange arrows indicate. Above about 67 km/h, the gasoline engine always spins.

    Enjoy the Pri!
     
    #7 tanglefoot, Apr 14, 2015
  8. PaulPrius2015

    PaulPrius2015 New Member

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    Thank you for your message. My highway tests were on very smooth, flat highway. Nonetheless, the system constantly switched back and forth, roughly once per second. Though, others have kindly shared with me this is a normal state of affairs for a Prius. I do appreciate your insight.

    Thanks again,

    Paul
     
    #8 PaulPrius2015, Apr 14, 2015
  9. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Where would that be considered illegal? According to these sources, there is no law against that practice.
    Let Your Foot Flag Fly: The Official Ruling on Driving Barefoot - Los Angeles Magazine
    Illegal to Drive Barefoot? - Law and Daily Life
    Is It Legal … To Drive Barefoot? | THELAW.TV

    Being from Honolulu, I commenced that habit when I learned how to drive as a teen, and a few decades later, see no reason to stop.
     
    #9 Patrick Wong, Apr 14, 2015
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