ICE cycles on and off rapidly with car at a stop

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by unmesh59, May 25, 2013.

  1. unmesh59

    unmesh59 Junior Member

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    I was driving down a stretch of freeway that sloped down, took an exit, and rolled to a stop at a red light. The traction battery indicator was at full. While waiting for the light to turn green, the ICE would come on for a few seconds, turn off for a few seconds, turn on again, doing so for the minute or so until we started moving again.

    No one has reported it on this thread that I'm aware of and I'm hoping someone has thoughts on what was happening.

    Thanks.
     
    #1 unmesh59, May 25, 2013
  2. jdcollins5

    jdcollins5 Senior Member

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    The HV battery SOC was high after the downgrade and regen so the ICE was spinning to burn off the excess charge. Completely normal.
     
    #2 jdcollins5, May 25, 2013
  3. nh7o

    nh7o Off grid since 1980

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    It sounds like the system was running the engine as a load to reduce the charge on the HV battery. When the battery is quite full, there is an exothermic reaction that is detrimental to the cells, and the system will try to "blow off some steam" as it were. The B mode is the same (engine braking mode), and spins the engine to provide additional braking after the regen system has topped off the battery. The car switches to B mode automatically if needed, although in places where I know I will be going downhill for a long time, I switch to B mode proactively.
     
    #3 nh7o, May 25, 2013
  4. unmesh59

    unmesh59 Junior Member

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    128K miles and this is the first time I've seen this happen!

    Thanks, guys.
     
    #4 unmesh59, May 25, 2013
  5. nh7o

    nh7o Off grid since 1980

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    There are some surprises that happen when watching the SOC meter. Things happen one day differently from the next, in my experience. The HV battery ECU run some complex management cycles, from the looks of it.
     
    #5 nh7o, May 25, 2013
  6. edthefox5

    edthefox5 Senior Member

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    Absolute best time to clean the brakes. Brake on & off all the way down in neutral. Wish I had a few hills around here.
     
    #6 edthefox5, May 25, 2013
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