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AC on is Running The Battery Down

Discussion in 'Gen 3 Prius Care, Maintenance & Troubleshooting' started by Eddie Brown, Jul 17, 2013.

  1. Eddie Brown

    Eddie Brown Junior Member

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    Lately when I turn the AC on my battery runs all the way down to two purple bars. The temp here is hot and it happens when I'm traveling at low speeds. The battery finally gets back up once I drive faster.

    Is this normal or is there something I should be doing to prevent this?
     
    #1 Eddie Brown, Jul 17, 2013
  2. Paradox

    Paradox Prius Enthusiast / Moderator
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    Normal, the A/C is driven off the battery at low speeds and when the battery gets low enough the engine must run to keep the battery at proper operating levels. It goes up once driving at normal speeds because that also causes the engine to run charging the battery back up.

    Basically, the car manages the battery and the gauge for it doesn't need much attention.
     
    #2 Paradox, Jul 17, 2013
  3. Bill the Engineer

    Bill the Engineer Senior Member

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    Very normal. My 2004 does it whenever it is 90deg or higher, especially when I am waiting in a drive-thru line.
     
    #3 Bill the Engineer, Jul 17, 2013
  4. rdgrimes

    rdgrimes Senior Member

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    It really helps, when you're stopped, to just reach over and hit the A/C button, leaving the blower on in recirc mode. I can usually tolerate that for the minute or so it takes for the light to change. Saves a bit of juice and I notice it on the battery guage.
     
    #4 rdgrimes, Jul 17, 2013
  5. MikeDee

    MikeDee Senior Member

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    Eco mode might help.

    Galaxy Nexus ? 2
     
    #5 MikeDee, Jul 18, 2013
  6. jdcollins5

    jdcollins5 Senior Member

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    Keep in mind that the AC is used to help cool the HV batteries. So it is best to leave the AC on in hot temps and let the computers take care of the HV batteries.
     
    #6 jdcollins5, Jul 18, 2013
  7. retired4999

    retired4999 Prius driver since 2005

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    Yes, I think if in eco mode it will turn off the ac compressor at stop signs and lights and start again when you start off.
    Please correct me if I'm wrong.
     
    #7 retired4999, Jul 18, 2013
  8. rdgrimes

    rdgrimes Senior Member

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    You're wrong. :p

    What it does is make the compressor run less ALL the time, giving you slightly warmer air from the vents, and it lowers the blower speed all the time as well.
     
    #8 rdgrimes, Jul 18, 2013
  9. jdcollins5

    jdcollins5 Senior Member

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    ECO mode also takes a LOT longer to cool the cabin temp down in hot weather. In hot weather I would certainly let the AC cool the cabin temp down to a comfortable level before switching to ECO if you are like me and more concerned with HV battery health than mpg.
     
    #9 jdcollins5, Jul 19, 2013
  10. rdgrimes

    rdgrimes Senior Member

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    ECO mode A/C control also only works when the HVAC system is in Auto mode.
     
    #10 rdgrimes, Jul 19, 2013
  11. css28

    css28 Senior Member

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    I recommend sitting out stage 1a before getting the car underway. That way you can drive the wheels from the engine instead of just the battery and the generator has a chance to get ahead a little bit.
     
    #11 css28, Jul 19, 2013
  12. retired4999

    retired4999 Prius driver since 2005

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    Thanks!
     
    #12 retired4999, Jul 19, 2013
  13. retired4999

    retired4999 Prius driver since 2005

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    From the Toyota manual.■Operation of the air conditioning system in Eco drive mode
    In the Eco drive mode, the air conditioning system is controlled as follows to
    prioritize fuel efficiency:
    ●Engine speed and compressor operation controlled to restrict heating/
    cooling capacity
    ●Fan speed restricted when automatic mode is selected.
     
    #13 retired4999, Jul 19, 2013
  14. rdgrimes

    rdgrimes Senior Member

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    If you read the fine print, you'll also see about how this is only true in "auto" HVAC mode. As soon as you adjust fan speed manually you lose auto mode and ECO HVAC mode status.
     
    #14 rdgrimes, Jul 19, 2013
  15. retired4999

    retired4999 Prius driver since 2005

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    I understand that. Thanks. If you can't get cool enough by decreasing the temp. Just put in manual and adjust to your needs. I have always gotten cool in 95 degree heat but thats just me, YMMV! :) Cooler here than down south!
     
    #15 retired4999, Jul 19, 2013
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