Prius not switching into EV mode - 12v battery

Discussion in 'Prius c Care, Maintenance and Troubleshooting' started by Meditation, Apr 16, 2017.

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  1. Meditation

    Meditation Junior Member

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    I have a 14' C, 3 years old, has 63K on it. I use the car for local commercial driving so ~40-55 miles/day 8:30am to about 3PM, it idles a bit too since I'll park for ~10-30 mins between trips w/ the ac on low. I've noticed in the afternoon around noon the car does not like to switch into EV mode unless it's below 22MPH. normally the car will go ev under ~42MPH. I also notice the throttle from a stop light the car will be quicker to turn the engine on then using the EV acceleration. here is a video I took coasting downhill in the afternoon to demonstrate the problem:



    later that same day I came home parked the car for 2 hours, then drove to the gym. on the way there and back it seemed the engine was running a lot, even when I was cruising around 10-20MPH the engine stayed on :notworthy:

    I sprayed the throttle intake with CRC Twice, didn't make any difference. I also checked the vent under the passenger seat and it's clear.

    Does this seem like it's a 12V battery issue? What tool(s) can I buy to use to test the voltage?
     
    #1 Meditation, Apr 16, 2017
  2. TheTimob

    TheTimob Member

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    My car has done this a few times. I think it might be some sort of test program - it does weird things like drains the battery down very low or fills it up all the way.

    It also could be a hot HV battery. Was the battery fan running hard?
     
    #2 TheTimob, Apr 16, 2017
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  3. bisco

    bisco cookie crumbler

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    what the outside temp? doesn't seem like a 12v issue. do you carry any animals?
     
    #3 bisco, Apr 16, 2017
  4. Meditation

    Meditation Junior Member

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    I've seen it do the the idle & fill the battery bars few times, but mostly infrequently. How do I know if the battery fan is running hard? I use the AC on low or the 2-3 from low. that something I can hear from the hood or rear?

    outside temp in the afternoon is around ~75-85° lately . no animals ever.

    my MPG in the morning is around ~50-60. In the afternoon it's like ~38-45 so a significant difference even though i'm mostly driving local. I also notice if I'm going around 50-60MPH and I let off the throttle it seems to rev itself up for second? is that normal? could it be transmission issue?
     
    #4 Meditation, Apr 17, 2017
    Last edited: Apr 17, 2017
  5. bisco

    bisco cookie crumbler

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    seems more like a battery issue. is the battery charge display acting abnormally in any way? it might be worth having a look at the cooling fan.
     
    #5 bisco, Apr 17, 2017
  6. Sam Spade

    Sam Spade Senior Member

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    Except for coasting and stopping, I have NEVER been able to coax my C into EV mode above about 22 MPH.......and I think it is pretty much designed that way.

    And it does do some "strange" things with running the engine at times, but that doesn't last long and then everything goes back to "normal".

    If other strange things start happening you might suspect the 12 V battery......but not now.
     
    #6 Sam Spade, Apr 17, 2017
  7. Gasoholic

    Gasoholic Junior Member

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    If you let off the gas completely, it should shift to EV mode, unless the throttle position is too depressed to allow it. My 2016 C 3 will enter EV with this method, below 40 mph.
    Gasoholic
     
    #7 Gasoholic, Apr 17, 2017
  8. Sean Nelson

    Sean Nelson Active Member

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    That's only true if the vehicle control computer doesn't have some other reason for keeping the engine running, such as during the warm-up phase or if you're asking for a lot of heat and the coolant isn't hot enough to provide it.
     
    #8 Sean Nelson, Apr 17, 2017
  9. Red-

    Red- New Member

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    I have the exact same problem with my 2013 Aqua (aka prius c in Japan). The engine blips the throttle when I let go of it, keeps on running even if I'm at a stop light.. This is usually if I've ran the car a bit fast.. Usually it's hard to keep it in EV. I am assuming the cooling fan is not working...? because I have no blockages at the vent. My 12v battery is giving out 12 1/2 volts after not being used over night. The temperature here currently is 113F.
     
    #9 Red-, Apr 18, 2017
  10. Sam Spade

    Sam Spade Senior Member

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    Well you can keep worrying about that if you MUST but I am telling you that IF it only exhibits that unusual behavior occasionally......or after a triggering event like driving like you stole it.......that does NOT indicate a problem.

    And the design of the C makes it hard to "keep it in EV" with driver actions.
    That's just the way it IS.
     
    #10 Sam Spade, Apr 18, 2017
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  11. Meditation

    Meditation Junior Member

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    Battery charging is normal, it fills up and drains as I use EV power. When I idle the car w/ AC it switches on and off normal.

    After looking around more I think it may be the battery cooling fan, I do idle it like 1-1.5 hour/day so it may be dirty. Are there any tutorial vids on how to inspect/clean the battery cooling fan specifc for a C? The tutorials for the lift back look daunting o_O I'm going to blow compressed air into the vents with the car off see if this helps first.
     
    #11 Meditation, Apr 19, 2017
  12. bisco

    bisco cookie crumbler

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    not that i know of. google you tube to see if anyone has done anything on it.
     
    #12 bisco, Apr 19, 2017
  13. Meditation

    Meditation Junior Member

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    What is the replacement frequency or expected lifespan for the 12v battery?
     
    #13 Meditation, May 8, 2017
  14. Sam Spade

    Sam Spade Senior Member

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    If it has not been abused by running it totally flat......the sealed AGMs should have a life of at least 5 years; maybe a bit less in a REALLY HOT environment.

    One with caps to add water, maybe 3-4 years......IF you add water as needed.
     
    #14 Sam Spade, May 9, 2017
  15. Sean Nelson

    Sean Nelson Active Member

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    The original 12V battery on my 2012 Prius C is still working just fine, although I'm thinking of replacing it just because of it's age.
     
    #15 Sean Nelson, May 9, 2017
  16. Meditation

    Meditation Junior Member

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    Had the 65K done 5/11/17. I had them clean the HV fan. My mechanic was skeptical, said if the fan is not working properly it will throw a code. They cleaned it for $85, said the fan had lots of lint.

    The prius is now driving normal and actually feels lot faster now, it gives EV mode all day now, EV motor seems more responsive, engine comes on less. I'm back to getting 60+MPG on local roads like usual :)

    My theory -as the car is driven the battery will increasingly heat up, with the HV fan working only 50-70% effective at some point a portion of the battery or all of it be too warm to use so it runs the engine to force more air. seems why I was only able to activate it at 22MPH or lower.
     
    #16 Meditation, May 16, 2017
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  17. Sam Spade

    Sam Spade Senior Member

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    I have told you this before (I think) and now once again:
    That is the way the C is designed.
    I have a brand new '17 with less than 500 miles and it does that too.......just like the last one I had that acted like that for about 35,000 miles.
    IT IS NORMAL BEHAVIOR.
    The EV button is mostly worthless.
     
    #17 Sam Spade, May 16, 2017
  18. Meditation

    Meditation Junior Member

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    I never use the EV button, just keep it in eco mode and and use the throttle for EV.

    it now cycles more quickly through stages, so more EV time :)
     
    #18 Meditation, May 17, 2017
  19. Sam Spade

    Sam Spade Senior Member

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    Good. I'm glad that you are happier now. (y)

    (Note: are you familiar with the placebo effect ??) :whistle:
     
    #19 Sam Spade, May 17, 2017
  20. Former Member 68813

    Former Member 68813 Senior Member

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    are you always such a jerk?
     
    #20 Former Member 68813, May 17, 2017
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