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Strange HV battery behavior?

Discussion in 'Prime Plug-in Charging' started by Kragzakh, Jan 31, 2024.

  1. Kragzakh

    Kragzakh Junior Member

    Joined:
    May 31, 2018
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    Location:
    Boston, MA
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Curious if anyone here has seen similar behavior and if so what was the problem/how did you resolve it?

    I don’t drive the car a lot anymore - it’s a 2017 with 47k miles on it. But I do take it out at least once per week for grocery shopping. Most of my trips are 100% EV so I didn’t notice is new behavior until I took it on a longer drive that depleted the EV battery.

    In early Nov I took said longer drive and when I parked the car the HV battery indicator was full while the EV battery had been depleted. It was parked in a parking garage on a mid-60 degree day. When I returned to the car approximately 1hr later, the moment I pressed the start button the ICE kicked on and I noticed the HV indicator was almost empty. It charged back up to full in about 3-4 minutes of driving. And the car behaved normally after that. Since movement I’ve had this same thing happen during a visit to a store that was less than 15 minutes. HV indicator full when I go in the store, <15 mins later, I come out, start the car and the HV indicator is almost empty and the ICE starts up to charge it.

    Since that time i have had the same experience 8 or more times. I even watched it happen while driving on the highway recently. Was in EV mode, and I watched as the as the car switched from EV to HV mode and the HV portion of the gauge which was reading full, quickly dropped to almost empty. I wish I’d gotten a video of it.

    I did also have the 12V battery die and needed a jump 2x in that same timeframe, I’ve since replaced the 12v battery. I originally thought the 2 issues were unrelated, but some comments I’ve received on Facebook have confused the issue for me and now I’m not sure if they’re potentially related or not.

    I’ve since looked at things with Dr. Prius but I have no idea what I’m looking at. I have noticed that when this happens the 12V battery voltage is typically >14V so the argument (from Facebook) that even the new battery is the problem and the ICE is kicking in to charge THAT battery is questionable IMO.

    Does anyone have any ideas what’s going on, or what I should tell the dealer to check? I’ve already had it to the dealer once and they couldn’t find any issues.
     
    #1 Kragzakh, Jan 31, 2024
  2. Kragzakh

    Kragzakh Junior Member

    Joined:
    May 31, 2018
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    Vehicle:
    2017 Prius Prime
    Model:
    Prime Advanced
    Here is a video of this occurring.

     
    #2 Kragzakh, Jan 31, 2024
  3. bisco

    bisco cookie crumbler

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    Plug-in Base
    Has it happened since replacing the 12 volt?
     
    #3 bisco, Jan 31, 2024
  4. Kragzakh

    Kragzakh Junior Member

    Joined:
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    2017 Prius Prime
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    Prime Advanced
    Yes it continues to happen since replacing the 12V.
     
    #4 Kragzakh, Jan 31, 2024
  5. bisco

    bisco cookie crumbler

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    Plug-in Base
    i don't think i've ever seen this before. it is fortunate that you can duplicate it for the dealer.
     
    #5 bisco, Jan 31, 2024
  6. vvillovv

    vvillovv Senior Member

    Joined:
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    Location:
    NY
    Vehicle:
    2017 Prius Prime
    Model:
    Prime Plus
    Three things I've noticed ( be that what it may );
    - First the HV battery portion of the HV battery is a conceptual thing, it's not a real thing in terms of the HV battery s voltage and that can be seen using the DrPrius / DrHtybrid app.
    - The 14 volts shown in DrPrius / DrHybrid app is a reading taken from ODB11 ports reported voltage AND doesn't necessarily always show what is happening at the 12 volt batteries terminals. This can be gleemed by using the Car Scanner app which show 2 12 volt sensors in the All Sensor section of the app AND also by using a multimeter on the 12 volt battery terminals while watching the app, at different times in different modes, etc..
    - I've detected a kind of partial reset thing going on after the Prime is turned OFF. ( I got blowback from other Prime owner(s) here at priuschat a few years ago ) that told me I was crazy or seeing things that weren't really happening.
    For me I'd drive on the same route many times without much traffic or other distractions, measuring how far I could drive in EV mode and make it back home without having the engine start. Longer story shortened a lot ( ... ) several times I'd stop with some EV range left and 2 or 3 tenths of a mile back to a charger and close to 3 miles up about 300 ft in elevation to home. ( this partial reset thing is only noticeable with very little EV range showing .
    1 mile of EV range might be too much to show the EV range reset, I never tested how much EV range was where this reset thing stopped showing up on the gauge ).
    After shutting off the Prime with nearly double the range needed to get back to the charger 2 or 3 tenths of a mile away, when I got back to the car ( ten minutes later, max ) I noticed I no longer had that same ( almost double the EV range needed to get back to the charger 2 or 3 tenths of a mile away / back ). And sure enough the engine would start before I made it to the charger sometimes other times I could glide into the charger space by using ( limp mode at under 5 mph) .
    It wasn't a big issue for me and I didn't feel like bucking na sayers while testing multiple other things about the Prime, so I only noted it and posted about it one other time..
     
    #6 vvillovv, Feb 1, 2024
    Last edited: Feb 1, 2024
  7. sylvaing

    sylvaing Senior Member

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    Vehicle:
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    Plug-in Base
    This is a great video to watch to get an idea on how the 12V charging of the Gen 4 Prius works.

     
    #7 sylvaing, Feb 1, 2024
    Kragzakh likes this.
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