Why doesn't the app indicate 12V battery level?

Discussion in 'Gen 5 Prius Technical Discussion' started by Paul Gregory, Jun 15, 2026 at 3:02 PM.

  1. Paul Gregory

    Paul Gregory Senior Member

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    Since I've moved to my new residence, I've been left with a dead vehicle twice in one week, despite having driven the car the day before. I have a battery maintainer, but no way to plug it in. I am frequently faced with an inoperable vehicle due to "battery level too low," requiring a boost.

    Of course the stupid reply is always: "replace the battery" or "fix the parasitic drain." But both those avenues have been exhaustively pursued, hence the battery maintainer (and the boost-pack).

    This is a serious flaw with my Prius Prime. The battery can run down to a level which disables the car, sometimes within a few hours. A way to check the battery level from the app would be a helpful start.
     
  2. Brian1954

    Brian1954 Senior Member

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    I assume you are talking about the Toyota app that connects to the car. I agree that a look at the actual 12v battery voltage would be a nice feature. Any questions about why it is not included in the app would need to be directed to Toyota. Maybe if enough people ask for it, Toyota will include it in the future.
     
  3. bisco

    bisco cookie crumbler

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  4. Hammersmith

    Hammersmith Senior Member

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    So, you want hardware and software running all the time to monitor battery state and communicate that info to the Toyota servers using the data communication module? And this is because you're concerned about the car using too much power when it's not in use?

    Does anyone else see the inherent problem with this idea?


    OP: Just have your battery tested again so that they'll tell you it's bad, you'll get a replacement under warranty, and we can put this to bed for a few months. Please?
     
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  5. Paul Gregory

    Paul Gregory Senior Member

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    It doesn't seem to matter how many times I say that the battery has been replaced,
    the same stupid suggestions keep coming.

    I hate when the battery goes completely dead, requiring me to spend considerable time resetting everything.
     
  6. LRO

    LRO Junior Member

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    If the idea is to know in advance whether the battery level is too low to do anything perhaps using the Toyota app might work as is.

    At the bottom of the "Status" tab it'll indicate how many minutes since the data has been updated. If not current, you can then pull down on your screen or click the refresh icon and that'll command Toyota to communicate with your vehicle and grab the latest data.

    Seeing anything other than just now or less than a minute ago but rather an "Updated: x minutes ago" that only climbs might be indicative of boost-pack time again.

    And as @Hammersmith indicates there's a cost to your 12-volt battery just doing these refreshes and not something you'd want to just do over and over in a single session. Somehow I think Toyota knows this or has agreements with mobile carriers to perhaps limit the number of times one can refresh in a given period of time.
     
  7. Paul Gregory

    Paul Gregory Senior Member

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    It doesn't seem like much of an engineering challenge; if the hybrid battery has a sufficient charge, it should activate the power converter when the start button is pressed, restoring power to the 12V system.
    It's always been a bit stupid for the car to become dead in the water, while many kilowatts of power exists in the hybrid battery.
     
  8. Paul Gregory

    Paul Gregory Senior Member

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    It appears that all the functions of the app still operate while the battery voltage is too low to start the vehicle.
     
  9. Brian1954

    Brian1954 Senior Member

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    The Toyota app does not work like you described. Forcing a refresh at the bottom of the status screen does not "command Toyota to communicate with your vehicle and grab the latest data". The refresh only causes your Toyota app to connect to the server and refreshes the data on your app from the data on the server. It does not force a connection from the server to the car to grab the latest data from the car.

    You may ask, how I know this. I have the Toyota app connected to my 2026 Toyota. On the status page, I see the diagram of the car showing the four tire pressures. Just below that, it says,
    Tire Pressure
    it shows a blue check mark and Good
    Updated 19 hours ago

    The information on the status page does not change when I force a refresh at the bottom of the status page.

    So, the Toyota app can not be used to force a connection between the car and the server. The app can not be used in the way you described to check to see if the 12v battery level is too low to do anything.
     
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  10. Brian1954

    Brian1954 Senior Member

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    You are correct. See my post #9 for an explanation.
     
  11. LRO

    LRO Junior Member

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    Yes, I agree with you about the tire pressures not updating when refreshing the app as those TPMS sensors only wake up when the wheels physically move to preserve the battery in each sensor and even then their tiny batteries probably throttle their updates less often than right this minute. But still kind of know from my own experience that other stale data in the app is updated after Toyota reaches out and consults the vehicle ... door locks, windows are kind of important to know the status of remotely at times and perhaps even the HV/Traction battery charge level.