Accessory Mode and Battery Shut Down

Discussion in 'Prime Main Forum (2017-2022)' started by stevepea, May 30, 2017.

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  1. stevepea

    stevepea Senior Member

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    One thing I noticed the other day was the quirks the Prime has when the car is parked and just in Accessory mode (if you're hanging out in a parking lot for a while waiting for someone, and want to listen to the radio, for instance).

    First, everything shuts off after a while (the radio, everything -- even when it's on and you're listening to it) with a message displayed that to prevent battery drain, everything is being turned off. Does the Prime have a normal/separate 12V battery for accessories (different than the main EV powertrain battery?) If so, I've had no other car I know of shut everything off like this. I don't remember the time period before shutoff (probably at least 10-15 mins) but when I rebooted the car and turned everything back on, cycling back to Accessory again to keep listening, the same thing happened again a while later.

    Second (perhaps just a quirk with Priuses in general? don't know) you cannot run just the fan (not talking about A/C or heat, just the fan) or even the windows while out of ready-to-drive mode, (ie, in Accessories mode). Windows you can sometimes use for about a minute or so after shutting the engine off, but after a minute or so, you can no longer operate the windows again without pressing the POWER button to leave Accessories mode and enter driving mode. And with the fan (if you just want a fan blowing, even outside air, with no heating or cooling), that's not possible at all in Accessories mode it seems.

    Is there a way you can turn off the automatic shutoff of everything after a few minutes in Accessory mode?

    One cannot run any audio for a long period of time (or just the fan for any period of time) if not in the ready-to-drive mode, it seems.
     
    #1 stevepea, May 30, 2017
  2. Lee Jay

    Lee Jay Senior Member

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    It's supposed to shut off after 20 minutes. Because of a bug in the software, it never lasts that long and the amount of time it does last is quite random. Sometime it lasts 45 seconds, sometimes a few minutes.
     
    #2 Lee Jay, May 30, 2017
  3. alexcue

    alexcue Active Member

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    20 minutes is all it's supposed to be. I've never timed it, but it's to protect the 12v battery from draining.

    The minute to move the windows after shut down is pretty standard in Toyota's as far as I know. My 2002 Tundra does the same thing, till a door is opened then I'm screwed. The GF has learned to wait till we drop the windows a tad in the summer before she opens the door, otherwise I had to turn the ignition on every time to lower the windows.
     
    #3 alexcue, May 30, 2017
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  4. bisco

    bisco cookie crumbler

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    just leave it in ready.
     
    #4 bisco, May 30, 2017
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  5. Prius from Dad

    Prius from Dad Senior Member

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    Unless no EV left.
     
    #5 Prius from Dad, May 30, 2017
  6. Washingtonian

    Washingtonian Senior Member

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    Ready with the parking brake on seems safe. Will it consume a significant amount of power in that mode compared to Accessory?
     
    #6 Washingtonian, May 30, 2017
  7. bisco

    bisco cookie crumbler

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    no, very little, but the hybrid battery will keep the 12v charged, and when the hybrid battery goes down to a certain point, the engine will come on to charge the hybrid battery. or if you have some wall charge, the engine won't run at all, until it's gone.
     
    #7 bisco, May 30, 2017
  8. Prius from Dad

    Prius from Dad Senior Member

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    Ready mode will use the traction battery, ACC mode uses the 12 volt battery just like a regular car.
     
    #8 Prius from Dad, May 30, 2017
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  9. Jeremy Greenwood

    Jeremy Greenwood New Member

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    I had it auto shut down during an app update for entune setup. Was not happy with the lack of user permission or override due to a seeming software install process. Nonetheless download and install picked up next time u started it. It was about 20 but didn't time.

    Posted via the PriusChat mobile app.
     
    #9 Jeremy Greenwood, May 30, 2017
  10. bisco

    bisco cookie crumbler

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    good to hear there's a fix.
     
    #10 bisco, May 30, 2017
  11. CharlesH

    CharlesH CA HOV Decal #5 on former PiP

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    And yes, there is a separate 12V battery for accessories, used to boot up the hybrid control system, and to provide power to the accessories when not in READY mode. When in READY mode, there is a DC-DC converter to provide 12V from the traction battery. Unlike in conventional cars, the 12V battery does not crank the gasoline engine to start it. That is done by a motor-generator powered by the traction battery.
     
    #11 CharlesH, May 30, 2017
    Last edited: May 31, 2017
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  12. Trollbait

    Trollbait It's a D&D thing

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    The same on the Chevy. I would assume that is the norm now.

    When you say turn the ignition on, you didn't actually have to restart the engine, did you?

    And cars now have a protection circuit to keep ACC mode from completely draining the starter battery. In the case of hybrids using the 12 volt for just booting up and connecting the traction pack, the 'starter'(actually a deep cycle) battery can be smaller than what is mounted in a similar ICE car.
     
    #12 Trollbait, May 31, 2017
  13. alexcue

    alexcue Active Member

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    No just the ignition, so that I could lower the windows. They won't work on ACC only.
     
    #13 alexcue, May 31, 2017
  14. Mendel Leisk

    Mendel Leisk Senior Member

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    First, I'm from the "if the car's not getting you somewhere turn it right off" school. That disclosed:

    If you want to hang out in the car with the fan going, radio on, and so on: I would follow @bisco 's advice, leave the car in ready, or you'll soon enough be shopping for new 12 volt battery.
     
    #14 Mendel Leisk, May 31, 2017
  15. jerrymildred

    jerrymildred Senior Member

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    @bisco is correct. Leave it in ready to listen to the radio and/or run the air conditioner. Unless you like dead 12V batteries. I'm glad to read that they are finally putting in timers to shut stuff off in ACC mode so people don't strand themselves.
     
    #15 jerrymildred, May 31, 2017
  16. Trollbait

    Trollbait It's a D&D thing

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    It isn't so much a timer, as much as a voltage monitor that shuts things down when the battery starts getting low. At least that is how it is in the newest cars I've had.
     
    #16 Trollbait, May 31, 2017
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  17. jerrymildred

    jerrymildred Senior Member

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    A voltage monitor would be more accurate.
     
    #17 jerrymildred, May 31, 2017
  18. stevepea

    stevepea Senior Member

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    Interesting replies everyone, thanks. You know, this is the first car I've ever had where the Accessories cuts off after a certain amount of time (had Toyotas only until the mid 1980s cars, then switched to Hondas until now). On any and all of them, the radio and/of just the plain fan (NOT the AC or heat of course) could stay on for hours if you wanted it... and never had the battery die on me. Only one time did I ever have to replace the 12V battery in one of my cars... it just got old, and after about 8-9 years, got another one. I can't imagine just the radio using all that much power so for Prius (or other similar cars) it may seem natural, but from what I've had all these years it seems really weird that it shuts off to save power. Not a big deal, just different. There are times where I have to wait around, and I'll just sit in the car for 30 mins to listen to the radio. Anyway thanks for the replies
     
    #18 stevepea, May 31, 2017
  19. Since2002

    Since2002 Senior Lurker

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    There are three modes, Accessory, On and Ready:

    Accessory mode - you can run the radio.
    On mode - you can run the fan and windows
    Ready mode - you can drive the car.

    When not pressing the brake pedal the power switch sequence is OFF -> ACC -> ON -> OFF

    Pressing the power switch while pressing the brake pedal in any mode takes it directly to READY

    In your former life the reason that you used Acc and On was because otherwise the gas engine would be constantly running, which you didn't want just so that you can listen to the radio and maybe have the fan blowing. But with the Prius you can leave it in Ready mode and ICE will only come on occasionally and briefly to keep the battery from getting too low. In fact even with A/C running ICE won't be on all the time, it will start and stop as needed to keep the battery charged.

    But if you want to use those other modes anyway, according to the owners manual (page 326) ACC shuts off after 20 minutes, ON shuts off after one-hour. Although I guess people are experiencing that ACC shuts off sooner than 20 minutes. You may want to try ON and see if it goes any longer.
     
    #19 Since2002, May 31, 2017
  20. stevepea

    stevepea Senior Member

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    I guess the Toyotas are more susceptible to draining the 12V battery, or Toyota's just being extra careful, because leaving just the radio on for 60 mins in the other cars would never drain the battery to where there was any noticeable defect, but not a big deal, just took me by surprise... thanks for the info. And at least it's not a common occurrence, when I need to leave it on for so long.. :)
     
    #20 stevepea, Jun 1, 2017
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