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Radio switching off

Discussion in 'Gen 2 Prius Main Forum' started by Lodrun, Feb 9, 2012.

  1. Lodrun

    Lodrun My proper car is an MGC

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    While I wait for my daughter to have her music lesson I sit in the Prius listening to the radio with the Power button selected to accessories only. The weather is cold at the moment (typically just above 0C) After a few minutes the sound goes off and cannot be restored without powering up the motors. If I return to accessories power, the same thing happens again.

    When the motors are subsequently powered up, the big red central warning triangle comes on for a couple of seconds. No further problems, with the car driving perfectly and the radio fully working.

    Is this a temperature/battery problem and is there anything I can do about it?
     
    #1 Lodrun, Feb 9, 2012
  2. cwerdna

    cwerdna Senior Member

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    Don't do that. You should sit in READY mode as the 12 volt is tiny and can be drained very quickly. Nothing will charge the 12 volt while sitting in ACC mode.

    I also recommend testing your 12 volt after the car has sat overnight via the method at http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html. Tell us the readings after each step. You don't have to turn the headlights all the way. Just going back and forth between parking lights and off is enough.

    Your 12 volt might be due for replacement anyway and you running it flat isn't doing it any good.
     
    #2 cwerdna, Feb 9, 2012
  3. DetPrius

    DetPrius Active Member

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    I believe the radio draws very little power, doesn't it? I have had the radio on for a couple hours at a time and had no problem. I don't know what it draws but I know there are smart people here who can do the simple math to determine how many hours the battery can power the radio based on the draw of the radio and the amp hour rating of the battery. If 30 minutes of the radio kills the battery, that must be one bad battery. I'd like to see the numbers if anyone knows the draw of the radio and AH rating of the battery.
     
    #3 DetPrius, Feb 9, 2012
  4. qbee42

    qbee42 My other car is a boat

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    This would be a useful calculation, assuming that you remove the radio and battery from the car and run them in isolation. I assume most people aren't going to do that.

    When you run your Prius in Acc mode, *all* of the accessories are powered, not just the radio. The power draw is not insignificant. This is why the Prius has an auto-off timer that automatically shuts off the radio after some predetermined interval. I believe the interval is one hour for a Gen II, but I would have to look it up to be certain.

    As stated above, don't use Acc mode for extended listening.

    Tom
     
    #4 qbee42, Feb 9, 2012
  5. DetPrius

    DetPrius Active Member

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    Yes Tom, the auto off is 1 hour on the Gen III as well. I think I can figure out how to get the draw in ACC mode with an electrical meter so maybe I'll do it when I get a little free time. I did it once on our Odyssey when I had a battery go dead when nothing was on and it sat for a week and I wanted to know what the draw was as the vehicle sat with nothing on.
     
    #5 DetPrius, Feb 9, 2012
  6. Lodrun

    Lodrun My proper car is an MGC

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    Thanks for all this. It confirms what I thought. My Prius is 4 years old so I doubt that the 12V battery needs replacing - it is probably the very cold weather reducing its capacity.

    I don't really want to sit for half an hour in READY mode with the engine running if I can avoid it. Can the 12V battery be charged periodically from a trickle charger? Does it need to be disconnected first?
     
    #6 Lodrun, Feb 16, 2012
  7. uart

    uart Senior Member

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    I wouldn't make that assumption. Test the battery.
     
    #7 uart, Feb 16, 2012
  8. uart

    uart Senior Member

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    Yes, if someone can measure the standby current in accessory mode with everything off (multifunction display off, fans off, radio off) that would be really interesting to know.
     
    #8 uart, Feb 16, 2012
  9. qbee42

    qbee42 My other car is a boat

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    To do it right, you need to log the quiescent draw over time. The Prius has a number of systems that switch on and off automatically. Some draw a fair amount of current when running, but run intermittently, so it would be easy to miss their contribution when doing a short test.

    Tom
     
    #9 qbee42, Feb 16, 2012
  10. Lodrun

    Lodrun My proper car is an MGC

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    Does anyone know if the 12V battery can be trickle-charged from the jump start point without disconnecting the battery?
     
    #10 Lodrun, Feb 17, 2012
  11. Lodrun

    Lodrun My proper car is an MGC

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    Does anyone know if it OK to trickle-charge the 12V battery from the jump start point without disconnecting it first?
     
    #11 Lodrun, Feb 17, 2012
  12. uart

    uart Senior Member

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    Yes it's ok to charge the battery from the jump start terminal, that's how it's often done.
     
    #12 uart, Feb 17, 2012
  13. Lodrun

    Lodrun My proper car is an MGC

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    Yesterday I checked the battery readings as suggested by cawerdna: only 9.7V off-line, charging at 14.1V when car powered up. I connected a trickle charger to the jumpstart point in the fuse box and charged it for about 5 hours. Charging current was 3.5 Amps initially, falling to 2 Amps after a few minutes. (Although the handbook recommends disconnecting the battery for charging, I couldn't see the need for it since the system is designed for a jump start battery to be connected at this point anyway.) After charging, battery voltage was 12.1, which is maintained today.

    Hoping problem solved. If not will have to replace the battery.

    Thanks to all for your help.
     
    #13 Lodrun, Feb 18, 2012
  14. Lodrun

    Lodrun My proper car is an MGC

    Joined:
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    Yesterday I checked the battery readings as suggested by cawerdna: only 9.7V off-line, charging at 14.1V when car powered up. I connected a trickle charger to the jumpstart point in the fuse box and charged it for about 5 hours. Charging current was 3.5 Amps initially, falling to 2 Amps after a few minutes. (Although the handbook recommends disconnecting the battery for charging, I couldn't see the need for it since the system is designed for a jump start battery to be connected at this point anyway.) After charging, battery voltage was 12.1, which is maintained today.

    Hoping problem solved. If not will have to replace the battery.

    Thanks to all for your help.
     
    #14 Lodrun, Feb 18, 2012
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