Battery Parasitic Drain`

Discussion in 'Gen 3 Prius Main Forum' started by William Yorston, Jan 22, 2025.

  1. William Yorston

    William Yorston Junior Member

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    OK, quick summary, installed adroid head unit in my Gen3. Besides the main power from the ignition it has a standby power input. Since hooking that up it is draining the battery in a couple of days. I installed a remote battery disconnect and it works well. The only problem is when I use that it loses the car settings completely, such as driving mode, clock, and computer etc. That's ok if long storage is required but inconvenient for daily use. For example it doesn't default to ECO mode. I can't remember what wire I spliced in for this standby power, and now wish to cut that off and just power the head unit via the ign switch. Any help for the color code for the standby power wire so I can try eliminating that power input. I no longer have the diagram for the head unit so a bit stuck. Thanks in advance.
     
  2. ChapmanF

    ChapmanF Senior Member

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    Does this help?

    https://priuschat.com/posts/3177861
     
  3. Paul Gregory

    Paul Gregory Active Member

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    I learned to live with parasitic drain with my Gen 3, but it was measured at 50 mA, and was fairly constant, so as long as I drove it once a week, the battery was never dead.

    My 2024 Prius Prime is a whole different story. I once measured the drain at 330 mA, but it was much worse than that at times. My workaround isn't ideal, but I installed a NOCO battery maintainer under the hood, and I plug it in whenever I can. I also installed an auxiliary 100 mA lithium battery that only comes into play if I need it. I haven't needed it so far.
     
  4. William Yorston

    William Yorston Junior Member

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    Thanks ChapmanF, I will look closer at the L40, I guess I did such a good jobe with shrink etc I can't tell what nI did and what the factory did. Lol
     
  5. William Yorston

    William Yorston Junior Member

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    I never had an issue before I installed the Android head unit. I was diagnosed with cancer last June, the car sat a lot and drained the battery while I was hospitalized. Been fighting it ever since. I have a new Lithium Ion Hybrid pack, new 12v battery, had it plugged into a maintainer, all was fine until yesterday, wouldn't start, when jumped started but Hybrid error showing, etc. I can clear the error with Dr Prius but I need to cut the wire for the memory maintainer on the head unit, like I said I can disconnet the battery with a remote device but then it loses vehicle memory data including mode. Just trying to figure our, reverse engineer what I did.
     
  6. Grit

    Grit Senior Member

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    You should install the remote kill into the android head unit and remotely kill the unit when parked instead of the entire vehicle 12v battery.
     
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  7. Frontporch

    Frontporch Member

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    Very little experience with aftermarket radio installs, but I did run a foul installing one in a 96 BMW. I regretted that because I had to provide an aftermarket amplifier and separate crossovers as well.

    If it were me, I would do some research online and try to get the installation guide for the radio... maybe contact the manufacturer.

    I also think there is kind of a universal wiring to these head units that might help... found this online.
    • The 12V battery wire is yellow, the accessory wire is red, and the dimmer/illumination wire is orange with a white stripe.
    • The right-front speaker wires are gray, left-front speakers are white, right-rear speakers are purple, and left-rear speakers are green.
    • Ground wires are black, antenna wires are blue, and amplifier wires are blue with a white stripe.
     
  8. Grit

    Grit Senior Member

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    Good to know Toyota made things bad to worse so we can buy even more unnecessary things to keep things working when parked for days.
     
  9. William Yorston

    William Yorston Junior Member

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    ok, and that's a big ok. I have still not gotten to the bottom of this drain issue and now the rear hacth problem has popped uo it's ugly head.
    working my way through this I remembered the rear hatch lift has been a little wondky evern since I had a load of gravel (sand) deposit a bunch into that rear latch assemply. It became a bit picky on when the door switch was atctivated like whe you press it to open the tailgate. I noticed some additional draw when in the lockeded position. The mechanism when closed goes through 2 clicks. 1st is the door is locked, 2nd is the door open/closed, the warning one sees on the the dash. if i use a screwdriver and go through both clicks the door open indicator goes away and I can set the alarm. My hatch when closed is only getting to the first click (depth) within the actuator, I see no adjustment to raise the actuator or lower the activator/arm on the rear hatch. I first thought elongate the mounting how to raise the acuator position, does this make sense?
     
    #9 William Yorston, Feb 2, 2025
    Last edited: Feb 2, 2025
  10. William Yorston

    William Yorston Junior Member

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    It was the door seal in the way, lock and alarm, no door ajar, works correctly with new actuator. now I will go back to the parasitic drain issue. I had installed a wireless battery disconnect, that unit also has a draw so took it out.. I now have everything back to the factory as was positions. Since my health went south in June 2024, the poor prius just sat for a long time, I would say about 2 months. It sat, i sat but now I want a starting car back. So, all power stuff back to normal, I hace a new MAS comining tomorrow, and then hopefully done. Thanks for the help.
     
    #10 William Yorston, Feb 2, 2025
    Last edited: Feb 2, 2025
  11. rjparker

    rjparker Tu Humilde Sirviente

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    Factory radio back in?

    What is a MAS?

    The constant power for the radio is fed through the "15 amp Rad 1" fuse
     
    #11 rjparker, Feb 2, 2025
    Last edited: Feb 2, 2025
  12. William Yorston

    William Yorston Junior Member

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    #12 William Yorston, Feb 6, 2025
    Last edited: Feb 6, 2025
  13. rjparker

    rjparker Tu Humilde Sirviente

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    ok it's MAF
     
  14. Frontporch

    Frontporch Member

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    I have a feeling you know this, but these cars don't always power down when you get out and lock the doors. When I was searching out some parasitic drains in my 2005 Honda Odyssey, I had to wait several minutes for the car to really quiet down. I believe also removing the battery cable to measure amperage can cause the car to wake back up, so it had to be connected through a multimeter like that for a while.
     
  15. Paul Gregory

    Paul Gregory Active Member

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    I know that my battery didn't go dead in 2 hours just from a 330 mA drain. That's what I measured once, using a clamp DC ammeter. It was often more or less than that.

    It's just a fact that it happened; an unacceptably rapid battery drain, that left me inconvenienced.
    Several times. I carry a booster pack in my car as a result.