12V battery is being drained

Discussion in 'Gen 3 Prius Technical Discussion' started by Codyawano, Dec 23, 2018.

  1. Codyawano

    Codyawano New Member

    Joined:
    Dec 23, 2018
    2
    0
    0
    Location:
    Ogden
    Vehicle:
    2010 Prius
    Model:
    Three
    I have a 2010 Prius and just recently when I turned off the car and got out of the car it beeped 3 times like it was left on but it was off. When I came back to my car the 12V was dead. Also the sound system used to turn on and off with the car but now I have to do it manually.
     
  2. Codyawano

    Codyawano New Member

    Joined:
    Dec 23, 2018
    2
    0
    0
    Location:
    Ogden
    Vehicle:
    2010 Prius
    Model:
    Three
    I also just replaced the battery in the key fob and the key isn't working, can't lock or unlock my car.
     
  3. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    76,999
    32,365
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    welcome!

    what have you done about the dead 12v? nothing will work correctly while it is low.

    it sounds to me like a door isn't closing properly, that's when you get 3 beeps. it is usually the hatch.
     
    scona likes this.
  4. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

    Joined:
    Oct 17, 2010
    32,047
    21,029
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Yeah check the 12 volt battery. At least with a digital volt meter, with the car off. and post the reading.

    Is it the original battery? Then it's replacement time, regardless.
     
    scona likes this.
  5. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    1,373
    659
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    This. If it is 8 years old, what is "draining" the battery is: The battery itself.
     
    scona likes this.
  6. Grit

    Grit Senior Member

    Joined:
    Aug 22, 2017
    1,596
    1,413
    1
    Location:
    BOY
    Vehicle:
    2012 Prius
    Model:
    Four
    With info given, 12v not being drain. Instead 12v is near end of life- not holding stable charge.

    Replace batt now or have road side assistant on speed dial.
     
    Raytheeagle likes this.
  7. Jana26

    Jana26 New Member

    Joined:
    Jan 2, 2019
    9
    2
    0
    Location:
    MO
    Vehicle:
    2013 Prius
    Model:
    Three
    I've got basically the same problem but no beeping. I came back from an 11 day trip to a totally dead 12 volt battery. Had it jumped, took it to the dealer for a new battery. Four days later, totally dead again. Had it jumped, took it in and left it for a few days. They charged up the new battery, checked "stuff" out, started it and drove it a few times, but couldn't find anything wrong. Two days later, totally dead again. They've now had it for over a week and can't find anything wrong. If it had an alternator, I'd think it was that, but...

    I always turn the headlights off manually, hardly ever really listen to the radio, and have checked all ideas of what else I could be doing to cause it and I'm innocent!

    Any ideas?
     
    bisco likes this.
  8. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    76,999
    32,365
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    welcome!

    my only idea is that someone needs to go through it thoroughly to find the culprit.

    if you can't diy, find another shoppe, they sound clueless

    1) test battery with volt meter after car has been off for 12 hours

    2) make sure all connections are clean and tight

    3) measure parasitic drain with car off and compare to specification

    4) measure battery with car ready and compare to spec, to make sure it is charging properly

    5) make sure all lights go out when doors are closed, especially hatch and hatch light.

    6) all the best!(y)
     
    scona and Jana26 like this.
  9. Jana26

    Jana26 New Member

    Joined:
    Jan 2, 2019
    9
    2
    0
    Location:
    MO
    Vehicle:
    2013 Prius
    Model:
    Three
    Thanks. I have nagged them about checking each time they drive it to see if the battery is being charged. Sadly they should have thought of that themselves. AAA had checked the connections, etc and said there was no problem there.

    Now, the other issue will be that the draining of the new battery (twice so far) has shortened it's lifespan. I was going to insist on another new battery once they solve the problem but, if I take it somewhere else, the dealer might not be so willing to do that. Another fight. We'll see.

    Thanks for the input and wish me luck.
     
  10. FuelMiser

    FuelMiser Active Member

    Joined:
    Jun 29, 2008
    693
    458
    0
    Location:
    Monument, CO
    Vehicle:
    2016 Prius
    Model:
    Touring
    Do you have anything plugged in to your OBD-II or USB?
     
    Mendel Leisk and bisco like this.
  11. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

    Joined:
    Oct 17, 2010
    32,047
    21,029
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    You could have some constant drain, more than the typical low level drain all modern cars have. Test the at-rest amperage:

    1. Disconnect the battery's negative cable.
    2. With a couple of leads (say at least a yard long, preferably with alligator clips at both ends), connect one to the battery negative post, the other to car ground.
    3. run the leads out through the hatch threshold, then gently close the hatch. The car's 12 volt is now hooked up, albeit just through those thin leads.
    4. Wait about 1/2 hour, ensure the fobs are well away from the car.
    5. Hook up a multimeter to the leads, set to amp scale first, and if no reaction (there shouldn't be) switch to milliamps.

    I observed 16~20 milliamps doing this, with periodic spikes (every 5~10 seconds) to around 40 milliamps.

    If you've got significantly higher readings, you need to troubleshoot, say disconnect one fuse at a time, see what happens.
     
  12. Maarten28

    Maarten28 Active Member

    Joined:
    Jul 13, 2014
    288
    136
    1
    Location:
    Netherlands
    Vehicle:
    2011 Prius
    Model:
    Three
    When you turn it off, pull out a few fuses and see if the problem persists. Then try to narrow it down by adding or removing fuses.
    Or see if you can measure the current going through a fuse.
     
  13. Mendel Leisk

    Mendel Leisk Sidewalk Supervisor

    Joined:
    Oct 17, 2010
    32,047
    21,029
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Google:

    Eric the Car Guy Battery Drain
     
  14. Jana26

    Jana26 New Member

    Joined:
    Jan 2, 2019
    9
    2
    0
    Location:
    MO
    Vehicle:
    2013 Prius
    Model:
    Three
    Update: Apparently it's not draining the battery. It just looks like that because there are no lights, no nothing. The dealer has had it more than I have this past 50 days. They even brought in a tech from Toyota Corp trying to figure out what's going on. Once they get it and jump it to get it into the shop, it starts every time. They think it's a fuse but can't check it until the car acts up. And it won't act up for them.

    Side note: they tried to jump it once at the battery but it wouldn't start.

    They are baffled. Any ideas????
     
  15. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    1,373
    659
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    This suggestion was given a couple of months ago but it bears repeating again NOW.
    Sometimes even good "mechanics" just don't seem to understand batteries.

    Similar problems have sometimes been solved by "fixing" a bad chassis connection on the negative battery cable too.
     
    Grit likes this.
  16. Jana26

    Jana26 New Member

    Joined:
    Jan 2, 2019
    9
    2
    0
    Location:
    MO
    Vehicle:
    2013 Prius
    Model:
    Three
    Thanks. The battery has been replaced but the problem still exists.

    I'll pass your suggestion along.
     
  17. sam spade 2

    sam spade 2 Senior Member

    Joined:
    Mar 31, 2018
    1,373
    659
    0
    Location:
    USA
    Vehicle:
    2017 Prius c
    Model:
    Four
    They may need to send a tech to YOU when it fails.
    No that is not "normal" procedure but it might be the only way to solve anything.

    There are things that can be checked.......but nobody trains their "mechanics" these day in how the systems in the vehicle actually WORK.
    As a result, they have no clue how to actually troubleshoot a problem.
     
Loading...