Welcome to PriusChat

We'd love to have you join our community and participate in the conversation! Sign up for FREE today.

Sign Up

12 Volt Battery Problems

Discussion in 'Gen II Prius Care, Maintenance and Troubleshooting' started by tigerpilot, Jan 28, 2011.

Social Buttons

  1. tigerpilot

    tigerpilot Member

    Joined:
    May 13, 2007
    Messages:
    123
    Likes Received:
    5
    Location:
    Naples FLorida
    Your Vehicle Year:
    2009 Prius
    2009 Prius 36,000. Driven at least 30 miles per day. Two months ago, 12 volt battery wouldn’t boot up car. Crazy messages on MFD like “Park on level surface and apply parking brake.” Jump started and drove car to the dealer. No problems found. Three weeks later, same problem. Again, no problems found but dealer replaced the battery. About three weeks later same problem except this time got the friendly Triangle illuminated. Drove to dealer and left car. I have an extended warranty so Im not too worried about any costs. The next morning the triangle was NOT lit and the only error code was low voltage. No interior lights on and current draw is normal when car is parked. Dealer at a loss and has called Toyota for help. Maybe you folks know more than the dealer. Wouldn’t be at all surprised. Welcome any suggestions.
    Regards, Don…Naples Florida
  2. richard schumacher

    richard schumacher shortbus driver

    Joined:
    Mar 27, 2004
    Messages:
    7,652
    Likes Received:
    876
    Location:
    United States
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    Prime suspects:
    - Somebody isn't closing all the doors and hatch, or shutting off all the cabin lights, or shutting off the car completely
    - Somebody likes to use the radio or other accessory with the car in ACC or IG-ON instead of turned fully ON and Ready
    - Some aftermarket electronics is junk and/or wasn't installed correctly
    - The car is not driven long enough often enough to fully charge the 12V battery
  3. tigerpilot

    tigerpilot Member

    Joined:
    May 13, 2007
    Messages:
    123
    Likes Received:
    5
    Location:
    Naples FLorida
    Your Vehicle Year:
    2009 Prius
    Don't think so.....All interior lights door, dome etc. light on OFF....Normal current drain when car is parked. Car brought to dealer exactly the same as when the problem exists.
  4. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    Messages:
    13,350
    Likes Received:
    3,189
    Location:
    Green Valley, AZ
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A
    As your title indicates, the 12V battery is the most likely suspect. It sounds like the car is getting plenty of use so the battery may just be defective. Can you get it replaced under warranty?
  5. tigerpilot

    tigerpilot Member

    Joined:
    May 13, 2007
    Messages:
    123
    Likes Received:
    5
    Location:
    Naples FLorida
    Your Vehicle Year:
    2009 Prius


    Sure I can but they say the battery in fact both the original and the replacement12 volt batteries test fine. I'm thinking that the inverter or maybe whatever controls the inverter isn't doing the job consistently. When the most recent problem occurred I monitored the voltage while driving to the dealer. It was a constant 12.5 until I turned on the headlights. It went up to 13.1 and then back when the lights were turned off. That tells me that the inverter does put out high enough voltage to charge the battery. At least sometimes.
    Please continue with any ideas.
  6. JimN

    JimN Let the games begin!

    Joined:
    Nov 26, 2006
    Messages:
    5,413
    Likes Received:
    428
    Location:
    South Jersey
    Your Vehicle Year:
    2010 Prius
    Model:
    V


    Voltage should be 14.1 not 12.5 while driving. I'd bet on the battery not taking a charge before betting on the car not trying to charge the battery.
  7. tigerpilot

    tigerpilot Member

    Joined:
    May 13, 2007
    Messages:
    123
    Likes Received:
    5
    Location:
    Naples FLorida
    Your Vehicle Year:
    2009 Prius


    The car is at the dealers and I'm picking it up tomorrow. The Toyota guru will be here later next week. I will monitor the voltage very carefully and of course have an extra battery ready.
    Thanks, Don
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    Messages:
    13,350
    Likes Received:
    3,189
    Location:
    Green Valley, AZ
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A


    Very interesting. What is your means to monitor the voltage?

    I would expect that when the Prius is READY, that 12V bus voltage would be ~13.8V - 14.0V. I've noticed on my 2007 that after some time elapses, the voltage may drop to 13.4V if electrical accessories are not in use. Your voltage readings are substantially lower and that would help to explain why your battery is becoming discharged despite all of the miles that you drive.

    You mentioned that the car logged a low-voltage DTC. With that in mind as well as the symptoms that you described in your OP, my guess is that the inverter needs to be replaced because the DC/DC converter is not doing its job.

    I suggest that if you have a decent digital multimeter available to you (Fluke is a reputable manufacturer, for example) that you use that to confirm the voltage reading of your in-car device.

    I also suggest that you use the current measurement function of the DMM to see what the quiescent current draw is, when the car is IG-OFF and all doors and hatch are closed. It should be ~20 mA which fluctuates as the security LED goes on and off.

    You can measure this either at the 12V battery negative terminal or at the dedicated positive jumpstart terminal. If the former it is easiest to disconnect the battery cable where it connects to the body. If the latter you would have to remove the 10 mm nut located at the jumpstart terminal, then lift up the wire which provides +12V to the main relay/fusebox and put the ammeter in series with that wire and the jumpstart terminal.
    1 person likes this.
  9. seredick

    seredick New Member

    Joined:
    Oct 9, 2011
    Messages:
    1
    Likes Received:
    0
    Location:
    Broadview Heights, Ohio
    Your Vehicle Year:
    2010 Prius
    Model:
    II
    I have a 2010 Prius II with just under 22,000 miles. It wouldn't start this morning. The dash indication flickered something about putting it in park. Is this a dead main battery just like the one I have in my Camry? I can't get the car into neutral to push it out of the garage. I don't know how I can have it towed? Any others with this problem. It is under warranty to 36,000 miles. I wonder if the battery is under warranty?

    Helpful comments are appreciated.

    Michael in Ohio
  10. Patrick Wong

    Patrick Wong DIY Enthusiast

    Joined:
    Mar 8, 2008
    Messages:
    13,350
    Likes Received:
    3,189
    Location:
    Green Valley, AZ
    Your Vehicle Year:
    2007 Prius
    Model:
    N/A


    This sounds like the 12V auxiliary battery is dead. (The traction battery is sometimes referred to as the "main" battery, and that probably is not the issue here.)

    To get the gear selector into N, it will be necessary to apply 12V so that the ECUs can be powered up and the parking control ECU can release the parking pawl.

    If it is not feasible to do this, the tow truck driver will probably just drag the car out of its parking area, regardless of whether the gear selector is in P.

    The 12V battery may still be under warranty, you might consult your maintenance and warranty guide so that you don't have to guess. Good luck.
    1 person likes this.
  11. zenMachine

    zenMachine Just another Onionhead

    Joined:
    Mar 3, 2007
    Messages:
    3,354
    Likes Received:
    291
    Location:
    Texas
    Your Vehicle Year:
    2007 Prius
    An extra long jumper cable might be your best bet. Good luck.
  12. 04ca-prius

    04ca-prius New Member

    Joined:
    Oct 12, 2011
    Messages:
    1
    Likes Received:
    0
    Location:
    Ca
    Your Vehicle Year:
    2004 Prius
    Model:
    N/A
    I have a 2004 with 103,875 miles on it and the start battery finally has died.
    The dealership told me 6 months ago that it looked weak but I told them that I
    would take care of it myself.

    I logged onto the internet in search of a replacement battery and found the best deal at elearnaid.com
    I ordered the battery on Monday and I received it the next day.
    The Optima battery ships with all the parts necessary to convert
    the battery posts and hook up the venting system.

    The install took about an hour and I saved major bucks over a
    dealer installed battery. The Toyota dealer wanted $213.45 plus tax
    for the cost of the battery, plus labor, which is billed at $95 an hour.
    The total estimate was $350 and I’m sure that they would not be installing a battery that is as good as the Optima battery that I purchased.

    The cost for the battery was $170 plus tax with free shipping.
    These folks have what you need to replace your start battery
    and save yourself some major bucks.
  13. Hidyho

    Hidyho Senior Member

    Joined:
    Jan 26, 2010
    Messages:
    2,517
    Likes Received:
    402
    Location:
    Texas
    Your Vehicle Year:
    2014 Prius
    Model:
    Four
    Optima now has a no extra parts drop in battery, fits nicely, no problems installing. I just installed one, and it was very simple.
  14. zenMachine

    zenMachine Just another Onionhead

    Joined:
    Mar 3, 2007
    Messages:
    3,354
    Likes Received:
    291
    Location:
    Texas
    Your Vehicle Year:
    2007 Prius


    Where did you buy yours? I might need to get one in the near future.
  15. Jim Porta

    Jim Porta Junior Member

    Joined:
    Feb 17, 2009
    Messages:
    57
    Likes Received:
    8
    Location:
    Louisville, KY
    Your Vehicle Year:
    2006 Prius
    Slightly off subject. I recently replaced my 12v battery with one from the dealer ($166). I may have pulled the trigger early. The one I pulled out still reads 12.4V after two weeks on my work bench. Does anyone know where it can be recycled or better still used till it finally dies?
    I didn't have any problems just wanted to replace it before it's 6th winter.
  16. jdcollins5

    jdcollins5 Senior Member

    Joined:
    Aug 30, 2009
    Messages:
    4,476
    Likes Received:
    935
    Location:
    Wilmington, NC
    Your Vehicle Year:
    2010 Prius
    Model:
    III


    If you take it back to the dealer where you bought the new battery they should give you a refund for the old battery core. You should see a Core Fee on the invoice for the new battery.

    I just bought a new battery for my wife's Honda and it had a $16 Core fee that was deducted since I had the old battery with me.
  17. seilerts

    seilerts Battery Curmudgeon

    Joined:
    Mar 7, 2010
    Messages:
    3,326
    Likes Received:
    1,438
    Location:
    Santa Fe, NM
    Your Vehicle Year:
    2005 Prius
    Model:
    N/A
    Junk yards will pay by the pound for your battery. I've gotten $8 for one. My Toyota dealer did not charge a core fee the last time I bought one for a friend.
  18. georockc

    georockc Junior Member

    Joined:
    Mar 16, 2009
    Messages:
    13
    Likes Received:
    0
    Location:
    Central Arizona
    Your Vehicle Year:
    2008 Prius
    I find myself in a similar situation. My 08 Prius won't start, most likely from a drained Aux battery (my fault for leaving the car with the SKS enabled). I'm in Australia and my car is being stored at my parents house in Washington state. I'm trying to get my parents some help to get the car started. The car is parked where they're unable to jump it. Would hooking up a trickle charger for awhile recharge the battery enough to get the car started?
    Thanks.
  19. DetPrius

    DetPrius Active Member

    Joined:
    Apr 24, 2009
    Messages:
    543
    Likes Received:
    89
    Location:
    Southeast Michigan
    Your Vehicle Year:
    2010 Prius
    Model:
    III
    Georockc, it can be jumped from the battery in the trunk or the jump point under the hood. With portable jumper packs now, jump starts can be done in almost any situation. A trickle charger may very well bring it up to a point it can be started, but personally, I would disconnect the battery first so as to not apply trickle charger voltage to the car's components.
  20. Gurple42

    Gurple42 New Member

    Joined:
    Mar 10, 2011
    Messages:
    355
    Likes Received:
    41
    Location:
    Santa Monica, Ca.
    Your Vehicle Year:
    2011 Prius
    Model:
    Two
    Yes it will work, I had to do it for a friend with an 07. For safety's sake I disconnected the battery cables before charging, and it worked fine. When I got the car started I took it for a nice long drive and 2 years later it's still going strong.:rockon:
Similar Threads: Volt Battery
Forum Title Date
Gen II Prius Care, Maintenance and Troubleshooting 12 volt battery replacement Oct 14, 2014
Gen III 2010+ Prius Accessories and Modifications Voltage converter for Traction Battery Generator Oct 5, 2014
Gen II Prius Care, Maintenance and Troubleshooting How do I charge the 12 volt battery? Oct 4, 2014
Generation 1 Prius Discussion 12 volt Aux battery dying; solved. Sep 9, 2014
Gen II Prius Care, Maintenance and Troubleshooting New Yellow Top Accessory battery, but still have voltage issues Sep 1, 2014