1. Attachments are working again! Check out this thread for more details and to report any other bugs.

At what point do you replace the 12v battery?

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by mikefocke, Jul 1, 2016.

  1. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

    Joined:
    Nov 3, 2012
    3,626
    1,623
    0
    Location:
    Sanford, NC
    Vehicle:
    Other Hybrid
    Model:
    Limited
    '12 v. 32k miles. Everything original but the windshield wipers. But I got to thinking the other day that the 12v has 4 years of use.

    I'm not adverse to spending $ to replace it early if it prevents a future problem. Just did that on my wife's '11 Avalon. Neither do I want to spend foolishly. And we know the 12v in a Prius is used very differently than in a normal ICE vehicle. But what are folks experiences with those differences?

    At my 30k check up, the battery condition written in the service report by the service tech was "OK". No voltage or load test reading.

    Suggestions?
     
  2. rdgrimes

    rdgrimes Senior Member

    Joined:
    Jun 7, 2013
    1,740
    444
    4
    Location:
    New Mexico, USA
    Vehicle:
    2018 Prius Prime
    Model:
    N/A
    The first indication of trouble will be a failure to start the system. I'm not a person who waits for that to happen, YMMV.
     
  3. Kenny94945

    Kenny94945 Active Member

    Joined:
    Mar 24, 2016
    757
    387
    0
    Location:
    Sausalito
    Vehicle:
    2016 Prius v wagon
    Model:
    Four
    See post # 2.
    First time starting difficulty is the clue.
    Also if listening to the stereo for 20 minutes causes a no start is a clue.

    Below is not Prius specific but based on my experiences:
    Conservatively batteries last 3 years...so change every 3 three years and one is usually "golden" and never stranded.
    Typical life is 4 to 5 years.
    6 years...you are on borrowed time IMO.
     
    Montgomery and Mendel Leisk like this.
  4. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,463
    38,101
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Get a half-decent digital multimeter, and periodically check voltage. If you see numbers 12.6 or higher you've got a very healthy battery. 12.4~12.6 is "middle aged". Lower than 12.4, it's time to start shopping.

    To really check health, look into some sort of digital load tester, like (prosumer level) Solar BA5.

    To recover from partial drains, an intelligent charger in the 4 amp range is good.

    All of the above will set you back close to the cost of a new battery, but keep you from being in the dark, and will last foreverer. Good for helping family and friends too.
     
    Clark_Kent, Kermit262 and bisco like this.
  5. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,861
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    2012 w/ 42k. car is garaged and doesn't see much heat or abuse. 12v is still in good shape, but i'm more in the camp of; if it ain't broke, don't fix it.:cool:

    i have found on my past two prius that if you don't run the battery down, it's good for 7 or 8 years.
    of course, that includes time spent at the dealership before purchase, where you may not know if it was run down.
    i do check the standing voltage every 6 months or so, as mendel mentions above. takes 2 minutes under the hood.
     
    #5 bisco, Jul 2, 2016
    Last edited: Jul 2, 2016
  6. DonDNH

    DonDNH Senior Member

    Joined:
    Feb 3, 2004
    1,711
    654
    0
    Location:
    Nashua, NH
    Vehicle:
    2016 Prius
    Model:
    Four Touring
    My 2010 12v battery lasted 64 months. Of course it failed on a -5F morning in January. Luckily I didn't really have to get anywhere important. AAA got me started and and Toyota replaced the battery.
     
  7. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,463
    38,101
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    A jump pack is another good item to have. Once you get all this crap you rarely need it, but get to play hero, lol.
     
  8. mikefocke

    mikefocke Prius v Three 2012, Avalon 2011

    Joined:
    Nov 3, 2012
    3,626
    1,623
    0
    Location:
    Sanford, NC
    Vehicle:
    Other Hybrid
    Model:
    Limited
    Since the battery really doesn't start the engine but just the electronics to start the engine, unlike the typical ICE car, I wasn't sure what the load test readings would need to be. I have all the meters and a load tester sitting 10 feet from the car. I carry a great thick cable set of long jumpers. And I'm the only one to drive the car generally and can RTFM if I need to.

    What settings get lost when you swap the battery? Radio settings, dealer set options like reverse and seat belt warnings?

    Probably just replace in the fall based on 4 years. Or is the devil you know gonna be better than the devil you buy ....
     
    bisco likes this.
  9. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,463
    38,101
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    deleted (double post)
     
    #9 Mendel Leisk, Jul 2, 2016
    Last edited: Jul 6, 2016
  10. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,463
    38,101
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Trip meters (if you're tracking mpg it's good to rely on the odometer, it's dependable), and maybe auto-up on the windows will need to relearn. You can get an OBD cable "memory saver" that plugs into jump pack.
     
    bisco likes this.
  11. catgic

    catgic Mastr & Commandr Hybrid Guru

    Joined:
    Jul 7, 2007
    586
    140
    1
    Location:
    HTTP 404 Not Found
    Vehicle:
    2012 Prius v wagon
    Model:
    Five
    Gathered Prius Vee'erz - FWIW FYI: 2012 Prius v Five put into service December 2011, 47,000 miles on the odometer, operated in Central Florida climate, drive it "Hybrid $mart," Accessory Battery remains robustly healthy.
     
    Kermit262 and bisco like this.
  12. Silver Pine Mica

    Silver Pine Mica Junior Member

    Joined:
    Feb 9, 2013
    48
    22
    0
    Location:
    Columbia, Missouri
    Vehicle:
    2006 Prius
    Model:
    N/A
    My experience has been these batteries are fine for six years+ as long as you don't leave anything on, like a vanity light. I recommend a 1.5 Amp battery minder 1510 to charge it along with an OBDII adapter so you don't have to access the battery or pop the hood to charge. This also makes it easy to check the voltage with a voltmeter, and as long as it is above 11.8v you are not in immediate risk of being stranded. If you charge it regularly it should be good for a very long time. The battery minder has a pulse desulphation feature and operates below 15v so it should be safe for the prius while extending battery life (it brought voltage up on my four year old battery from 12 to 13.2 volts gradually). Be aware that the OBDII port should not be subject to more than 3amps of current. The Battery Tender brand of OBDII adapter works with the Battery minder connector. There is an inline fuse that can get loose and then blow out but fuses are cheap (happened to me once, noticed it was loose and blown after I noticed it didn't work anymore). Anyways the batteryminder costs about a third of the cost of a new battery and an auto ranging voltmeter is $20 on amazon, manual range voltmeters can be less than $10. Even if you eventually replace the battery, you should make sure the new one is fully charged before you install it.

    The battery just boots the computer so cold cranking amps isn't important, voltage is. Keeping voltage above 12.4v prevents most sulfation. Also the OBDII voltage is live while the car is off, the 12v charge port turns off.
     
    bisco likes this.
  13. mmmodem

    mmmodem Senior Taste Tester

    Joined:
    Nov 17, 2011
    2,732
    1,703
    0
    Location:
    Bay Area, CA
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    I have a 2012 with 109k miles on the original battery. I don't want to spend foolishly either. Although, I admit, a dead battery is no issue for me to replace and I am extremely lazy. How is the 12v used differently in a Prius?

    Anyway, my biggest issue is regaining the backup beep. I don't go to the dealer anymore so I'm going to have to buy an OBDII reader as well. I bought a portable jump pack so I can continue using the original 12v battery as long as I can. I'll probably cap it at 6 years as I don't know of anyone making it to 7.
     
  14. Silver Pine Mica

    Silver Pine Mica Junior Member

    Joined:
    Feb 9, 2013
    48
    22
    0
    Location:
    Columbia, Missouri
    Vehicle:
    2006 Prius
    Model:
    N/A
    In the prius the 12v boots the ecu. The ecu then tells the hybrid system to spin the engine and power up the inverter so you have 13.8+ volts from the inverter as soon as the ecu boots. Only once the hybrid system has the engine up to 1000 rpm does it add gas and spark and by that time the 12v battery is just chillin. This is why bad batteries give no hard start warning signs in a prius. When the voltage on the 12v gets less than 11v you can get weird glitches from the computer not getting enough at bootup or suddenly fail to boot.
    I never disabled the beep but The obd reader i got that works with torque over bluetooth is ScanTool 427201 OBDLink LX Bluetooth: Professional OBD-II Scan Tool for Android & Windows
     
    mmmodem likes this.
  15. les.warden

    les.warden Junior Member

    Joined:
    Jul 9, 2015
    22
    8
    0
    Location:
    Central illinois
    Vehicle:
    2008 Prius
    Model:
    II
    First indicator on our 2008 was the "red triangle exclamation" light came on. Actually drove it for almost a week while trying to figure out why this light was on. Toyota dealer said it would go off after a couple days. Whaaaaat????? Obviously they failed on this one!! Luckily, it wouldn't start while parked in the cozy garage. Lucked out here! I replaced it with a Optima Yellow Top 12V battery. Maybe overkill but should outlast the car.


    Tapping on my iPhone
     
    #15 les.warden, Jul 3, 2016
    Last edited: Jul 3, 2016
    bisco likes this.
  16. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,861
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    just tested mine after sitting overnight, 12.87 volts.
     
    Silver Pine Mica likes this.
  17. cipsaz187

    cipsaz187 Member

    Joined:
    Feb 19, 2014
    147
    42
    0
    Vehicle:
    2012 Prius
    Model:
    Four
    That's a pretty good voltage. I am getting the 12.22V after overnight on my 2012. I also don't do long trips to fully charge the battery. I keep it on maintainer occasionally to fully charge the battery, but after days it goes back to its regular 12.2 resting voltage. I am not sure if I would get a higher resting voltage by driving more.

    I don't really want to buy a new battery yet. I still think it can last some time. Just weeks ago was -12F and it started just fine. Thinking about getting a battery pack.
     
    #17 cipsaz187, Jan 2, 2017
    Last edited: Jan 2, 2017
    bisco likes this.
  18. bisco

    bisco cookie crumbler

    Joined:
    May 11, 2005
    107,571
    48,861
    0
    Location:
    boston
    Vehicle:
    2012 Prius Plug-in
    Model:
    Plug-in Base
    you probably have a few more years, if you don't drain it. one of the benefits of pip is a top up every time you charge.
     
  19. Mendel Leisk

    Mendel Leisk Senior Member

    Joined:
    Oct 17, 2010
    54,463
    38,101
    80
    Location:
    Greater Vancouver, British Columbia, Canada
    Vehicle:
    2010 Prius
    Model:
    Touring
    Our car sometimes sits 3 days, maybe 4. If it's late in the day, after a day without driving, I've taken now to just hooking up the 12 volt charger. I let it run to completion of it's cycle, then leave it connected until we do need the car.
     
  20. cipsaz187

    cipsaz187 Member

    Joined:
    Feb 19, 2014
    147
    42
    0
    Vehicle:
    2012 Prius
    Model:
    Four
    So a fully charged battery read 13.30V. Immediately started driving in 35F weather and within minutes I was on EV. A 12 min drive gave me 51mpg.

    With a weak battery in the same weather I get 43mpg driving the same distance. The EV would probably kick in after 10min or so.

    So yea, the weak battery does effect the mpg and its really obvious.
     
    bisco likes this.