Please help me understand the 12 volt battery and traction battery

Discussion in 'Gen 3 Prius Technical Discussion' started by Rupert B Puppenstein, Nov 6, 2013.

  1. Rupert B Puppenstein

    Rupert B Puppenstein Active Member

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    I am far from an expert with this car, and bought it because I wanted great gas mileage. However, it appears that something may be happening with either the 12 volt or traction battery in my soon to be two year old 2011 Prius with 62,000 miles. The car starts fine, no strange noises, but the brake warning lights (ABS, Traction, and Brake) won't turn off. So, it was suggested that the battery may be the issue.

    However, the battery has never died before, it did sit off and on for a month due to my travel schedule, but last weekend, it was fine. I got a low tire pressure warning like I do every winter and filled the tires to the recommended pressure today and noticed the warning lights. I decided to drive it around a low traffic area by my house and noticed that the battery display was not fully charging even after 45 min. of driving in a hilly area that I typically have no problem getting to the full battery level with.

    I do not have the tools to check the battery level tonight, so I will be taking the car to the Toyota dealer tomorrow. But, can anyone explain to me how the 12 volt and the traction batteries work together, and how the 12 volt may affect the traction battery charging? Does Toyota usually cover issues like this, or am I looking at an expensive service bill?

    Thanks for your advice and explanations in advance.
     
  2. bisco

    bisco cookie crumbler

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    the 12v boots up the computers and the traction battery fires the ice and recharges the 12v. if the 12v is bad, the traction battery will keep charging it thus unable to recharge itself properly. but sometimes, when you are trying to see what's wrong, you think the car should be doing something it shouldn't. i wouldn't jump to any conclusions. have them read the codes and report back here. all the best!(y)
     
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  3. kbeck

    kbeck Active Member

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    Hokay. First things first: Given the warning signs you're seeing, it's unlikely that the traction battery is having trouble.

    However, a two year old car with 60K miles on it can have a bad 12V battery. Especially if, on a dark and stormy night, you left the battery on all night and it managed to do a deep nasty discharge. 12V Batteries that have had that happen to them (including any that got so badly discharged they had to be jumped) do not have long lifetimes after the fact.

    And, in fact, the 12V battery in the Prius is just a 12V lead-acid battery. It's a little strange in that it's extremely sealed; that's because it's in the passenger compartment, and safety regulators don't like the idea of acid vapor wandering around said passenger compartment where, say, people might breath it.

    Now, in the Prius, the 12V battery boots up $RANDOM computers and such left and right, but there's no starter motor, per se. The MG1/MG2 motors in the transmission, which are powered by the traction battery, do that job. So it's not like a weak battery would be detected by, say, slow cranking on a cold day. Instead, the low voltage inherent in a failing battery would be low enough to give all the electronics the fits - and, indeed, the number of bizarre trouble codes, funny lights lighting up and down, etc., have been giving both owners and dealerships the fits. Especially as battery testing appears to be a somewhat inexact science.

    In any case, putting a voltmeter across the 12V battery terminals (right hand side of the cargo compartment) is considered a Good Idea, and, if you find something less than 11V there (9 V would be a dead giveaway) it's time for a new battery. Further, practically any auto shop one would care to name probably has a battery tester: They set a bunch of knobs in various patterns, attach it to the battery, and punch a button. If the meter reads green, the battery's probably good. If not, they'll get busy trying to sell you a new one.

    By the by: If you did discharge the battery, it may take more than a couple of miles of driving around to recharge it, so a 30 minute trip to nowhere might be in order.

    There have been reports by people who (a) had discharged batteries more than expected and (b) had access to a clamp on ammeter that, in their cases, there was a amp or two "short" present when the car was off. In the couple of cases where this occurred, said people managed to troubleshoot the problem to a particular faulty component, after which they were much happier.

    Finally: Not that it happens often, but there are random reports of dead ABS/brake accumulator/other junk that gets reported around these parts. Given the large number of vehicles out there, it's a gimmie that Bad Luck happens to practically any component one would care to name, although not in large numbers. Given that your warning lights are indicting the brakes.. Basic rule: Always respect the idiot lights. If you don't, you're the idiot. Don't drive this thing 40 miles on wishful thinking; find somebody ASAP to test it (bad battery or whatever) or you'll end up wishing you had.

    KBeck
     
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  4. Rupert B Puppenstein

    Rupert B Puppenstein Active Member

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    Thank you for the explanation. I had already planned on visiting the dealership tomorrow morning, I was just hoping for any insight as to if others had experienced this and what the outcome was, and for the quick education on the batteries. I don't research well when under this amount of stress, so I appreciate the reply.
     
  5. wjtracy

    wjtracy Senior Member

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    Rupert- You really do not need tools to check 12v battery, here's the famous thread for checking Gen2 12v...not sure if there is a difference for Gen3's. Lot's of us like to replace 12v battery, when the times comes, with Optima Yellow top battery..but that takes a little DIY work. Orig 12v battery normally lasts longer than 2-yrs, but if it got discharged, that can shorten batt life.

    Weird stuff happening? MPGs dropping? Test The Battery | PriusChat
     
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  6. Rupert B Puppenstein

    Rupert B Puppenstein Active Member

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    Thanks. (y) Not sure if all those apply to the current generation, I have no idea if my other half has a voltage meter anywhere in his ridiculously messy utility closet, and I would get a nice ticket if I left the car running for nine hours trying to recharge things. :( I don't have a garage, I have a driveway and it is against the law to leave the car running unattended. I never thought they would ticket for that, but one of my neighbors was for leaving her car running to warm it up before taking her kids to school. Yes, where I live is pretty safe so the police officers don't have a whole lot to do. ;) I really should have read up on this car more before I bought it. I had no idea I would be replacing a battery at the very least once ever few years. Live and learn.
     
  7. bisco

    bisco cookie crumbler

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    that's not true, many of us have had good success with the 12v. our '04 lasted 8 years, our '08 is still fine. and that includes leaving them in an unheated garage every winter for 4-6 weeks. the secret is to never accidentally discharge them completely. if it does turn out to be your 12v, replace it with a yellowtop and you'll have better longevity. not to stress!(y)
     
  8. Rupert B Puppenstein

    Rupert B Puppenstein Active Member

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    Forgot to reply to this thread, but it looks like it was not an issue related to the battery but a brake sensor was damaged by a hair ribbon (no I don't wear ribbons in my hair) wrapping itself around the inside of the drivers front side wheel. I wish it was the 12 volt battery because it would be half the price of this happening. Prius Ownership isn't cheap for me!
     
  9. wjtracy

    wjtracy Senior Member

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    Thank you for the update....if its any consolation, believe this is the first report of hair ribbon entanglement in the history of PriusChat.
     
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  10. Rupert B Puppenstein

    Rupert B Puppenstein Active Member

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    I guess I should have taken a picture of it. Pretty sure the mechanic and service advisor did. It would make me feel better if there was some sort of prize. :)
     
  11. bisco

    bisco cookie crumbler

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    no warranty?
     
  12. Rupert B Puppenstein

    Rupert B Puppenstein Active Member

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    I am out of warranty with the mileage. :(
     
  13. Mr.Electric

    Mr.Electric Member

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    I would guess something got wrapped up in your axle and broke an abs wire. Also rats like to eat fender well wires and make abs codes.
    Also Toyota has had a recall concerning nitrogen leaking into the brake system from the accumulator that would give you a brake and abs light, and a very spongy pedal.
    If you got the code read by a mechanic you could have a much better idea what is happening.


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  14. AzWxGuy

    AzWxGuy Weather Guy

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    Does anybody know if there is a "chicken dance" to get to a signal check screen and see the battery voltage? I have a DVOM and a battery charger and do the periodic voltage check myself, but it was ever so convenient to press a couple of buttons and read the values right there in the car.
     
  15. bisco

    bisco cookie crumbler

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    yes, i can't find it, but am sure i saw it in another thread.

    check out the thread 'entering diagnostic mode'.
     
  16. GregP507

    GregP507 Senior Member

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    It's a hybrid car, so blame the battery first, and ask questions later...

    Possibly...
     

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  17. David Beale

    David Beale Senior Member

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    If the OP comes back, that can happen with -any- new "modern" car. They all have anti-lock brakes, and it sounds like that is what was damaged.

    You may want to look at warranty extension. Do keep in mind these "plans" (warranty or service) are exactly like insurance plans. Assuming for a start you buy one from a reputable company (there are some) you will pay about 20-25% more than the "average" maintenance costs for that particular vehicle. That 20-25% goes to the company to cover costs of operating the plan and profit. What these plans do is give you a budgetable yearly cost verses unpredictable and sudden large cost.
    So some owners on these plans will "get lucky" and pay much less than the service cost.
    Some owners on these plans will end up paying 20-25% more than the service cost, but only a bit at a time.
    Some owners on these plans will end up wasting their money because they never needed it. ;)
     
  18. Jonny Zero

    Jonny Zero Giggidy

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    Wow, I have seen hair ribbon damaging vacuum cleaner rotating brushes, but not ABS sensors...
     
  19. Keys

    Keys New Member

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    The posts I've seen having battery issues seem to be by those who do short drives and aren't putting a lot of miles on. My 2010 has 155k miles and my original battery is still testing strong as reported this week by my local garage.
     
  20. bisco

    bisco cookie crumbler

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