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Is it just the 12 volt battery, or could it be something more?

Discussion in 'Gen 4 Prius Main Forum' started by PriusRos, Mar 22, 2023.

  1. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    The other day when I turned my car on for the first time, I got strange messages that said something like,
    Car is in N, shift to P. Then, Low 12 volt Battery, Apply Parking Brake Securely While Parking. After a little while, when I tried to turn it on again, the screen remained completely black.

    I called AAA. The battery guy came out, charged it, and the car started right up. He said the battery's good and he doesn't know why it would have discharged. He told me a new battery would be $190 but assured me I didn't need a new one - even though I told him that my battery was the original one, about 7 years old.

    So, I then drove it to pick up some dry cleaning. There was a long line and I waited outside for about 10 minutes, listening to something on the radio before going in. The car was off for about 15 minutes while I was inside. When I restarted, the display came on, but said Not Ready to Drive. So, I called AAA again, thinking I should get it towed to be checked out to make sure it wasn't just the battery. While I was waiting, I tried again, and this time it came on and I was able to drive it so called the tow-truck driver to tell him not to come - but he said he was close and maybe I should wait till he got there to make sure. Sure enough, when he arrived and I turned it back on, it again gave me the Not Ready to Drive message. So, I told him I'd better tow it to the Toyota dealership (instead of to AAA) so I can get it checked out, and while I was looking up the phone number it came back on to Ready mode. Since it was already late in the day, I told him to cancel the tow and I'd drive it home and deal with it the next day. He probably thought I was a crazy little lady who couldn't make up her mind.

    This morning I called Toyota to ask how much it would cost to have it checked out and replace the battery. They said the diagnostic would be $123 and the battery would cost somewhere between $370 and $450! Glad I didn't get it towed there.

    Sorry for the longwinded story, but does this sound like all I need to do is replace the battery? If so, why do you think the first guy told me the battery was "strong" and didn't need replacing yet?
     
    #1 PriusRos, Mar 22, 2023
    Last edited: Mar 22, 2023
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  2. Mendel Leisk

    Mendel Leisk Senior Member

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    There are automotive retailers selling batteries, that will have electronic load testers, comparable to what the dealership use. And usually do the test for free. Check first with a few, if they have compatible battery, should be cheaper route.

    for something like $50~80, there’s DIY level testers available. Solar BA9 is the type I’m using, albeit an older version.
     
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  3. sam spade 2

    sam spade 2 Senior Member

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    Yes.
    The guy is a tow truck driver.
    Even "real" mechanics sometimes don't understand how to test a battery.
    Not a big surprise.
    A 7 year old battery is past it's prime.
    Get a new one.

    THEN......of course it could be "something more" but you can't know that until you have a known good battery.
     
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  4. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Actually, he wasn't a tow-truck driver (AAA differentiates between the battery guy and the towing guy) and he supposedly tested my battery. But you're right. I'm going to get a new battery anyway and hope that does the trick.

    My reason for posting here is to find out whether these messages are typical of the messages one gets from dying battery or indicative of something else.
     
  5. bisco

    bisco cookie crumbler

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    the message said low 12v, and the rest is probably related. prius can do a lot of funny things when the ecu's don't get the minimum voltage required.
    so the question is, why is the 12v volt not holding a charge?
    it could simply be that you don't drive enough, or it could be something more.
    i agree with replacing it and go from there. why he meter showed it as good i can't explain, but we have seen it before.
     
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  6. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    I have been driving fairly regularly and think I had just driven it the day before it decided to have a tantrum. I thought maybe, just maybe, I had inadvertently left it on in accessory mode - I've sometimes pressed the Power button to turn it off when it's already off - but I don't think so because it would have given a whine when I tried to lock it. I suppose the battery is just worn out.
     
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  7. bisco

    bisco cookie crumbler

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    mine lasted 6 years. some people get more, but you can't expect it. it depends on a wide variety of conditions.
     
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  8. Prius2016excel

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    Strongly suspect it’s the 12v. Mine was dodgy when I bought it and it caused similar problems. It pissed me off bigley at the time. Bearing in mind the Prius 12v doesn’t have to generate power to start the ICE I was mystified at the time (and still am) as to why it’s so flaky?

    In a non hybrid there’s warning signs the 12v is on the way out —struggling starter motor and slow electric windows the most obvious. All the Prius has to do is start the electronics but one moment it was working and the next it was refusing to get the car into READY and needed a jump start.
     
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  9. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Yep ... that's why I was surprised. Worked fine until it didn't. No warning - and the AAA battery service guy said it was fine - just needed a jump start.
     
  10. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Thank you everyone who responded. Here's the update:

    After reading all your responses, I decided I should start by getting a new battery and hope that solves the problem. I first called AAA Roadside Assistance to find out if they had the right battery - they told me it would depend on the individual contractor and whether they would have it on their truck. They contractor called me back immediately but told me that they don't carry that particular battery and that none of the trucks would have it. I then called the local AAA service center, who also told me they didn't have it in stock, and Batteries Plus, who said they did have it and quoted an installed price that was actually $25 less than the AAA price. So, I asked AAA to come back out and give me a jump start so I could drive to Batteries Plus. He came almost immediately, and, like the first guy, jump started the car and told me the battery was still strong. I had thought maybe the other AAA guy either didn't know what he was talking about, just didn't want to do the work, or didn't have the battery available, but here's a second guy telling me the same thing - but he also told me that they just don't change the batteries for this type of car!

    So, I drove it to Batteries Plus and they did have the correct battery - but it took the guy, with the occasional assistance of 2 other people, around an hour to get the old one out and the new one in! He seemed to have a lot of difficulty reaching the bolt holding it in place and tried all sorts of different types of wrenches in different configurations. One of the other guys was actually the store owner, who happened to come by, and who knew about these cars. He told me it was one of the more difficult cars to work on. (And to think, my significant other was telling me to go buy the battery and we could change it ourselves - yeah, right!) Anyway, I tried it today and it's working. Yay! Are the batteries on these cars always that difficult to change?

    I still don't understand why two different AAA battery technicians, who should be able to know whether the battery is healthy enough to hold a charge, told me it was fine, when it clearly wasn't. I forgot to ask the Batteries Plus store owner, who was the only one who seemed to know what he was talking about, why he thinks they thought the old battery was still healthy.
     
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  11. bisco

    bisco cookie crumbler

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    the difficulty is simply because the battery is tucked into the corner under the hatch.

    once you have done it once, it's fairly simple. but not that many people do it more than once, if ever.

    nothing is as easy as raising the hood, unscrewing the two clamps and swapping batteries, which is the way cars were forever.
    but new technologies have made things more exciting!

    the reason aaa doesn't know how to test the battery properly is the reason even dealerships don't. batteries are complicated. electricity is complicated. there aren't any specialists out there, and they depend on machines to tell them things, which doesn't always work.
    just so you don't feel alone, i started my prius in the summer of 2018, drove 4 miles, left it for an hour, and when i tried to start it again, the 6 1/2 year old battery measured 4.4 volts :)
     
    #11 bisco, Mar 24, 2023
    Last edited: Mar 24, 2023
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  12. ChapmanF

    ChapmanF Senior Member

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    I thought it is out under the hood in Gen 4.
     
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  13. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    It is under the hood but it was tucked in the corner with little room around it and it seemed the tech had difficulty reaching the bolts holding it in place.

    20230323_150039.jpg
     
    #13 PriusRos, Mar 24, 2023
    Last edited: Mar 24, 2023
  14. bisco

    bisco cookie crumbler

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    right. i have read they are still more difficult for some reason, and now gen 5 is back in the hatch to make room for a bigger engine.
     
  15. CA Guy

    CA Guy Junior Member

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    That's surprising. I am just a regular joe and I was able to swap out my dead Gen-4 12v battery in 10 minutes.
     
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  16. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    You must know the secret. I think the guy didn't know how to reach the bolt and had the wrong socket wrench to begin with. Then he dropped the bolt. It probably wasn't that difficult as he made it look!
     
  17. ChapmanF

    ChapmanF Senior Member

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    Happy news for those of us who wire stuff to it.
     
  18. bisco

    bisco cookie crumbler

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    i don't, but i've always been fine with it in back. sure keeps it looking new.

    i had hoped moving it to the engine bay would have allowed toyota to put a $100. battery in there, but such was not the case.
     
  19. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    What do you wire to it?
     
  20. PriusRos

    PriusRos A Fairly Senior Member - 2016 Prius Owner

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    Mind you, after his first helper kept bringing him different wrenches, one or two at a time, and nothing seemed to fit (either the wrong size for the bolt or the wrong fitting for the extension piece, or both), I told them I should have brought my wrenches with me. I'm sure I have something that would have fit.
     
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