12V Battery

Discussion in 'Gen 3 Prius Main Forum' started by Mitzie, May 19, 2020.

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  1. Mitzie

    Mitzie Junior Member

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    We just bought and installed a new 12v battery to our 2011 Prius with 205K miles. After installing it last night (2 days after purchasing it), we did the self battery test and it read 11.6. When the engine was turned on, it went to 13.5. Drove it for half an hour and then it sat overnight. Checked it this morning after 12 hours overnight and it says 11.6. I have read from other posts having it around 12-14. Is my battery bad? We’ve only used the car’s self battery test for this. Thanks in advance.
     
  2. AzWxGuy

    AzWxGuy Weather Guy

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    Yes, 11.6 volts is way too low. The Prius 12 V battery charging routine might take several days to bring it up to full capacity. The fact that your voltage reading when Prius made Ready was only 13.5 volts says the battery is depleted. Normal Ready voltage should be around 14.5 volts. I would take the battery back to where you purchased it and have them test, charge, and test again to demonstrate to your satisfaction that the battery is fully charged.
     
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  3. ETC(SS)

    ETC(SS) The OTHER One Percenter.....

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    Why the new battery? Is it your first?
    Why the two day delay before the install?
    Where did you get the battery and where did you store it for the 2 days?

    You might be fighting an electrical issue caused by 200,000 different things---one for each ownership mile, but if you're having battery issues a good place to start troubleshooting is with a 'known-good' battery which, as @AzWxGuy mentioned above might require a visit to the place that you purchased the battery from.
    Or?
    If this is the first new battery for your '11 you're just about due and you may have bought a battery that sat on a shelf for a while before you walked out the door with it.
    Your car IS BOOTING UP - right?

    You may also want to check your cabin air filter.... ;)
    Your location is non specified, which is GOOD....but I'll betcha they have mieces there.

    Good Luck!
     
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  4. AzWxGuy

    AzWxGuy Weather Guy

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    Yes, as further clarified by ETC(SS). Good idea to check your cabin air filter and make sure you even have a cabin air filter. And while you're at it, make absolutely sure your drivers-side floor mat is properly installed and clipped in. Man, I'll betcha Toyota just hates to have to put that on every service document.
     
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  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Automotive retailers should get into the habit of demonstrating their battery's health before handing it over to the customer. They typically have electronic load testers for this purpose; should use them routinely at point-of-sale.
     
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  6. Grit

    Grit Senior Member

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    Exactly. I always call before hand to let them know I’m coming to buy a particular battery and to have them charge it to 12.7 volts with the most recent month/year affix label. When I go pick up, I measure the 12v bat with own multimeter before paying.

    Lesson, You can leave with a new battery from the store it being low on charge also. You’ll be back in square one again.
     
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  7. Mendel Leisk

    Mendel Leisk Senior Member

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    I bring along a Solar BA5. As often as not they offer to demo-test the battery with their tester, typically a similar, but pro-level tester. These devices test volts but more importantly: Cold Cranking Amps. Regardless of the Prius not needing cranking, the CCA test of the battery is a good measure of it's health.

    A fresh battery in good shape will test well above the rated CCA, say 25~40% higher.

    That they were sold a dud is one possibility. The other, as @ETC(SS) 's already pointed out: the car may be "eating" batteries. The OP will have to clarify the back story.
     
    #7 Mendel Leisk, May 20, 2020
    Last edited: May 20, 2020
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  8. Mitzie

    Mitzie Junior Member

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    Yes thank you! I made an appointment This Friday to have it checked at the dealership where I bought it.

    Thank you! It is my first battery change since 2011, so my first one lasted for 9 years. My old battery started acting up due to the shelter in place and so I wasn’t driving it that much and shortly before SIP, we were gone for a month and didn’t drive it.

    2-day delay was just because of studying and class getting in the way and we didn’t have the right tool for the nuts/bolt. But the battery was in a box inside the house, we never opened it since we bought it, not until we had to change it.

    Yes, my car is booting up and checked the cabin air filter 3 weeks ago and it looks ok:)
    Thanks for the reply!

    Agree. It’s the first time that I have to change the battery & I’m learning from the experience.

    I hope our Prius is not eating batteries. It was bought brand new in 2011 and never had to change its 12v battery till last Monday. We had 9 years of use from the old one which we think just drained because for a month, we were out of the country and then the shelter in place, & so the car wasn’t driven as much as before.
     
    #8 Mitzie, May 20, 2020
    Last edited by a moderator: May 21, 2020
  9. ASRDogman

    ASRDogman Senior Member

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    I take it you got the battery from a Toyota dealership?
    You could just purchase a 4 amp battery charger and charge the battery overnight.
    You can get a decent one for about $30-40.

    Since it boots up the computers and the car runs, you could just take a long drive of 2 or more hours
    and that would probably charge it up.

     
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  10. Mitzie

    Mitzie Junior Member

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    Thanks! Yes, the battery was bought from a dealership.
     
  11. Mendel Leisk

    Mendel Leisk Senior Member

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    All things considered, I think whoever you got the battery from owes you the dealership owes you. A test, a charge, most likely a replacement. Sounds like they sold you a dud.
     
    #11 Mendel Leisk, May 20, 2020
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  12. Johnny Cakes

    Johnny Cakes Active Member

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    11.6 is really very low. Every reply in this thread assumes that this was accurately measured.

    Mitzie, when you say you did the "car's battery self test" what does that mean?
     
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  13. Grit

    Grit Senior Member

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    I ain’t paying for a new battery that’s not up to voltage and then buy a charger for it also :ROFLMAO:
     
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  14. Grit

    Grit Senior Member

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    Theres a way to check 12v on ACC.
     
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  15. Johnny Cakes

    Johnny Cakes Active Member

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    Interesting. Could you be more specific?
     
  16. Mendel Leisk

    Mendel Leisk Senior Member

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    I like to get a good battery, AND then give it an initial charging session. But yeah, it should not be necessity. If it's low voltage at the outset it's likely on the way out, way too long in storage. Again, an electronic load tester, check the CCA, cuts through the fog.
     
    #16 Mendel Leisk, May 20, 2020
    Last edited: May 20, 2020
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  17. Mitzie

    Mitzie Junior Member

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    just the battery check feature of the prius where you turn the power button once without pressing the break then you press info button while you turn the headlight on then off 3x. We don’t have the machine to check it. On Friday, Toyota will check it for me for free

    that’s what toyota said they would do on Friday, test it then charge and we’ll go from there.
     
    #17 Mitzie, May 20, 2020
    Last edited by a moderator: May 21, 2020
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  18. Grit

    Grit Senior Member

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    A fully operating battery from the store will not require an initial charge on your end, plug in play.
     
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  19. ASRDogman

    ASRDogman Senior Member

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    You should ask them why you aren't supposed to charge the Prius battery with no
    more than 4 amps?
    Because I would bet some one will probably put the regular charger on it, and put in 30 amps!
    AGM batteries are charged at a lower amperage.

     
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  20. Mitzie

    Mitzie Junior Member

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    I agree (especially for the price of the battery).
     
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