Replace 12v Battery?

Discussion in 'Newbie Forum' started by Caleb2007, Jun 30, 2019.

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  1. Caleb2007

    Caleb2007 Junior Member

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    Long story short... Randomly getting about 38mpg instead of my normal 46mpg in my 2007. Been doing trouble shooting and wondering if it could be my 12v. 12.1v initially, then I do the soft start thingy and I get 11.9v. I leave the lights and AC on for 5 minutes and it goes down to 9.9v. This indicate a weak battery? Perhaps the reason for my mpg dip? The HV battery is new with only 14000 miles on it.
     
    #1 Caleb2007, Jun 30, 2019
  2. jb in NE

    jb in NE Senior Member

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    Yes.
     
    #2 jb in NE, Jul 1, 2019
  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    #3 JimboPalmer, Jul 1, 2019
  4. Caleb2007

    Caleb2007 Junior Member

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    I talked with a toyota dealer mechanic and he didn't seem to think it going down to 9.9 was an issue. "It's a small battery and is going to drain when used with no charge coming to it." Also, this morning I went through a car wash and while i was in neutral it started beeping at me and giving me the caution triangle telling me to put it in park so it could charge the battery. I got out of the car wash and put it in drive and it all went away. Is that normal?
     
    #4 Caleb2007, Jul 1, 2019
  5. bisco

    bisco cookie crumbler

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    welcome!

    how many miles on her?

    how old is the 12v?

    is the battery really new, or remanufactured?
     
    #5 bisco, Jul 1, 2019
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    For a definitive test use an electronic load tester, either DIY with something like Solar BA5*, or check with automotive retailers selling batteries: they're likely to have a pro-level tester and will test for free. Dealership can test too, likely charge $50~100 though.

    * See Solar BA9 on amazon, a bit cheaper too. Hey, 9 has to be better than 5?
     
    #6 Mendel Leisk, Jul 1, 2019
  7. Caleb2007

    Caleb2007 Junior Member

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    Bought the Prius about 3ish months ago. It had 95k on it, and it now has almost 98k. The previous owner had a local shop put a new HV battery in 2 years ago. I have no idea about the 12v battery. Dealership says about $350 for battery and install. I can install, I've already opened up the back all the way to do some troubleshooting myself. I just keep getting mixed answers about the 12v being the problem or not.
     
    #7 Caleb2007, Jul 1, 2019
  8. Skibob

    Skibob Senior Member

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    That beeping thing is normal. The Prius cannot charge the traction battery when the car is in neutral. Where you in a car wash that required you to be in neutral? Is so then you should basically turn off everything that uses power while you are in neutral, especially the AC. Just put the fan to a lower speed and suck it up for the 2 minutes. Turn off the radio and headlights if they are on too.
     
    #8 Skibob, Jul 1, 2019
  9. Caleb2007

    Caleb2007 Junior Member

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    Bought the Prius about 3ish months ago. It had 95k on it, and it now has almost 98k. The previous owner had a local shop put a new HV battery in 2 years ago. I have no idea about the 12v battery. Dealership says about $350 for battery and install. However, I can install it if need be as I've already opened up the back all the way when I did my own troubleshooting. I just keep getting mixed answers about the 12v being the problem or not.
     
    #9 Caleb2007, Jul 1, 2019
  10. Skibob

    Skibob Senior Member

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    Try cleaning your battery terminals and posts.
     
    #10 Skibob, Jul 1, 2019
  11. bisco

    bisco cookie crumbler

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    you can't put a prius through a carwash that requires neutral, it drains the hybrid battery
     
    #11 bisco, Jul 1, 2019
  12. jb in NE

    jb in NE Senior Member

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    I would pass on that good deal...
     
    #12 jb in NE, Jul 1, 2019
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  13. fotomoto

    fotomoto Senior Member

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    Better define "local shop" and "new HV battery" because a lot people call a rebuilt/refurb HV battery new but it's not.
     
    #13 fotomoto, Jul 1, 2019
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  14. bisco

    bisco cookie crumbler

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    most techs don't know how to diagnose a 12v. that comes from years of trying to crank the engine, and determining by the sound if the battery is weak.

    tbh, you're voltage is sketchy, i would replace it.
     
    #14 bisco, Jul 1, 2019
  15. bisco

    bisco cookie crumbler

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    you need to get documentation of the 'new' hybrid battery. it could well be newly rebuilt and currently dying
     
    #15 bisco, Jul 1, 2019
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  16. Caleb2007

    Caleb2007 Junior Member

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    I have documentation of the receipt for the battery and installation, but I can't find where it says what kind/where the battery is from. It just says that one was installed for $2000 including tax and labor. But I do know that the previous owner told me that he didn't want the battery to be a used one for the same reasons you are all telling me to stay away from used batteries, so he specifically got a "new" one. Unfortunately I forgot to take a picture of the physical battery when I opened up the back to check the HV fan (which was not gunked, just dirty and air would still be able to flow through it).
     
    #16 Caleb2007, Jul 1, 2019
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  17. sam spade 2

    sam spade 2 Senior Member

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    He is a fool and doesn't deserve the title "mechanic".
    10 volts is just a hair away from stone cold DEAD.
     
    #17 sam spade 2, Jul 1, 2019
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  18. fotomoto

    fotomoto Senior Member

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    New Toyota batteries were not $2k installed two years ago. Chances are very high it's aftermarket (used). Shops market them as new.
     
    #18 fotomoto, Jul 1, 2019
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  19. Caleb2007

    Caleb2007 Junior Member

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    Wait. I just remembered I tried calling the number on the battery case when I had it all opened up. Calling it I found it was Dorman Products. So with a little more investigation I believe it must be what I found on their website. (I can't link it since I have yet to be on the forum for day and a mod has to continual approve all my posts.)
     
    #19 Caleb2007, Jul 1, 2019
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  20. Caleb2007

    Caleb2007 Junior Member

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    Well, it was being used without the engine running with AC and lights. (Again, I'm no mechanic, but a 12v is a small battery and is bound to lose power right?)
     
    #20 Caleb2007, Jul 1, 2019
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