What charges the 12 volt battery?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by shells2skis, Oct 24, 2016.

  1. shells2skis

    shells2skis Junior Member

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    I have a 2007 with 130,000 miles. Hybrid battery replaced at 109,000. Last oil change at 129,000 replaced transaxle fluid and rear brakes adjusted. Drove 109 miles at night parked for about 45 mins, then drove 109 miles at night. Parked for about an hour. Started car and everything zeroed out. Trip a, trip b, radio stations, window, and reverse beep all went to default settings. Has reset now 3 times. At one point check engine light came on then turned off. No lights are on except ready. Had the 12 volt measured. Came out to 12.58 and 12.55 under load. Store said battery was good and even had me watch on the recheck. I thought it was the 12 volt due to the reseting everything back to default. Can't think of anything else. The guy at the store said to check the alternator but there is no alternator to check. So, what charges the 12 volt?
     
    #1 shells2skis, Oct 24, 2016
  2. andrewclaus

    andrewclaus Active Member

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    There's a DC/DC converter in the hybrid inverter assembly. The voltage at the battery should be around 14 V when the car is "ready." It sounds like the 12 V battery is probably okay.

    You should be able to retrieve the code stored in history with a Mini VCI and Techstream software.
     
    #2 andrewclaus, Oct 24, 2016
  3. exstudent

    exstudent Senior Member

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    How old is the 12V battery?

    Maybe a loosening grounding bolt that connects the negative cable to the body?

    Don't forget to check the engine oil level regularly too.
     
    #3 exstudent, Oct 24, 2016
  4. shells2skis

    shells2skis Junior Member

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    Bought the 12 volt August, 2014. And had it checked today. Oil was just changed October 10th. Drove 1000 miles since.
     
    #4 shells2skis, Oct 24, 2016
  5. shells2skis

    shells2skis Junior Member

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    Bought the 12 volt August, 2014. And had it checked today. Oil was just changed October 10th. Drove 1000 miles since.
     
    #4 shells2skis, Oct 24, 2016
  6. shells2skis

    shells2skis Junior Member

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    Can anyone think of what else I should check? Since no warning lights are on?
     
    #5 shells2skis, Oct 25, 2016
  7. DonDNH

    DonDNH Senior Member

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    I'd still suspect the 12V battery. Was it replaced with an OEM battery or a discount stores? Was there a warranty on the replacement?
     
    #6 DonDNH, Oct 25, 2016
  8. shells2skis

    shells2skis Junior Member

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    Not a Toyota battery. It is under warranty until August, 2017.
     
    #7 shells2skis, Oct 25, 2016
  9. andrewclaus

    andrewclaus Active Member

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    I agree the ground connections at the battery are a good place to start. Also look at the positive side for signs of corrosion or loose cables, and check torque of the terminal bolts. I found one really loose one time, just hand tight. You'll need to do some minor disassembly to get to it.

    Even though no warning lights are on, there could still be DTCs recorded.
     
    #8 andrewclaus, Oct 25, 2016
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  10. shells2skis

    shells2skis Junior Member

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    I'll check it. Thanks.
     
    #9 shells2skis, Oct 25, 2016
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Look for a loose 12V battery cable, in particular where the ground cable mounts to the body as well as the two cables where they attach to the battery.
     
    #10 Patrick Wong, Oct 25, 2016
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  12. shells2skis

    shells2skis Junior Member

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    Thanks for all the knowledge!! We reinstalled the battery and so far no problems. Fingers crossed.
     
    #11 shells2skis, Oct 27, 2016
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