Help... new 12volt, now car won't start

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by LTH1973, Aug 28, 2012.

  1. LTH1973

    LTH1973 New Member

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    Hello,
    My wife was driving the 2009 Prius today, 2 hours away, and she left the lights on after she had parked it. It killed the battery. AAA came to jump it but nothing worked, won't start. AAA came back with a new battery, installed it and still nothing. The green light on the ignition turns on, then a check engine light but thats it. The car wont start. Now my wife and my car are stranded. A Toyota guy said that he thinks changing the battery leaves the car needing to be reprogrammed? What?? Has anyone had this problem. Is it just something that needs to be reset. Help!
     
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    You can try disconnecting the 12V battery negative cable where it bolts to the body for a few minutes, to allow the ECUs to reset. However, I doubt that will help.

    You'll probably need to pick up your wife and have the car towed to your local Toyota dealer for help. It is possible that the jumpstart may have been botched (reverse polarity applied) which at minimum would cause a fusible link to blow and worst case may require inverter replacement.
     
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  3. edthefox5

    edthefox5 Senior Member

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    Oh god not another AAA reverse jump started the car. Not sure how those guys mess up what is so easy to do.
    Not to scare you but if the car is jumped started improperly by reverse polarity on the leads it sometimes causes major damage to the electronics in the car and we have seen alot of this in the last 5 years. Alot. Worst case scenario is the Inverter is toast.

    Get ready to put a claim against AAA for this. Get the tech's name.

    Start checking fuses. There's fuses in the black plastic fuse box under the hood to the right of the Inverter. There's also a 100 amp fuse mounted on top of the 12 volt battery itself in the trunk. Its in the black plastic module on the + post.
    And there's fuses in the kick under the dash.

    But I think you'll end up getting it towed to a Toyota dealer.
     
  4. edthefox5

    edthefox5 Senior Member

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    Hey Pat instead of unbolting the neg lead can't you just unplug the pos lead thats plugged into the pos post fuse assy?
    Unplugs very easy there.
     
  5. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Hi Ed,

    I haven't tried that, and that also would be a reasonable approach.
     
  6. edthefox5

    edthefox5 Senior Member

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    It occured to me when I put my Optima in 2 weeks ago. Its real easy to just unlug the main B+ lead there at the battery.
    There's another smaller lead that unplugs too. Do not know what that powers. I think its a keep alive for the Hybrid battery relay circuit??

    All the battery replacment tutorials never mentioned this plug and I saw that it was unplugable. Nice byproduct of unplugging that is no arcing or sparks when you bolt the neg lead back on.
     
  7. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

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    I have left Prii batteryless for extended periods of time without ever having had to do reprogramming as a result. I have also had AAA jump start one of my Prii backwards. After taking it to two different DEALERS neither one wanted admit the damage to my Prius was related to being jump started backwards. For some reason, certain people on this forum only recommend others take their Prii to dealerships as opposed to qualified independent repair shops like mine. If by chance you are in the Los Angeles I would be happy to help. Otherwise, if you could update your location I will see if I can find someone near you that can help.

    Avi
     
  8. Patrick Wong

    Patrick Wong DIY Enthusiast

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    There is a small fuse for the 12V battery sense circuit, which allows the inverter to see what the battery voltage is.
     
  9. edthefox5

    edthefox5 Senior Member

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    Ok thanks.
     
  10. PriusCamper

    PriusCamper Can a Prius be a Campervan?

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    It seems strange that they'd design an electronic system that could be so severely damaged when it's jumpstarted in reverse polarity? I mean what's the specific design limitation that makes such damage unavoidable? Why not just put some kind of breaker in that protects the car?
     
  11. edthefox5

    edthefox5 Senior Member

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    Oh boy here we go:p
     
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  12. Patrick Wong

    Patrick Wong DIY Enthusiast

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    The DC/DC converter within the inverter typically is destroyed when reverse polarity is applied to the battery. To prevent that, a diode at the DC/DC converter output would be required.

    One possibility is to connect the cathode of the diode to +12V and anode to ground. That diode would only operate under reverse polarity conditions. It would have to have sufficient current capacity to short the current provided by the jump battery without blowing up, up to several hundred amperes.

    Alternatively, a series diode could be used. This diode would conduct under normal operation and block negative voltage from entering the DC/DC converter output.

    However a silicon diode would introduce 0.7V voltage drop. The output of the DC/DC converter can be up to ~100A, so use of the diode would result in up to a 70W power loss. The DC/DC converter would also have to be set up to run 0.7V higher than it currently runs at (13.8VDC) to make up for the diode voltage loss.

    A circuit breaker would not be helpful, considering the normal power output. A breaker that trips at 100A provides more than enough power to short out the DC/DC converter output transistors when reverse polarity is applied.
     
  13. uart

    uart Senior Member

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    Good point Avi. It's totally frightening how often people seem to report some kind of major problem immediately after a jump start. There's no way that this should "spontaneously" happen in a car that was running perfectly and just had the lights left on. There pretty much has to be something gone awry with that jump.
     
  14. Britprius

    Britprius Senior Member

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    A 25amp or greater diode (stud type) in series with the jump point would allow sufficient current for a jump start but would not allow current flow if the jump polarity was wrong. One could also be fitted at the battery +terminal for a direct jump. The voltage drop in this situation would not matter These terminals would not need to be insulated as no current would flow back through the diode if by accident it is grounded.
     
  15. uart

    uart Senior Member

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    Hopefully LTH1973 will let us know what it turns out to be. It may help other users facing similar jump start issues.
     
  16. PaJa

    PaJa Senior member

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    The unplug of 12V battery is a rutine step for the car maintenance. Nothing serious will happen, just to re-programm FM radio. Sometimes the power windows calibration is needed, but it depends what task is was done. The basic car ECU diagnostic (health check) will tell you what condition for the start are not met. To call Toyota assistance or nearest dealer will be be the best option.
     
  17. NinnJinn

    NinnJinn Member

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    Does "reverse polarity" mean Positive jumper on negative post and Negative jumper placed on positive post?
     
  18. Avi's Advanced Automotive

    Avi's Advanced Automotive Independent hybrid repair shop

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    Yes!
     
  19. NinnJinn

    NinnJinn Member

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    *going outside to check under the hood to see what is so hard about properly jumping a prius!!!*


    15 minutes later.... After searching under the hood, I looked in my owner's manual. I don't have an access point under the hood. If I need a jump in my 2002, you have to go to the trunk and jump the battery itself.
     
  20. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Yes. A hood access point is not really needed because it is usually not very hard for you to open the Classic trunk.

    With 2G, if the 12V battery is dead, the hatch can only be opened via a process that requires you to crawl into the hatch area, remove items in the way, remove the folding hatch floor, find a little rectangular opening in the black plastic tray over the spare tire, and reach through to move a little lever to open the hatch lock.

    Since this is an irritating process especially if your hatch area is occupied, an alternative is to use the jumpstart terminal in the main relay/fuse box.
     
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