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Prius will NOT shut-off, MDF stays on

Discussion in 'Gen 2 Prius Main Forum' started by overlap, Sep 25, 2010.

  1. overlap

    overlap Junior Member

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    Hi. My 2008 Prius will not fully shut-off and the MFD LCD display stays on showing the "empty" or all-white battery as seen in an accessory mode. Also when the prius is on and drivable, the power button light is OFF. The power light is green in (1 of 2?) accessory modes, and orange in the other.

    This happened after having a mostly dead 12v battery, using a 10-40 amp battery charger on the positive 12v post in the fuse box and negative on the shock tower stud. (Never was there a reversed polarity.) But, the Prius kept popping the 40 amp fuse several times until 5 minutes later there was enough power to start the car. But during this time I was pressing the Power button very rapidly, because I was late for a dentist appointment :).

    What the heck is wrong? What a piece of junk if once cannot simply give a car a jump :) Very frustrated.
     
    #1 overlap, Sep 25, 2010
  2. okiebutnotfrommuskogee

    okiebutnotfrommuskogee Senior Member

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    We will leave the accurate diagnosis to some of the more knowledgeable folks here, but it sounds like a bad 12 volt battery to me. I would have charged the battery only at the battery posts, and only at 10 amps. It's a little battery.
     
    #2 okiebutnotfrommuskogee, Sep 25, 2010
  3. overlap

    overlap Junior Member

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    That is easy for me to say too in hindsight. It really is a 10 AMP charger with a 40 amp starter boost.

    The 12 volt battery is no longer the issue as it is charged, a battery maintainer is on it, and the voltage is at a constant 13 to 13. 6v.

    Does anyone know about the actual symptom?
     
    #3 overlap, Sep 25, 2010
  4. David Beale

    David Beale Senior Member

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    The symptoms are the battery is no good. Just because you measure some level of voltage on it doesn't mean it's good. Get it checked with either a pulse tester or a load tester. Make sure the user of the load tester doesn't exceed 100 Amps and do connect directly to the battery for the tests, with the car disconnected (disconnect the -ve terminal lead from the body for example). Further warning, when you reconnect the battery to the car there will be a healthy spark. There are a bunch of large capacitors in there.
     
    #4 David Beale, Sep 25, 2010
  5. overlap

    overlap Junior Member

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    Somehow the car is now back to normal after fiddling with it in many ways. What the problem was like was that the 3 or more "modes," normal-on, accessory1, accessory2, other?, was just out of wack and order, and the corrrect Start button light. When the car was drivable, the orange light stayed on. Getting the car drivable took as many as 10 tries cycling thought this nonsense. 50% of the time either or both the dash warning or a warning in the upper left corner of the MFD shown. There were no error codes seen on the ScanGaugeII.
     
    #5 overlap, Sep 25, 2010
  6. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Unless you really want to damage the Prius electronics, do not use a charger set to the 40A "boost" position. Think about what is required to get the 12V battery to accept a 40A charging current: the charging voltage has to be excessively high, perhaps 16V or more. That probably confused the car's electronics, and you are lucky that application of that voltage did not cause permanent damage.

    Now that your immediate emergency is over, I suggest three items for your consideration:

    1. Buy a new 12V battery now, so that this drama won't repeat itself in the near future.
    2. If in the future you have a similar problem, it would be best to charge the battery using 4A or less of charging current.
    3. If you believe you have an emergency, feel that fast results are required, and you don't have another vehicle to use as a 12V source, then you need to disconnect the 12V battery from the Prius before you attempt to use a "boost".

    Keep in mind that since the battery has a warning label that requires you not to use more than 4A charging current, that you are taking some risk that the battery may explode as excessive current is applied to it.
     
    #6 Patrick Wong, Sep 25, 2010
    3 people like this.
  7. Mr.Vanvandenburg

    Mr.Vanvandenburg Active Member

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    Blowing 40amp fuses, which I take means more than one, sounds, in highest engineering terms, pretty awful. I use the Prius as more of an appliance, too expensive to not follow the instructions exactly. Hope you are back to normal.

    I was in a big hurry getting gas once, don't know what I did wrong, but the car wouldn't start after filling, and the key symbol was on. I tried over and over, with someone behind me waiting. Finally used the slot and it worked. Since then no more probs and the battery in fob checks out OK.

    I wouldn't blame the Prius and call it junk for this.

    p.s. I am on a fixed income and retired, this car was lot of money for me in 07. I am not about to mess with the electrical system on a Prius, of all things not to mess with electrical, it would be on a Prius. (Read some of your other posts.) I don't even use the mfd screen except once in a while to check how I am doing with mpg. I would like an oil pressure and temp gauge, with dials with needles though.
     
    #7 Mr.Vanvandenburg, Sep 25, 2010
  8. vertex

    vertex Active Member

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    Sounds like the 40A boost scrambled the CPUs. Probably disconnecting the battery ground for a few minutes would have reset it. Glad you are up and running. Run the battery diagnositics. If not OK, repalce the battery, and/or if the battery dies again, replace it.
     
    #8 vertex, Sep 25, 2010
  9. overlap

    overlap Junior Member

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    I'm surprised about such different experiences or devices. My particular Schauer 10 amp battery charger has no switch on it. With a battery at 13v, it is impossible for it to put out 40 AMPs. I have years of experience with it. (This Prius is a small fraction of the cars I have owned and tweaked.) It is fully automatic and only puts out more amps as the voltage drops. As stated, the factory Prius battery maintained 13v with the car ON, no shortage of power, and able to drive. (With the Schauer 1.5 amp battery maintainer in parallel until the factory DC-DC converter maintains the factory 12v battery (with it's max 80 factory AMPs IIR.)

    I have battery load tester, but there is simply no need to use it if voltage does not drop when a load is placed on the battery.

    That said, I do want to get as good of a 12v battery as I can. Does anyone know of the biggest and best battery that will fit in the factory spot? I have not looked to see if bypassing the factory battery hold-down could then fit a bigger battery. I am willing to do light fabrication such as grinding away brackets, etc, especially of someone has already engineered the best including a hold-down.

    Has anyone optimized (no pun for an Optima) the highest quality and largest capacity battery to fit in the factory Prius spot?
     
    #9 overlap, Sep 26, 2010
  10. seilerts

    seilerts Battery Curmudgeon

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    I'm happy with the Optima that I got from elearnaid.com.
     
    #10 seilerts, Sep 26, 2010
  11. derkraut

    derkraut Member

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    Am I missing something here? isn't your 2008 under warranty? Take it to a dealer! Putting as charger on it with 40amp boost is absolutely silly, imho.:(
     
    #11 derkraut, Sep 26, 2010
  12. adric22

    adric22 Ev and Hybrid Enthusiast

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    Believe it or not, my Toyota Mechanic buddy was just telling me a story of diagnosing a similar issue the other day. He said it turned out to be an issue with the can bus, I think one of the connectors was loose or something. See, apparently the car will not shut off until it receives the information from one of the computers that the parking pin has been properly locked. When the computer that controls that lost connection to the can-bus, the main computer wouldn't allow the car to shut completely off.
     
    #12 adric22, Sep 26, 2010
  13. richard schumacher

    richard schumacher shortbus driver

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    When the car is ON this is the output voltage of the charging system inverter; it is *not* the 12V battery output. In fact the inverter output should be about 13.8V. If it was 13.0V that indicates a heavy drain somewhere, perhaps a shorted cell in the 12V battery.

    On the whole it sounds like this battery is toast. You can test it accurately using the built-in diagnostic system. The procedure is described here:
    http://priuschat.com/forums/newbie-forum/73400-weird-stuff-happening-mpgs-dropping-test-battery.html
     
    #13 richard schumacher, Sep 27, 2010
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