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Cannot figure out what is wrong....electrical issue...

Discussion in 'Gen II Prius Main Forum' started by NickBaker9, Sep 11, 2012.

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  1. NickBaker9

    NickBaker9 Junior Member

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    SHOCKING that this car would have an electrical issue. OK, so here is what happens, and I've posted about this before, but I want more opinions. So when it gets hot out and I leave the car in the sun it just dies. I have to open the car with the key (I have the keyless entry with nav and all the bells and whistles on this car and I LOVE it except for this issue...) and get in, open and close the door a few times, then the alarm goes off, I push the power button, then the car will sometimes go right to ready and sometimes act like I'm not pushing the break for the one push, ready to go feature. As you can tell, I'm not tremendously well versed in this stuff, but I have replaced a headlight, and if I need to, I've found a junked battery for $50 and can replace it on my own, I'm just not convinced it's the battery. The car was in an accident about 9 months ago and I noticed right after I got it back from the body guy that it would sometimes erase all my presets with the radio and wipe the previous places in the nav, as well as reset the clock. All just annoying. I just have no idea why the heat plays a factor in this...that's the variable that doesn't make any sense with the battery. The year is 2006 and it is the original battery. I tested the battery with the internal battery thing with the car off and it was at 11.9 V and 14.5 V when on. Please help!
  2. NickBaker9

    NickBaker9 Junior Member

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    And this problem has gotten progressively more frequent with the heat and with time...because I live in LA and it's been pretty hot.
  3. uart

    uart Senior Member

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    Those problems do sound like they're related to the 12V system.

    - Check that the battery terminals are corrosion free and correctly tightened.

    - Check that the "pig-tail" where the battery -ive connects to the body is also tight and corrosion free.

    - Check the battery voltage under load. Make sure that you at least place the Prius in the Ig-on state (but not the "ready" state) when you are measuring the battery voltage. If the 11.9 volts was measured in "accessories" mode then that battery is definitely too weak. Also, make sure you test the battery after the car has been sitting (off) for at least a few hours.
  4. John H

    John H Senior Member

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  5. cwerdna

    cwerdna Senior Member

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    OP had already posted earlier at HELP!!! Prius sometimes won't start, will after I fidget with it. | PriusChat.

    What are the voltages at all steps of the test, AFTER the car has sat overnight? There's at least 1 number missing. I already posted what I thought about seeing 14.5 volts in READY on the bus in the other thread.

    Patrick Wong, myself and a whole bunch of others have told him his 12 volt needs replacement. I replaced mine on my 06 over a year ago.

    And, he's stated "And I think someone asked if I left lights on. I do, on occasion..."

    Don't buy a "junked battery for $50". What makes you think that it's in good condition and able to properly hold a charge?
    John Hatchett likes this.
  6. uart

    uart Senior Member

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    LOL, it looks like Julia missed an opportunity to make a quick $50 with her old battery. ;)

    Regarding the high 14.5 volts at ready. Yes I agree this is indicative of a higher than normal internal resistance (and so probably an unhealthy battery).
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  7. edthefox5

    edthefox5 Senior Member

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    Who in his right mind would install a junked $50 battery chasing a bad battery problem?
    This is just a troll breaking our chops.
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  8. NickBaker9

    NickBaker9 Junior Member

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    If it's a 2009 12v and it costs $50, versus $200 for a new one, do the math. It saves money over time, even if I have to replace it 4 times, which won't happen while I own the car. That said, why would you see a 5mpg improvement with a new 12v? Sounds intriguing. I'm not trolling, I'm just an actor trying to save money. $50 versus $200...especially if I'm not 100% convinced that it's not a short somewhere in the system. Just being pragmatic...and somewhat cheap...lol.
  9. cwerdna

    cwerdna Senior Member

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    You're wasting time if the $50 battery is shot and/or has been run flat numerous times. It might not do you any good right off the bat or need replacement within a few weeks.

    It also could be the wrong size. Non-SKS (Smart Key System) Priuses have a smaller battery than SKS equipped ones. I'd imagine ones w/no-SKS don't need as much capacity since there's less parasitic drain when there's no SKS.

    Closed Minds | PriusChat was a post about a clueless dealer running Prius 12 volts flat.

    If you're going to subject your 12 volt to deep discharges by running it flat, supposedly the Optima Yellow Top handles it better.

    I still don't understand why you think it's a short in the system. Everyone else in the other thread says to replace the 12 volt. It's at end of life, or beyond. And, you still haven't told us all 3 voltages. I bought my 06 in January 06. MY 12 volt was getting marginal over ago, so I replaced over a year ago.

    Seilerts posted his disappointment about the stock 12 volt at 12V battery autopsy | PriusChat. Unfortunately, the original image got busted due to the Priuschat software switch. A smaller version is his avatar.

    As I said earlier


    Anyone that has a decent amount of technical knowledge about the Prius can confirm this.

    Also, at this point (due to the 12 volt's age), don't waste money and time having the dealer "test" the battery. More than once, we've found whatever "test" they do to be a waste of $ and to be useless. Example: 07 Prius Dead - Any Guesses? | PriusChat
  10. uart

    uart Senior Member

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    Nick, your $50 battery may be an ok buy if it turns out to be in good condition. Did you get it from a wreckers/dismantler? Have you tested that takes a charge ok and retains its voltage? If so, then you should use it to replace your existing battery and see if it makes any difference.

    BTW. Could you please make sure that you've tested your present battery properly, so that you have something to compare to. Just make sure that the car has been completely off for at least several hours and then place it into "Acc" and then "Ig-on" mode when you measure the service menu displayed voltage.
  11. John H

    John H Senior Member

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    It seems that when the 12V is failing the vehicle spends more time running the ICE and consequently reduces the MPG. One of the common symptoms of a 12V failing in a genII is an unexplained drop in MPG.
  12. edthefox5

    edthefox5 Senior Member

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    Ok not a troll but please realize replacing a 12 volt battery in this car is alot harder than most cars and is dangerous and your exposing the car to its fatal flaw. The dreaded reverse polarity hook up. That can kill this car and cost you $4000 in repairs. I know this mistake could be hard to do but it would not surprise me. Your an actor not a mechanic.

    Quit mucking around and put a new battery in this car. Move on.
  13. R-P

    R-P Member

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    I do not know the specifics of the Prius radio, but if the memory of the radio is wiped, but he manages to start his car, there's more to it than a weak 12V battery: there might very well be a connectionproblem somewhere.
    Most carradio's should not loose their memory even if it drops to 9 volts. And if the Prius battery drops to 9V, there's no way you will ever get it going without charging the battery first. Well, this is at least my assumption from reading stuff about Prii in here.

    BTW: 30-40$ will get you a new motorcycle battery at some places. And although I would never advocate using a different, ill-fitting battery, I would easily prefer this option over buying a second hand one...
  14. John H

    John H Senior Member

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    Not positive on this but ... YMMV ... when you turn the Prius to "Ready" a charging circuit supplies 13V+ to the 12V battery from the traction battery. This can be enough to start the Prius and get going but the charging circuit will continue to try to juice up the 12V battery the entire time, without much success and additional drain on the traction battery, causing the ICE to run longer (and thus the lower MPG).
    KK6PD likes this.
  15. ahmeow

    ahmeow Prius Lover

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    Especially you did mention your car had an accident yrs before and after that something wrong. So it's not "THIS CAR IS HAVING AN ELECTRICAL PROBLEM". It's your mechanic or the body shop did a not perfect job. You don't get the advise of us and still argue. Your problem will continue. Consider our advise.
  16. R-P

    R-P Member

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    John Hatchett: not sure if you were replying to me or commenting on the 5mpg improvement.

    Turning the Prius to "ready" requires a substantial current from the 12V circuit.
    I made a 14.4V lithium battery capable of supplying >1A and it did NOTHING to get the car going after the wife left the lights on... When discussing this on here, I was told a number of up to 20 amperes is needed to get all relais and other 12V stuff working, and THEN the big 100A 13.8V inverter will start helping out in the 12V circuit. But before that happens, it's all up to the little 12V battery.

    BTW: I did make a custom 'startercable' after this incident because the wife complained her collegue could hardly put his 12V startercable clamp on the starter-connectionpoints under the hood. Small 50A clamps and 13Ga speakercable.
  17. John H

    John H Senior Member

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    Sounds correct. The difference may be a "bad battery" versus a "drained battery".

    A "bad battery" may be able to supply 20amps at 11V while a "drained battery" may not.
  18. cwerdna

    cwerdna Senior Member

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    Agreed. We've seen and heard of people reversing the polarity when jump starting (for some bizarre reason) and blowing the inverter, which has a 4 digit price tag.


    I forgot about he accident. That is troubling too. But the 12 volt is what I consider end of life, by age. OP still hasn't supplied us w/a complete set of voltages after the car has sat overnight. To me, the 12 volt is questionable from what we know so far.

    If the 12 volt battery were brand new and all voltages looked good after the car has sat overnight, then we could rule out the 12 volt battery. We definitely can't right now.


    Problem is voltage can dip pretty low at various points, right when trying to "start" the car and during the the evap leak check (begins 5 hours after power off, runs for an unknown amount of time).
  19. NickBaker9

    NickBaker9 Junior Member

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    Clearly I was not providing enough info...so here are some readings. I just tested the battery at 2 am. I last drove it at 515 pm. More than ample time for powering down. The battery reading with no components on was 12.2v. Then I pressed the power button on to put it accessory mode and it went to 10.6v and went up and down by .1 for a minute or so. Then I turned the car completely on and it went to 14.9v. So, from what I'm gathering, those readings aren't amazing, but I don't really think they point to a failing battery, do they?
  20. NickBaker9

    NickBaker9 Junior Member

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    Actually, I'm pretty sure they do not. So in case I'm right, I'm back to where I'm started in that somehow, heat has something to do with this puzzle. The one thing I have always noticed is that heat somehow causes it. It hasn't been hot out and I've parked the car in the shade at it hasn't reset in over 2 days. I think this has more to do with everything than the battery...anyone else agree? What on EARTH could this be? The nice thing is that I have a limited warranty on it still for another 12k miles or so, so no rush, but I want to make sure before I go taking it to someone. Anyone know of a good HONEST Prius mechanic in Central LA? Close to Hollywood?
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