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Help diagnosing HV battery issue on 2006 Prius

Discussion in 'Gen 2 Prius Main Forum' started by pauljus, Jan 3, 2018.

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  1. pauljus

    pauljus New Member

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    Hello all,

    I'm a new member to this community. Thank you for maintaining such an active and knowledgeable forum! I've learned a lot in the last few days (special thanks to @bisco for his/her insights regarding battery issues)

    I have come across an issue with my 2006 Prius (140,000 miles). I started the car last Sunday after about 1.5 weeks of not driving it (it was garaged during that time) and got the Master Warning, Check Engine Warning, and Brake System Warning lights. After about 20 mins of driving the Brake System light went away however the other 2 lights stayed on. Those lights have stayed from since Sunday til yesterday (Tuesday) when I took it to a Toyota dealership for diagnostics. Here are the following codes:

    -B1421, B1650, C1241, C1242, C1300, U0100, P0A80, B1442, P3000, U0111, B1660

    They told me the HV battery is failing and I need to have it replaced. They quoted around $3600.

    Now what's got my scratching my head is that the tech said they tried to clear the codes after the diagnostics, but the lights came right back. But when I got in the car to drive back home and started it, all the lights and went away. And they've stayed away since yesterday.

    My question is this...if the battery is truly failing, would the warning lights come and go (or stay gone as in my case), or would they remain on the dash til the battery is replaced? I guess I'm unsure if this was some weirdo anomaly or if the battery is truly going bad.

    I did check the 12v, it is at a normal voltage. The fuel efficiency has gone down quite a bit - ranges from 30-36mpg. Also, we noticed the battery indicator on the multi function display's Energy Consumption screen doesn't always show the green charging status when we brake the car. The battery level indicator is showing about 3 bars from the top.

    Any feedback you give will be most appreciated.

    Thank you very much!

    -Justin
     
    #1 pauljus, Jan 3, 2018
    Last edited: Jan 3, 2018
  2. bisco

    bisco cookie crumbler

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    welcome!

    just a guess, but it's likely the battery went out of balance from sitting, and came back a bit from driving it.
    might be the perfect time for the prolong battery charger, but others more knowledgeable than me will be along to give you the best advice.
     
    #2 bisco, Jan 3, 2018
  3. pauljus

    pauljus New Member

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    Hi Bisco!

    Thanks for the quick reply!

    Is it normal for the warning lights to show and then disappear the way they did if the battery is failing? Have other had that experience?

    I've read a little on the battery chargers. I'm on the fence about it. My wife drives the car and she lives about 3 hours away from me. I would hate for her to have on-going issues with the car if we went the charger route. But I'd also hate to replace the battery if it was working fine, just suffered a weird hiccup.
     
    #3 pauljus, Jan 3, 2018
  4. bisco

    bisco cookie crumbler

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    normal is not a word we through around loosely on priuschat. what did the 12v test after the car had been off for 4 or 5 hours?
     
    #4 bisco, Jan 3, 2018
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  5. pauljus

    pauljus New Member

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    11.8v in accessory mode, and between 13.8-14.1v with the engine fully on
     
    #5 pauljus, Jan 3, 2018
  6. bisco

    bisco cookie crumbler

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    dead as a doornail. how old is it?
     
    #6 bisco, Jan 3, 2018
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  7. pauljus

    pauljus New Member

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    about 5 years. You're saying the 12v is bad?
     
    #7 pauljus, Jan 3, 2018
  8. bisco

    bisco cookie crumbler

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    it sounds like it. you could try charging it. if it holds, great, but at 5 years, it might make more sense to replace it. 11.8 is not good. we like to put a volt meter on them when the car is off, accessory mode will cause it to come down a tenth or two.
     
    #8 bisco, Jan 3, 2018
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  9. padroo

    padroo Senior Member

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    I'm not saying they are right or wrong but I would have the 12V battery load tested. When the 12 V battery starts going bad strange things happen. You have a lot of unexplained codes you posted, the ones that start with a "B" are body codes, the ones that start with a "P" are
    Powertrain (engine/transmission) The "U" codes are for User Network. Did it have a check engine light on it before you parked it? It's all those codes that make me suspicious. An open voltage check on a battery is not a good test. If you are going to check it yourself, turn the headlights on and run the blower motor and rear defroster and then check it without starting it, this is a more realistic test.
     
    #9 padroo, Jan 3, 2018
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  10. pauljus

    pauljus New Member

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    After I left the dealership yday, it didnt have any dash lights on.

    So you're recommending putting it in accessory mode and running the blower motor (front vent defroster), rear defroster and headlights?

    Sorry, I'm trying to make sure I'm following these steps correctly. Thanks.
     
    #10 pauljus, Jan 3, 2018
  11. pauljus

    pauljus New Member

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    With the car off not in accessory mode it was indicating 12.1v.

    I didn't think 11.8v was that bad in accessory mode with no load.
     
    #11 pauljus, Jan 3, 2018
  12. bisco

    bisco cookie crumbler

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    12.4 is about the minimum with the car off for 4 or 5 hours to remove the surface charge, preferably overnight before touching anything, including the drivers door.
    there is no exact science, but at some point, the computers start going haywire when they don't receive proper voltage.
     
    #12 bisco, Jan 3, 2018
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  13. pauljus

    pauljus New Member

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    Hmm. Is autozone able to check the 12v battery level? Sorry this is my wife's inherited car and this is the first issue we've had to deal with it.
     
    #13 pauljus, Jan 3, 2018
  14. Raytheeagle

    Raytheeagle Senior Member

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    I just changed the 12 volt battery in our 2010 yesterday that was 8.5 years old because I got a 12.33 volt reading the other morning after sitting idle for 2 days:(.

    If you got 12.1 volts after sitting, it is due for replacement ;).

    I also charged our new 12 volt up prior to placing it into the Prius :).

    Good luck and keep us posted (y).
     
    #14 Raytheeagle, Jan 3, 2018
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  15. bisco

    bisco cookie crumbler

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    yes, auto zone will test it for free, both loaded and unloaded, then give you a printout topmost here.
     
    #15 bisco, Jan 3, 2018
  16. pauljus

    pauljus New Member

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    Just checked the 12v again:

    12.2 with the car off, not in accessory mode
    11.9 with the car in accessory mode
    10.6 with headlights, defroster, and blower motor on medium

    Heading to autozone now for their tests
     
    #16 pauljus, Jan 3, 2018
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  17. pauljus

    pauljus New Member

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    So my wife just took it to autozone. They said they can only do a loaded test. It showed 12.4v - he said the battery is at 89%

    He also tested the starter and alternator twice. The alternator passed. The first time he said the starter failed but the car started (he said the tester detected a delay in the start). The second time the starter passed. My wife will send me the print out in a little bit after she gets home.
     
    #17 pauljus, Jan 3, 2018
  18. bisco

    bisco cookie crumbler

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    prius does not have an alternator, and the 'starter' is one of the two drive motors.:unsure:
     
    #18 bisco, Jan 3, 2018
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  19. dolj

    dolj Senior Member

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    You may be lucky and can get away with charging the battery, but I doubt it. Your battery is essentially flat, meaning it is fully discharged at 11.8 V and the load test (which is a relatively light load, btw) pulling it down to 10.6 indicates poor health. The longer that a Pb/A (lead/acid) battery sits in a discharged stage, the more damage it sustains. The Prius charging system is not geared to fully charging from flat and takes a very long time to do this. An external charger does a much better job of this and this gives the Prius a better chance of maintaining at full. Any time a Prius sits for 2 weeks or more it should be on a maintenance charger.

    You clearly do not understand 12 V battery chemistry (no offence intended, just calling it how I see it), so take it from those that do, just bite the bullet and replace that 12 V battery with a new one. The one from the dealer is a good option if you can get a good price, shop around. You can get an Exide, who have a drop in replacement. Make sure whatever you get, it is an AGM, which will be more expensive than a standard flooded lead/acid.

    Given that your wife is at a distance, you don't want the continued hassle trying to problem solve from a distance. Replace the battery and be done with it.

    Lastly, ensure the battery is fully charged before you take delivery of it, if you do not have a charger to charge it yourself before installing it. Do not take a new AGM battery that is less than 12.9 V.

    Here is a chart that gives a voltage to percentage state of charge (%SoC) FYI:
    Pb:A voltage band (SoC).jpg

    The top line is close to an AGM; the bottom line is closer to standard flooded lead/acid.

    Hope that helps.
     
    #19 dolj, Jan 3, 2018
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  20. pauljus

    pauljus New Member

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    hmm, well now you know how completely unfamiliar we are with this car!

    Actually my wife misreported. Autozone test showed 12.55v, 89%

    Bad battery or not?
     

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    #20 pauljus, Jan 3, 2018
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