Some sort of electrical issue?

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by thelonelypuppet, Jan 23, 2020.

  1. thelonelypuppet

    thelonelypuppet Junior Member

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    Hey all. Like I mentioned in my previous post (a while ago), I'm not super familiar with the inner workings of cars and whatnot, so I'll likely describe a lot of my issues in layman's terms.

    So, in the past several months, my 2008 Prius has been acting kind of weird. I had to replace the 12volt battery because it died last summer, I believe, and I got the replacement from O'Reilly's. They told me that the battery was gel-based (I think?) so it would be less resistant to extreme heat/cold, which is what I had been having issues with when the previous battery was on its last legs.

    In that time span, however, I still have been experiencing some weird issues here and there that I also experienced when I was using the dying battery. Here are some problems I've had in the past six-ish months:

    1) I go to open my car door (key in my pocket, so it unlocks automatically). The car sets off a sort of weird "soft alarm" where it's not as loud as a full car alarm--it just honks softly. I think the headlights flash as well. When I turn on the car, the alarm stops.
    2) This usually happens in conjunction with the previous issue. My car will set itself to km/hr instead of MPH. Additionally, it seems to set my odometer to a different setting than normal.
    3) Lately, it doesn't seem like my car is turning on "immediately." It appears to take a few more seconds than it used to.
    4) This problem has happened twice in the past couple of days. I turn on the car, and it goes into a "standby" phase--the light is orange on the power button instead of green. It appears that power is not flowing through the Prius in this phase: the clock is dim, windshield wipers run super slowly, the touch screen doesn't come on, etc. The car stays in that phase for a good minute or so, and it does not respond to me trying to turn it off. Finally, the car shuts off, then when I go to turn it on again, it's completely fine. This happened yesterday afternoon and this morning.

    Again, the 12v battery was replaced recently, and it's still under warranty. My mother was under the impression that the hybrid battery was replaced while she owned it (so between 5-10 years ago at this point).

    A potentially confounding factor is that it did get cold pretty suddenly--probably a drop from 70 degrees F to 50 degrees F. However, I don't think that necessarily qualifies as "extreme cold," which the new battery is supposed to be resistant to, anyway.

    Does anyone have any thoughts about what this might be? Thanks!
     
  2. JC91006

    JC91006 Senior Member

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    Go back to oreilly and have the battery tested, it's free. I don't think 50 degrees is extremely cold either
     
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  3. thelonelypuppet

    thelonelypuppet Junior Member

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    I did earlier today and they said they couldn't test the battery because it needed to be charged first. The battery was still in the trunk and I didn't feel like messing with that tonight, so my husband will be taking the battery out and back up to O'Reilly's tomorrow.

    I'll keep y'all posted for sure. :)

    Edited to add:

    Pulled up the maintenance menu earlier today and watched the voltage on the battery drop from 11.3v (after driving) to as low as 9.5v in the span of 90 seconds. The first time, the car shut off completely and almost had insufficient power to lock/unlock the doors.
     
  4. dolj

    dolj Senior Member

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    Either that battery is toast or you have a serious current drain. I hope it is the battery, cause that is easier to fix.
     
  5. TMR-JWAP

    TMR-JWAP Senior Member

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    The good news is that you now know the problem is due to a weak 12v battery. The next step is to determine the cause.

    The "cause" is usually one of two main things
    1. an internal problem with the battery itself (not likely since this is a recent replacement, but not impossible either)
    2. an external fault putting a continuous current load on the battery while the car is turned off.
    Determining a source of current load when the car is off requires either good EWAG skills or reasonable multimeter/troubleshooting skills.
    EWAG=educated wild-nice person guess based on commonly known previous faults that occurred to other owners.
    Reasonable MM skills=being able to install a MM to read current draw while opening one circuit at a time (pulling fuses or relays) to determine which circuit is live when it shouldn't be.

    From memory, here's some items that have previously been reported to cause battery drain:
    1. Any light left on. This could be an interior light, headlight, trunk light, brake light stuck, etc.
    2. The driver door open/close switch. If this switch fails on, the courtesy lamp at the bottom of the door will remain on, even when the door is closed and the car is off. Does your door ajar light function normally? This would also usually activate a warning if the door shows open while in "drive" or "ready". Open the door and verify the light comes on, push the black button in the door jamb and make sure the light turns off.
    3. The brake power supply on the driver side of the 12v battery has been known to draw power from the battery if it has capacitors failing.
    4. There was a recent thread where a member had a washer fluid pump motor/circuit failure that was draining his battery.
     
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  6. thelonelypuppet

    thelonelypuppet Junior Member

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    Thanks for the insight so far, all.

    I am pretty meticulous about not having anything running when I leave the car--no headlights left on, nothing interior left on, etc. I had not noticed that there was a courtesy lamp at the bottom of the door, but my car never notifies me that the door is ajar.

    I believe I had read somewhere that when the auxiliary battery is not installed quite properly (I think the negative/ground isn't quite secure?) there could be a drain. I wonder if that was the case, since my husband and I DIY'ed the install of the new battery about six months ago. I do feel that we would have noticed problems sooner if that were the case, though?

    Either way, husband will be getting the battery back up to O'Reilly's later today. Will update then.

    Thanks again!
     
  7. sam spade 2

    sam spade 2 Senior Member

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    Or the onboard charging system is not working.
    The voltage needs to be checked while the vehicle is "running".

    And the connections at the OTHER end of the main cables needs to be checked too.

    It sounds like the battery is not being charged (much).
     
  8. edthefox5

    edthefox5 Senior Member

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    Since you replaced that 12 volt battery last year have you ever had to jump start this one?
     
  9. bisco

    bisco cookie crumbler

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    have them check all the connections too, especially negative to ground
     
  10. thelonelypuppet

    thelonelypuppet Junior Member

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    I have not had to jump start this one, no.
     
  11. George W

    George W Active Member

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    I'm wondering about the description of 'gel' battery. Did they possibly mean AGM?
     
  12. thelonelypuppet

    thelonelypuppet Junior Member

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    News: The battery is almost fully charged (12.15v is what they said, and they want to charge it to 12.5v) and they claimed nothing was wrong with it. They will give me a call once the battery is done charging and will test it one more time, but they're fairly certain it's fine.
     
  13. bisco

    bisco cookie crumbler

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    i would hope a battery from last sumer would charge up to at least 12.7, but that doesn't mean it's bad. ask them to a load test
     
  14. thelonelypuppet

    thelonelypuppet Junior Member

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    Final update for tonight: We reinstalled the battery after it charged up to 12.5v and O'Reilly's concluded nothing was wrong with it. I drove it around a bit and it hovered around 13.9v when fully on and driving and then 12.5v when in that idle/standby mode (not fully on). No draining.

    If this issue is not resolved now, and I experience the same problems in the future, what might be some next steps to take to try to determine the issue?
     
  15. edthefox5

    edthefox5 Senior Member

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    Do you own a digital voltmeter? There's a simple definitive load test you can do.

    Btw, the dealer is incapable of load testing a 12 volt battery based on how many posts I've seen here where the dealer says its ok and 2 days later your stuck with dead battery.
     
  16. fuzzy1

    fuzzy1 Senior Member

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    Note that the 13.9V is what the charging system is putting into the battery, and should be relatively fixed. (Gen3 has several staged levels, don't know about Gen2.)

    If the 12.5V is read very shortly after shutting down the ignition, then I'd be concerned about it being good enough. A more definitive test is to leave the car shut down numerous hours, e.g. overnight, then check again. These batteries show a relatively high voltage just after charging is removed, then gradually relax over the coming minutes then hours.

    I also don't know how accurate the Gen2 internal voltmeter is. A handheld DMM (digital multi-meter) is likely to be more accurate. My Gen3 doesn't have a voltage display, but my ScanGauge-II does, and it seems to read somewhat low.
     
  17. thelonelypuppet

    thelonelypuppet Junior Member

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    Drove this morning after letting the car sit nine hours overnight. The voltage started at 11.9v, spiked down to 11v when I turned on the headlights, then back up to 14v when the car was fully on and driving.

    Car currently at about 12.2v when parked and not fully on.
     
  18. George W

    George W Active Member

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    I hate to suggest that O'Reilly's doesn't know what they're doing, but I wonder if they are truly putting the small 12 volt motorcycle battery into the correct charging cycle.
     
  19. sam spade 2

    sam spade 2 Senior Member

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    You should not believe ANYTHING they say about electrical stuff because...................
    For an AGM battery, 12.15 is about half discharged and 12.5 is not fully charged at all.
    That takes 12.8 or 12.9 and those last few tenths are important.
     
  20. sam spade 2

    sam spade 2 Senior Member

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    This is pretty much proof positive that your battery is BAD.
    The number you see when the car is running is meaningless because that is the charging system and NOT the battery itself.
    I quit.
     
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