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Battery loses charge overnight

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by THoover392, Aug 11, 2006.

  1. THoover392

    THoover392 New Member

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    I've searched and havent seen this one yet...

    When I turn off the Prius at the end of the day, It usually shows a high battery charge. (the last few miles of my commute home are slightly downhill) But when I start it up in the morning sometimes it's down to two or three bars left. This doesn't make sense to me as it's colder in the morning and I havent left it running all night. This happens all the time. (I think I will start keeping a log of it)

    Anybody else ever notice this or have an explanation for it?

    thanks in advance

    OG
     
    #1 THoover392, Aug 11, 2006
  2. Lil Mo

    Lil Mo New Member

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    I have not seen that with my Prius. The SKS system will use energy and will drain the battery over a long period of time (weeks?), but in the course of eight hours, I have only seen small changes in the "as left" level and "as found" level. Changes in temperature may play a role.

    Let's see if anyone else has seen this...

    Cheers, LM
     
    #2 Lil Mo, Aug 11, 2006
  3. Tideland Prius

    Tideland Prius Moderator of the North
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    That can't be right. Even the lights or SKS will only affect the 12V battery, NOT the HV battery.

    Sometimes it'll change by one bar if it's at the borderline when you shut off (same for fuel gauge) but not by two or three bars. Have it checked.
     
    #3 Tideland Prius, Aug 11, 2006
  4. Jack Straw

    Jack Straw New Member

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    zzz
     
    #4 Jack Straw, Aug 11, 2006
  5. benighted

    benighted New Member

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    NiMH batteries will self-discharge on their own. But I don't know if there would be a significant change overnight even though I've noticed what the OP describes on mine. Maybe it has something to do with the temperature?
     
    #5 benighted, Aug 11, 2006
  6. ThetaSigma99

    ThetaSigma99 Junior Member

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    I have seen this with my 2005 Prius BC. It seems to happen to me in very hot weather. When I park at the end of the day, I have a fairly high battery charge. The next morning, when I start it up again, I'm often down to 2 or 3 pink bars. At first I thought it had something to do with whether the A/C was turned off before I turned off the car, but it seems as if this has nothing to do with it.
     
    #6 ThetaSigma99, Aug 12, 2006
  7. nwprius

    nwprius Member

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    I frequently go for a week or more withouot moving my car and see no loss in the battery bars. My car is in a garage that does not have much of a temperature change. Perhaps if the car is parked when very warm and then started in a much cooler period it would show some change, though I doubt that would cause the change either. Please do document the actual change along with a certainty as to the conditions in which the car is left, with certainty that all items are turned off.
     
    #7 nwprius, Aug 12, 2006
  8. THoover392

    THoover392 New Member

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    Thanks for all the quick feedback....

    It's good to hear Im not the only one who has seen this. There is definately a change in temperature between shut down at the end of the day and start up in the morning. I live in the Arizona high desert and its hot in the afternoon and cold in the morning. No garage unfortunately.

    I checked it this morning and it was only one bar lower so that wasn't a big deal when I started it. However within 2 minutes of driving, my battery went from three bars down to only two or three bars left. I guess that could be normal.

    I've decided to keep a log so I'm not guessing on this stuff...

    I'll post when I have some data...

    OG
     
    #8 THoover392, Aug 12, 2006
  9. tmgrl3

    tmgrl3 Member

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    So far my 06 has pretty good batter memory...and is about where it was when I shut it off....

    terri

    Yesterday, after servicing, it was in the pink...I felt they forgot to turn the car off...I called about it today. Got an apology but said it was unlikely since it was only in the bay about a half hour, so even if it were on, it wouldn't drop that low...I've had mine on for that and longer and it didn't drop that low.

    I agree with the others...I would get it checked, since there is supposed to be "battery memory."
     
    #9 tmgrl3, Aug 15, 2006
  10. efusco

    efusco Moderator Emeritus
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    The battery SOC display is not an exact representation of the exact SOC. There is some significant delay in updating of the SOC as well as significant hysteresis in the range.

    Given that, and the possible changes that occur with temperture changes and the fact that the battery ECU resets and takes new readings at start up AND the fact that although the 12v does not directly drain the HV battery when the car is off, there is an almost immediate draw from the HV to the 12v upon start up to recharge any drain that might have occured during the night.

    So, a swing of 1-2 bars from the shut down SOC to the first SOC in the morning I'd consider normal. IF, however, there are large swings in the SOC during normal operation or the SOC is dropping to 1 pink bar when shut down with higher SOC (5-6 blue bars) then I'd consider that an abnormal behavior.
     
    #10 efusco, Aug 15, 2006
  11. keydiver

    keydiver New Member

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    I've noticed this same issue since the hotter weather arrived. Its very irritating to park the car at night with 6 bars, and only have 3 or 4 sometimes when I start off the next morning. It would be interesting to park the Prius in the garage overnight instead, to see if the issue is less pronounced, because it definitely seems heat-related. By 9 AM when I leave for work it is already cooking pretty hot here in South Florida.
    As Efusco said though, some of this could be because I'm usually in Stealth mode for the last minute before I park for the night, as I travel through my development, and the drain may not show up immediately on the gauge. Then, I know it takes some more power to start the engine first thing in the morning, so the power loss overnight might not be as bad as it looks. Without a Scangauge or something to actually monitor the battery I've tried to not let it bother me.
     
    #11 keydiver, Aug 15, 2006
  12. RunnerCNY

    RunnerCNY Junior Member

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    Re: Battery looses charge overnight

    Sporadically, the traction battery on my 2005 with 165,000 miles will drop down to two bars overnight after being almost fully charged (green zone). This isn't consistent. I'm wondering if something isn't turning off when I turn off the car at night. Is there a way to test the battery pack? I saw something about a TSB on the hybrid B + rail. Any help or suggestions would be greatly appreciated.
     
    #12 RunnerCNY, May 22, 2012
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