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Battery drains while parked under the hot sun

Discussion in 'Gen 3 Prius Main Forum' started by Heat Gun, May 17, 2014.

  1. Heat Gun

    Heat Gun Junior Member

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    UPDATE: 6/11/2014 (Updates are in red)

    Hi all,

    I have purchased brand new prius 2014 with solar panel about 6 weeks ago, I've driven 2100 miles already and I have few concerns,
    Now almost 3000 miles

    1- Battery drains while parked under the hot sun (solar fan is turned on, I didnt try without turning the fan off), Lets say battery level is 60% by the time I park and few hours later I find battery level at 20%. I dont have this issue if car is parked at home (covered parking)
    Believe or not, it doesn't happen anymore, well happened once when I left at valet parking but I guess valet guy left car on, other than this never happened, my guess is car was too new and was adjusting or something.

    2- I haven't seen the battery fully charged yet,
    I live in West Los Angeles where you have crazy traffic, weather usually not too hot, about 70F for entire year, (except past two weeks over 100F) once I saw battery level at 80% but that's all, it is usually about 50%
    I am sure this all about my driving techniques, now it is 80% full all the time.

    3- I get about 40 MPG and I believe I am a calm driver, It is maybe I am doing something wrong or car got some issues.,
    Last tank was 47 MPG (49 comp), and now screen shows 53 mpg with 150 miles since last fuel up

    Thank you guys for trying to help out
     
    #1 Heat Gun, May 17, 2014
    Last edited: Jun 24, 2014
  2. JC91006

    JC91006 Senior Member

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    It's too soon to tell if anything is wrong with your car. It's still in the break in period. The battery does not normally show a full charge unless you have extended periods of downhill driving. Next time you decide to drive to Las Vegas, you'll have an opportunity to see it fully charged on the downhill drives.

    Your car is warrantied for 3 years/36000 miles. I say give it more time, get used to it a bit and then see if you still notice something different.
     
  3. KennyGS

    KennyGS Senior Member

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    Seems like you should be able to show better mpg than 40. Keep driving, and you should see it improve.
     
  4. fuzzy1

    fuzzy1 Senior Member

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    Is the ignition really Off?
    Not an issue. Flatlanders may never see it. The car's aimpoint is 6 bars (75%), which is also close to the best for battery longevity. It will go higher with braking regeneration, and you will need a reasonably steep descent to get it full. I sometimes fill it with a 400 foot descent in 2 miles, but not always. The several thousand foot descents on 5% grades always fill it.
    Newbies should drive 'normally' for a few tanks to get a baseline MPG before trying for better results. But by 2100 miles, you should already have that.

    Next: Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new
     
  5. David Beale

    David Beale Senior Member

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    Further, do keep in mind the battery charge indicator is a guess at best. The value shown will change with battery temperature. In short, it's just a "bells and whistles" thing. It doesn't really tell you anything useful. In fact, it lies all the time. For example, 100% is actually around 80% and 0% is actually around 30%. The HSD controls the battery charge level. You can -influence- it but you can't control it.

    As mentioned above, do be careful that you actually turn the car off when you leave it. You can tell if you did because it will give you an audible warning (close any door with no fob in the car and the car in "Ready" and it will ding a couple of times).

    So relax and watch the blinking lights. ;)
     
  6. Heat Gun

    Heat Gun Junior Member

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    Ignition is off for sure,
    My wife left the car on first week when we purchased, key inside, car was running, lights were on, two hours later car was still there and running :).
    I always press power button to turn off, then check mpg on display, take the key with me, lock and and make sure car doesnt beep behind me.

    Car still has original tires and rims, 36psi front 35 rear.
     
  7. WE0H

    WE0H Senior Member

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    Bump those tires up a bit over 40 psi. That will help mpg's. Mine are upper 40's when I get to drive my car.

    I'd like to say I also have noticed my HV battery level dropping from using the solar vent but I would have to check it out again this season to verify. It's been many many months since I even sat in my car ;)

    Mike
     
  8. David Beale

    David Beale Senior Member

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    Well, if either of you are implying that somehow the battery is being drained by the fan please explain how that would be possible, given that the relay in the traction battery pack is -open-, and it opens -both- the positive and negative leads. There is no connection between the traction battery and the car. Zero, none.

    I can think of only three possibilities as causes to this -indicated- battery charge level drop, in order of probability -
    1. The battery temperature has changed enough that the system -thinks- the charge level has changed (temperature change causes battery voltage to change).
    2.You left the car in "Ready".
    3.Somehow the change in temperature has caused expansion of the battery pack and that has caused an electrical leak inside. I have never heard of this happening, but it's -possible- (barely). Given that in use the pack temperature gets much higher than any ambient temperature we are, hopefully, likely to ever see!

    You might want to check the battery vent inlet to make sure it's clear. If it's blocked the battery will operate hot, and that will increase the operating vs non-used temperature difference. And that will increase the difference the system will think there is in charge level.
     
    hybridbear likes this.
  9. WolfpackBill

    WolfpackBill Senior Member

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    I've noticed that drop in battery level as well. I parked outside in 80 degree bright sun for almost 9 hours and I usually come back to my car with the fan running and when I start the car, the battery level is down to 2 or 3 bars. I know for sure that when I get out of the car in the morning my battery level is a shade under the full mark.
     
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  10. WE0H

    WE0H Senior Member

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    This is starting to sound way more familiar to me now that I think of it. I know for a fact there is zero wrong with my car. It has fifteen hundred (1500) miles on it. It is brand new yet. Not a chance the interior vent would be covered with anything as nobody or nothing ever gets put back there [​IMG]
    As far as leaving it in ready, impossible for me to do that. I fully understand how the car operates other than some of the particulars like how the software & hardware are running this solar vent roof or getting Entune to operate correct every time I hop in the car :) but that boot up/power up button, piece-o-cake [​IMG]
    I will run some tests when I get to take it out this season. It's still in storage.

    Mike [​IMG]
     
  11. retired4999

    retired4999 Prius driver since 2005

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    It is time!!!!!;) :whistle:
     
  12. DrPepperholik

    DrPepperholik Active Member

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    Mine doesn't do this. I drive my car daily and it's around 1,400 miles now. I haven't noticed the battery being lower when I leave work than when I got here. I'll pay closer attention to this though and see what I can determine. Tomorrow is supposed to be 92 so I'll check it out.
     
  13. Heat Gun

    Heat Gun Junior Member

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    Well, mine does for sure! :)
    Does your prius have solar roof? I dont know if it has anything to do with it tho.
    Today I parked my car under 85F for four hours, battery was a level below full then I found battery had only two bars when I returned back to my car, I mean I understand 1-2 drops but hey from full to almost zero.

    By the way, finally I had a chance to bump tires up to 40/38 and so far my MPG goes around 48~ with 100 miles on it since last fuel up
     
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  14. bisco

    bisco cookie crumbler

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    why should it drop at all? maybe one bar because it was just over the edge, but i can't see more than that unless the heat has something to do with it. but i parked my '04 and '08 in full sun in 90 degree weather for 8-10 hours for years and never experienced that.
     
  15. WE0H

    WE0H Senior Member

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    I have a feeling there is more electricity being used than the solar panel puts out.

    Mike
     
  16. fuzzy1

    fuzzy1 Senior Member

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    But where is it coming from? The traction battery is supposed to be disconnected by a relay when the ignition is off.
     
  17. Heat Gun

    Heat Gun Junior Member

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    I'll have it check tomorrow or Wednesday from dealer where I bought it, I'll update this as I have more info
    Here is another photo of my car :)

    20140524_121409.jpg
     
  18. macman408

    macman408 Electron Guidance Counselor

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    According to this, heat will lower the voltage of a battery. We already know that the Prius uses coulomb counting while operating to track the battery voltage, augmented by adjustments (probably mostly based off of voltage) that happen when you turn the car on, which corrects any error that may have accumulated during the coulomb counting.

    So you park the car, the battery gets nice and toasty, and the voltage drops as a result. When you turn the car back on, it sees that the voltage is lower, so it shows the battery SoC as lower, although the total stored energy is probably still the same.

    So here's your next experiment - if you find that you can reproduce it reliably, try parking in a location where it happens, but leave the car until nighttime, or something like that. Or, possibly, turn it on (for a few seconds) when it's hot to check the battery level, then again at nighttime when it has had a chance to cool off for a few hours. In either case, maybe you will find that when the battery has had a chance to cool off again, the SoC displayed has recovered to what it was when you first parked the car.
     
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  19. WE0H

    WE0H Senior Member

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    Good question. Seems there are always new things learned about these cars. Really wish a Toyota engineer could tell us here what is going on. Maybe someone here will dig into it and figure out what the car is really doing when that solar fan is activated. Seems like there is more than just the solar panel and that switch on the dash to the solar vent system.

    Mike
     
  20. David Beale

    David Beale Senior Member

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    The only problem with -thinking- because it's parked in the hot sun the battery temp. is higher is that the battery -operates- at a high temp. Probably higher than afternoon ambient. And because the battery is tucked away -out- of the sun and -out- of the interior air (it's under the floor), it will probably be closer to ambient temp than interior cabin temp.

    You need to -measure- the battery temp to really know what it is and to even have a chance to figure out what is happening. You can probably get the battery internal temp from a Scangauge or other system scanner.

    Oh, and as posted by others and me, the battery is -completely- disconnected from the car by the relay. The battery computer is still connected, but the battery is not.