Running the A/C with motor off

Discussion in 'Gen 2 Prius Main Forum' started by Roger3125, Aug 20, 2006.

  1. Roger3125

    Roger3125 New Member

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    Can someone tell me the best way to run the air conditioning if you are parked or sitting for a while? Will AC run with motor off? Can it run on battery for any great length of time?

    Also I experienced the air not going on after I sat parked with air on for a while. Battery went very low but soon after driving for a while it got back into the green.

    Finally decided to try hitting the "reset" button and the air fired up fine. Wondering if this is normal or should I take it in while still in warranty?

    Thanks guys (and ladies of course)
    Roger3125
     
  2. Lil Mo

    Lil Mo New Member

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    Not sure if I can answer your question completely.

    If I want to run the air conditioning while parked, I leave the engine on. The car appears to drain the battery down until the engine kicks on.

    I have never tried it with the engine off.

    Cheers, :)
     
  3. efusco

    efusco Moderator Emeritus
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    "reset button"? I don't know what that is and certainly never would have thought of hitting it.

    But yea, just leave the car in Ready mode with the AC on, the ICE will fire up when necessary to recharge the battery.

    And just for a point of information, we Prii people make a clear distinction b/w the "Motor" and the "Engine"

    Motor = Electric motor... or more specifically the two Motor Generators (MG1 and MG2).

    Engine = ICE or internal combustion (gas) engine

    Might seem minor, but I've seen a couple threads spin pretty out of control due to someone not being clear on the nomenclature.
     
  4. pete bogumill

    pete bogumill New Member

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    hi there. the question on the a.c. just put in park and the prius will do the rest with everything left on.toyota has it all figured out real well. ;) pete
     
  5. sub3marathonman

    sub3marathonman Active Member

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    I occasionally run the A/C like that. I have to start out with six bars. I'll put the car in N, and then set the A/C at Max Cold. Then I will run it about 45 seconds and turn it off for about two minutes, and repeat that until I see the battery getting low to about three bars. If I know I'll be going within a minute I'll let it get to two bars, otherwise I'll turn the A/C off at that point.

    By doing it this way you don't run the ICE to keep the A/C going. If you put it in Park the ICE will come on sooner.
     
  6. Bill Merchant

    Bill Merchant absit invidia

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    <div class='quotetop'>QUOTE(sub3marathonman @ Aug 20 2006, 07:36 PM) [snapback]306500[/snapback]</div>
    Since the ICE is the source of all power in the Prius (as in any car), I don't know why you'd want to use this procedure. Running the HV battery low isn't good for it, and you'll only have to run the ICE more/harder/longer to make up for how you drained it.

    Just put it in Park in Ready, set the AC to Auto, set the temperature to be comfortable, and relax. This won't use any more gas and you won't strain the battery. Remember that since the AC compressor is a variable speed electric, it will only use as much energy as needed to keep you comfortable, without your hot/cold cycles.
     
  7. efusco

    efusco Moderator Emeritus
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    <div class='quotetop'>QUOTE(sub3marathonman @ Aug 20 2006, 09:36 PM) [snapback]306500[/snapback]</div>
    This is a recipe for disaster. My ICE won't come on anyway until I'm down to 1-2 bars even with the AC running, and if something happened and you forgot to check the SOC and kept he AC going with the car in N you could, potentially, drain the HV battery to a dangerously low level and damage the battery or even drain it completely. You really should not leave the car in N in Ready mode for any significant period of time.

    The engineers who designed the Prius did a fantastic job of keeping the general public from screwing things up, but one way you can 'outsmart them' is to leave the car in Ready and Neutral since that is one of the only ways to completely drain the HV battery...the other is to drive until it dies after running out of gas.
     
  8. Roger3125

    Roger3125 New Member

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    Can I assume thn from all comments that the best way to have air while parked is to leave the motor running and kick back and leave it alone. During the short time parked it will use no gas or small amount as the motor comes on to charge the battery.

    Still not claer on what an ICE is nor what I.C.E. represents. Can someone run by this one more time for us still newbies? Thanks
     
  9. marjam

    marjam Member

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    <div class='quotetop'>QUOTE(Roger3125 @ Aug 20 2006, 11:21 PM) [snapback]306524[/snapback]</div>
    The ICE is the Internal Combustion Engine. (Gas Engine). The motor is one of the two electric motors. Yes, you can assume the best way is to stay in Ready mode, shift to Park, set the A/C to where you are comfortable, and enjoy the car.
     
  10. McShemp

    McShemp New Member

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    If you had a car before, and sat parked with the a/c on, then just do what you did before.

    If this is your 1st car, park and sit ... don't turn the car off until you're ready to get out.
     
  11. sub3marathonman

    sub3marathonman Active Member

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    <div class='quotetop'>QUOTE(efusco @ Aug 20 2006, 11:09 PM) [snapback]306517[/snapback]</div>
    I would have to disagree. And maybe I didn't explain completely the procedure I use.

    First, it is not "a recipe for disaster." It is my understanding that the car would shut off, even in N, if the battery became discharged down to its lower acceptable limit according to Toyota. And its lower limit, with no bars, is not "completely drained," it is down to about 40% charge according to the chart that efusco provided. Yes, it possibly would in some small way negatively impact battery life, but no more than anything else the Prius does normally. It is possible to drive the car normally down to two pink bars. It is possible to sit in the car at a light with the A/C running and get down to two pink bars. (Maybe even down to one pink bar, I don't know because I turn the A/C off at that point.) Unless I keel over from a heat stroke or a heart attack, I'm not letting it get any lower than two bars. This is much different from overriding the safety mechanisms and driving the car when it is out of gas.

    I am sitting in the car, I am watching the display. I don't have anything else to do because I'm waiting for the people to come back. If I run the A/C continuously in Park, the engine will come on much sooner. So by using the A/C intermittently I don't use as much energy from the battery. Or put another way, I'm able to keep the car at a cool enough temperature for a longer time period. Yes, it is true that no matter what, I'll be burning gasoline in order to replenish the batter. I just want to wait until I'm actually driving for that to happen. And yes, there is a slightly wider temperature range than just running the A/C at the previously set temperature. I'm willing to endure that in order to save a bit of the battery energy.
     
  12. efusco

    efusco Moderator Emeritus
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    <div class='quotetop'>QUOTE(sub3marathonman @ Aug 21 2006, 09:43 AM) [snapback]306684[/snapback]</div>
    1)The car will NOT shut itself off if you are in READY and Neutral...it will drain the battery down to nearly 0 charge.

    2)Yes, if you are diligent and watch the Energy screen and don't let it get below 3 bars, etc, as you described, you'll be OK. But let's just say your spouse/SO was watching as you routinely put the car in N with the AC running but didn't appreicate the attention you were giving to the display, or that someone else read this thread and didn't appreciate the importance of the SOC when in Neutral, or that maybe you didn't pay as close of attention as you usually due b/c you were distracted by an interesting news story on the radio or by the book or magazine you were reading and the SOC got seriously too low. Unlikely, sure, impossible, definately not.

    3)No matter the degree of diligence you're giving this, you cannot do a better job of protecting the battery than the car is already programmed to do. If you drop into drive with 3 bars and run the ICE then you may be worsening your FE and unnecessarily prematurely charging. If you shut the car off then you force another warm-up cycle which also tends to significantly discharge the battery briefly. If you do let the SOC run below the 40% mark then you're shortening your battery life by some finite amount.

    The bottom line is that there is the potential to have untoward effects on your car with your technique. By leaving the car in Ready mode that potential is completely eliminated and you are letting the car work as it was designed and intended.


    One additional point, if you're willing to tolerate the swings in temp, then I suggest you just set the AC at 82 or 83 degrees. I find that a little too warm to feel 'cool', but it certainly isn't 'hot'. The battery drain at that temp is very low (except in the most extreme heat). At a stop I usually see around 3.5 amps drain compared to around 1.6 amps with just the fan (no AC) and around 6-8 amps with the AC set at 78 degrees. You'll get nearly double the time before the ICE starts up to charge.
     
  13. sub3marathonman

    sub3marathonman Active Member

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    <div class='quotetop'>QUOTE(efusco @ Aug 21 2006, 10:56 AM) [snapback]306692[/snapback]</div>
    If that is true, and I have no reason to doubt efusco, then it is actually a potential "recipie for disaster." I would have thought that Toyota would have done a better job to protect the battery. Also, it is true that others might not pay as much attention to the energy screen as I do.
     
  14. efusco

    efusco Moderator Emeritus
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    Yup, that's why I pointed this out. If you put the car in Neutral...or heck, even leave it in Drive, and open the driver's side door you get a warning message on the MFD that tells you the battery cannot charge in Neutral.

    To be honest, there does seem to be a point that the car will shut itself down with some residual charge. A few folks who've run out of gas and then driven further than they should have on battery alone have had the car shut down. They were then able to restart once or twice and move very short distances before it shut-down again. To my knowledge each of those people was able to add gas and get the car running even with the very low battery charge. I have no idea exactly how low the charge was allowed to go in those conditions, and I hope I never personally figure it out! In any case, it isn't a good thing for that to happen.
     
  15. ken1784

    ken1784 SuperMID designer

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    <div class='quotetop'>QUOTE(sub3marathonman @ Aug 21 2006, 11:43 PM) [snapback]306684[/snapback]</div>
    I would have to disagree. And maybe I didn't explain completely the procedure I use.

    First, it is not "a recipe for disaster." It is my understanding that the car would shut off, even in N, if the battery became discharged down to its lower acceptable limit according to Toyota. And its lower limit, with no bars, is not "completely drained," it is down to about 40% charge according to the chart that efusco provided.[/b][/quote]
    One of Japanese folks did this stupid test. :)
    Yes, the test was stupid, but the results is invaluable.
    In Ready, Neutral and AC on, he saw the battery level was going low, of course.
    A warning was displayed on screen saying "HV battery voltage is low. Stop your vehicle immediately and call Toyota service station!".
    The AC compressor was stopped and only fan was blowing hot air.
    The SOC was just 18.5% according to CAN and the level stayed there.
    Then, the voltage of the aux battery became down, which meant the DC-DC converter was not working any more.

    He finished the experiment there. :)

    [email protected]
     
  16. CrazyRussian

    CrazyRussian Junior Member

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    <div class='quotetop'>QUOTE(sub3marathonman @ Aug 21 2006, 07:43 AM) [snapback]306684[/snapback]</div>
    Why some people would complicate a simple process, a simple straight line into a multi dementional labyrinth, is beyond my comprehention.
     
  17. efusco

    efusco Moderator Emeritus
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    <div class='quotetop'>QUOTE(ken1784 @ Aug 21 2006, 10:53 AM) [snapback]306723[/snapback]</div>
    Thanks Ken, it's good to be reminded, once in a while, that there are people in the world that'll do things that are even more stupid than the things I do....

    It is interesting, though...I wonder if there's simply a nominal voltage requirement for the DC-DC converter to work and that that minimum is so low that the 12v would die, thus killing the car, before the HV battery could possibly die. It would still be a sucky PITA because to start the car you'd first have to charge up the 12v again, then you'd have to start the car and hope that there was enough charge in the HV battery to allow MG1 to crank over the ICE so that the ICE could recharge the HV battery.
     
  18. sub3marathonman

    sub3marathonman Active Member

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    <div class='quotetop'>QUOTE(CrazyRussian @ Aug 21 2006, 12:46 PM) [snapback]306742[/snapback]</div>
    That CrazyRussian doesn't comprehend isn't a big surprise, but the reason is really simple. It is an attempt to keep the car comfortable for as long as possible with the minimum use of energy. This is what Roger3125 originally asked, and what I tried to help with. Now, if that is what actually occurs from the procedure I use as opposed to just putting it in Park and letting the ICE run when it wants is apparently a matter of debate. But, at least in this situation, I am willing to match wits with the computer to keep the fuel used to a minimum.

    It is my understanding too, that even in Park, the ICE is charging the battery, and the battery is supplying the A/C, so there really is no energy difference in either method. It seems that it should be possilbe to determine if running the A/C at Max Cold for 27% of the time uses less energy than leaving the A/C set to a specific temperature, and at what temperature that crossover occurs. But I don't have the scanning tools to do that. I will leave that to the experts.
     
  19. DanMan32

    DanMan32 Senior Member

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    You can turn off the AC compressor from the display. The fans will still go, so you'll get some residual cooling.

    If you want to experiment, you can compare the duty cycle of when the ICE runs to when it doesn't run using both cooling methods once you reach the low SOC threshold.

    There's really no benefit to running the car in N. In READY, the HV battery is still being drained, but is prohibited from being charged. Yet if you leave it in Park, the ICE can be started as needed to maintain the HV battery charge. You can do what you like with the HVAC. Even with the AC off though, there is still some drain on the HV battery, as the DC-DC converter maintains the 12V to all the ECUs and other operating components.
     
  20. bhaynnes

    bhaynnes Member

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    <div class='quotetop'>QUOTE(sub3marathonman @ Aug 21 2006, 11:33 AM) [snapback]306835[/snapback]</div>

    I just put the car in park and leave the air on. No worries, when the battry gets too low, it ICE comes on and charges it up. Why in the hell would you want to complicate it?
     
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