Running the A/C with motor off

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,

 

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

 

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.

 

<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.

 

<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.

 

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.

 

<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.

 

<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.

 

<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.

Ken@Japan

 

<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.

 

<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.

 

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.

 

<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?