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Let the ICE run or shut it down?

Discussion in 'Gen 3 Prius Technical Discussion' started by HI MPG, Oct 23, 2009.

  1. HI MPG

    HI MPG Active Member

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    This is my first hybrid, so I'm trying to be as efficient as possible. On several occasions I've ended my commute home with two bars left on the battery display. As I pull into my garage and hit the P, the ICE kicks in to start recharging the battery before I can hit the Power button to turn off the car. Is this the proper thing to do (shut down immediately), or should I let the ICE complete its cycle and recharge the battery slightly before I shut it down? I know that letting the ICE run to recharge isn't very efficient, but when I shut it down immediately, the ICE stops very abruptly (like a violent jerk against the mounts).
    Is it healthy for both the engine and battery to continue in this manner? Would it be detrimental to the future reliability of the HSD components? Or should I just make sure that to end my commute with more than 2 bars?
    Sorry if this has been discussed before. I did a search and couldn't a discussion topic relating to this issue.
     
  2. Jim05

    Jim05 Occasional Quasi-Hypermiler

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    IMHO, I would let it run despite the efficiency loss. To me, the loss of gas is better than possibly harming the engine by shutting off running under load (vice idle). Just an opinion, though...
     
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  3. efusco

    efusco Moderator Emeritus
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    There's no need to let it run at all. In fact, if the trigger for this seems to be hitting the Park button, but don't bother hitting the park button. Just pull in, stop, and power down...the car automatically goes into park.

    The car will go through the battery charge balance procedure the next time you drive the car and it will do so much more efficently than it would by sitting in your garage.
     
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  4. patsparks

    patsparks An Aussie perspective

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    You are driving the last bit on EV aren't you?
    If you are then maybe drop EV for the last little bit. I doubt it is doing any harm but it is my uneducated understanding that rechargeable batteries like to be stored with a good charge in them. Switch from EV mode for the last 200 yards. Also know that driving in EV mode doesn't save any gas, after all that energy you use in EV mode comes from gas.

    (Oh my god, I am saying gas not petrol!!!)
     
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  5. Felt

    Felt Senior Member

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    HI MPG
    IMHO I suspect you are "overthinking" the situation. Just drive normally, and this amazing vehicle will do all the thinking. I rarely touch the EV button ... only maybe if I am moving from one parking spot in a lot to a safer spot (I hate door dings). I have never had to use the PWR button. My G3, IV is averaging 54 mpg w/ 5000 miles on the odeometer. BTW, I just changed the oil, and my mileage average is higher .... I do not have an explanation .... maybe the tires were underinflated before the oil change?

    Good luck.
     
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  6. dogfriend

    dogfriend Human - Animal Hybrid

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    The car is uber smart. Just drive and let it do what it needs to do. :madgrin:
     
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  7. dogfriend

    dogfriend Human - Animal Hybrid

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    It was that trip to Detroit. You were infected with a virus. Now that virus will spread and the whole continent of Australia will be calling it gas. Have you used the phrase "Ya'll" (meaning all of you) yet? :madgrin:
     
  8. spiderman

    spiderman wretched

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    Great question and one I was wondering myself lately. Normally I make it to the 3rd floor parking with two or three bars. Lately I have been required to park on the 6th. The engine kicks in just as I park. I have been shutting it down while running thinking that like previously mentioned it would be more efficient charging while moving. It would be my guess that you would want to charge the battery if you know it would be sitting for a long time or if in really cold weather.

    One thing I noticed is the brakes become really sensitive while coming down the garage floors. More so than say if the battery was full.
     
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  9. Matt Herring

    Matt Herring New Member

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    Ditto with efusco...no need to waste gas letting the ICE run at the end of your drive. In fact, pulling into your destination parking space with 3 or less bars (ideally 3) is actually pretty good driving for efficiency...meaning you maxed out the last part of your trip in EV mode without allowing the ICE to kick in (unless you ran less than 3 bars for a great distance and forced ICE to kick in prior to parking).

    It is better to run on low battery at the end of your trip than at the beginning or middle as you are not wasting ICE mid-trip to charge the battery. When I say "low battery" I don't mean the car is going to run out of battery energy...it means "lower than optimal energy" in terms of the hybrid system. If you run low battery during your drive you will notice higher than normal rpm's because some of the power normally used to propel the vehicle is diverted to charge the battery to optimal charge. You can test this by noticing how far you have to press the GO pedal to get the same acceleration while at 6 bars vs. 3 bars.

    As you get more acquanited with your vehicle you can make mental notes as to how far from your destination you can begin EV mode. When you roughly know where that point is you can begin to extend that marker by coasting in drive where possible to grab small amounts of battery charge along the way. Before you know it, you are using EV mode 1/4, 1/2, 1 mile further from your destination and you will see your mpg go up and up...good luck!
     
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  10. patsparks

    patsparks An Aussie perspective

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    No , not "y'all" but "all y'all"!

    I'll know the infection is at full strength when I start spelling zoo. "zee oh oh" insead of "zed oh oh". I hate when my son does that.

    Infection hey? Maybe that explains the sore throat and 2 weeks off work sick.
     
  11. Felt

    Felt Senior Member

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    In the deep South "Y'all" is singluar; "All Y'all" is plural.
     
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  12. Rokeby

    Rokeby Member

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    Here is a very similar thread that you may find helpful. Instead of
    focusing on using the ICE to recharge the HV battery, the discussion
    centers on using EV mode at the end of the day and a resulting low
    SOC. Same issue, different perspective:

    http://priuschat.com/forums/gen-iii...vehicle-mode-just-before-home.html#post907783
     
  13. dogfriend

    dogfriend Human - Animal Hybrid

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    Did you know that "y'all" can be used for both the singular and plural cases? I learned this in Texas when the rental shuttle bus driver greeted my boss and I with the phrase: "How y'all both doin this evening?" :madgrin:
     
  14. HI MPG

    HI MPG Active Member

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    Thank you to "y'all" who responded. I will take all your suggestions to heart. I know it makes total sense to shut down the ICE immediately, but there's that nagging feeling in the back of my head that I'm doing something wrong if I do. Like some of you have mentioned, yes, I've been riding the EV mode for the last quarter mile before reaching home for the sake of efficiency... which has been draining the battery to the 2 bars. So, I think I'll just lay off the EV so as not to drain the battery.
     
  15. patsparks

    patsparks An Aussie perspective

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    Yep, I knew that, and I know all y'all know that too.

    HI MPG, I think that is the right way to go, let the car decide what is best for economy. When you start off in the morning you might like to crawl out in EV but I only do that to keep my escape noise levels low. In the end though, the ICE has to make more power to recharge the battery and the system tries to avoid a great load on the ICE during warm-up by using a higher degree of electric assist until the engine has some heat in it. Parking with a 60% charged battery (that is where the HSD will try to maintain the level of charge) allows this to happen.

    Y'all just enjoy your cars there now.
     
  16. dogfriend

    dogfriend Human - Animal Hybrid

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    Very good. Now that you have the southern dialect down, we'll start working on the California surfer dialect next week, dude. :madgrin:
     
  17. F8L

    F8L Protecting Habitat & AG Lands

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    Or Sacramento/Bay Area ghetto slang?

    Lesson #1 Money = Feddie, grip, skrilla, cheddar, scratch, paper, cabbage, C-note, and gouda.


    As for the best meothd for parking the vehicle, I would let the car do it's thing then after you've established a good route and an average MPG for that route then try experimenting with EV mode. :)
     
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  18. jburns

    jburns Senior Senior Member

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    Wrong, wrong, wrong. The plural is "you'uns".
     
  19. efusco

    efusco Moderator Emeritus
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    Isn't that funny...did you ever wonder, with your conventional vehicle, if there was something wrong about shutting off the ICE at the end of a trip?!
    I'm gonna suggest not doing that last bit in EV then. If you're sapping the battery down that far then you're better off just driving. I don't think you're doing any great harm, but when you start up the next time you drive you have to go through S1 which puts a very heavy drain on the battery while the ICE tries to maintain a low "warm-up" RPM. You start messing with the normal cycling when the battery starts that low.

    As others suggested, you may be over-thinking this whole think. Lay off the EV button, but if the ICE tries to run as you're parking, just shut off normally.
     
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  20. rctech

    rctech Junior Member

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    I'm no expert, but my personal take on this is that:
    Even on 2 bars, the HV battery is really about 50% full (1-8 bars roughly means SOC is 40% - 80%, so about 5% per bar); Given that the HSD warranty is 8yr/100k (and I only do about 10k/yr);
    I would not worry about letting the ICE run after you parked. Just hit the power button to park/poweroff, and go have a nice dinner :)