Conserving power in standstill traffic

Discussion in 'Gen 3 Prius Main Forum' started by Pijoto, Jun 1, 2016.

  1. Pijoto

    Pijoto Active Member

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    So, I got stuck in standstill traffic for about an hour due to bad weather and wreck up ahead, and barely inching along the highway, I was surprised how fast the battery was dropping and having to turn on the engine to recharge it, killing the MPG; normal drive home I get around 50 MPG, it dropped to 38 due to all the idling. In such situations, do you guys just place the Prius in "Park" in order to shut down the electric motor (I'm assuming that's what park does) so it doesn't idle to conserve power? Would probably be an annoying way to drive regularly, but if you know you're gonna get stuck for awhile, I may try it next time...
     
  2. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Barely inching is the worst, eats up the charge then starts in on the gas.

    If traffic's completely stopped at least you can shut down.
     
  3. mmmodem

    mmmodem Senior Taste Tester

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    Why don't you just shut off the car?

    Park won't do anything different besides giving your foot a rest. If you need heat or AC then use the ECO button to minimize HVAC usage. That should decrease battery usage.

    I usually roll the windows down and shut off the car waiting for train crossing.
     
  4. Pijoto

    Pijoto Active Member

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    Don't want to completely shut off the car...want to be able inch along when ready, rather than taking too much time to start up again...not to mention running the air and radio. I always thought the Park button stops the EV motor from moving, and that may be a better way to conserve power during these gridlocks...
     
  5. devprius

    devprius /dev/geek

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    Did you have climate control system on by any chance? I.e blasting the A/C, or the heater on to keep you warm? If you had the heater on, that forces the engine to run to provide heat. If you had the A/C on, then it uses the traction battery to run the A/C compressor/fans. When the battery gets low enough, gas engine fires up to recharge it...
     
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  6. Pijoto

    Pijoto Active Member

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    Just had the fan on, turned low, shouldn't use that much energy, and rather not have the window down on the freeway and breath in all the exhaust directly...
     
  7. mmmodem

    mmmodem Senior Taste Tester

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    Then there really is nothing else you can do to conserve energy.
     
  8. Starship_Enterprius

    Starship_Enterprius Active Member

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    There's just no way around it. Stop n go traffic is a real mileage killer.

    The only thing I find that somehow slightly helps is when creeping in EV not to push the energy bar up to the middle to try to accelerate faster, because it barely makes a difference anyway. The electric motor is just not that strong.

    Initially at the start you may need to just to break from standstill. But as soon as you start moving and you've given your car a reasonable push, keep that bar as near to the left as possible because it will still accelerate with only the slightest difference than if you used all the EV bar area. Or you can neutral glide also to the next stop.

    Also (if not already), use the Eco mode when using AC.
     
  9. Pijoto

    Pijoto Active Member

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    Ah, didn't think about placing it in Neutral to kill the electric motor...I've only ever placed it in Neutral once :p The EV motor doesn't seem that strong, but it still takes quite a bit of juice to move a 3000 pound vehicle...so even on idle, it must use a ton of energy. And, Yeah, I always drive in Eco mode, try to use the fan as much as possible to avoid turning on the A/C.
     
  10. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Could change your work hours, or find another route? Just a thought.
     
  11. xpcman

    xpcman Senior Member

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    If your stopped with your foot on the brake then it doesn't matter what the transmission setting your using, No energy is being used to move the car. Once you take your foot off the gas then you use battery energy for the built in creep. The car will only move about 1/4 of a mile total before the battery needs to recharge.
     
  12. Starship_Enterprius

    Starship_Enterprius Active Member

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    neutral is only good for saving gas when gliding with the ICE off. But if the ICE is running, it is pretty useless because the ICE won't recharge the battery so you lose more. When stopped, putting it in Park like you did is better.

    As for saving on AC, put it at automatic climate control in Eco mode and the highest you can bare that still blows a little cold air on your skin. You don't really need it at a specific temp to feel comfortable. All you need is the sensation of chilled dehumidified air intermittently blowing on your skin, at say around 2 3 bars fan speed (automatically set by the climate control).

    If it blows harder than that, your AC is working too hard. When it gets too hot for you, click down one lower on the temp buttons. I usually start at around 28C(82F) at the start and seldom clicked down to 26C(78F) by the time I get home 45 minutes later. And we've been hitting 90F degrees here last week.
     
  13. Pijoto

    Pijoto Active Member

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    This was just an isolated incident, some storms earlier and an accident caused a major backup on the drive home.

    I assume the car always uses some power to "creep" when in Drive mode, so that you can idle along like a regular car...not sure if energy is cut off completely when you're stopped with your foot on the brake.

    No neutral then :p I have slept in my car overnight with the car on in Park, in order to run the fan, it barely used any power all night, so I assumed the Park mode shuts off the electric motor....so hopefully this would work next time I'm stuck in standstill traffic again.

    Right now it's cool enough to get by with the fan, but when it gets too hot, I run the A/C like you said, blowing directly on my face with 2 to 3 bars.
     
  14. CR94

    CR94 Senior Member

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    While you were only intermittently "inching" in Texas in June in the daytime, with air conditioning, you may have been spending more power on air conditioning than on forward motion. The only solution to that is to keep the temperature setting as high as you can bear, or turn AC off. The fan alone at lower settings consumes relatively little.
    Yes, energy to the drive motor is cut off when you're stopped with your foot on the brake, so that condition uses very little more power than being stopped in PARK (the difference being the brake lights). When you take your foot off the brake in "D", some power goes to the motor to provide "creep."
    Neutral won't help much, and could cause a problem, because in neutral the engine can't restart to recharge the battery when needed. (It might help slightly if you're intermittently inching downhill, and are careful not to overuse it.)
     
  15. Tideland Prius

    Tideland Prius Moderator of the North
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    Well usually the first things I do if I hit traffic where I know I'll be crawling for a while is shut off the A/C and go into ECO mode.

    In the Gen 2, the battery lasts 8 mins with the A/C on. With the A/C off (but the fan still running), the battery lasts at least 30 mins until 2 bars so you have that going for you. In the Gen 3, I think I've lasted about 30 mins as well with the A/C off. Turning the fan off completely may only buy you an extra few mins so I don't think it matters that much.

    If you go into neutral, be aware that neutral doesn't charge the battery so if the engine is running, make sure you're in D or P so that the engine will charge the battery (while waste the idle).

    D with the brake fully depress and P should be the same thing, no? Doesn't the computer cut power either way? The only way P would save power is if your right leg isn't as strong or if you have a tendency to rest lightly on the brake pedal. If that's the case, then P will save power because if you're depressing the pedal lightly, even though the car is stopped, the computer will still draw power from the battery to the electric motor. So essentially you're wasting the battery power. You have to use the Energy Monitor to see if that's happening. But you if know you depress the brake pedal hard and you can maintain that pressure, you'll be fine.

    TL;DR The NiMH battery has a charge of about 30 mins from 6-7 bars to 2 bars so anything longer and you will be idling to recharge.
     
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  16. Pijoto

    Pijoto Active Member

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    I'll have to test if energy is still being drawn to the electric motor when your foot is fully pressed on the brake, vs Park...and again, I didn't have A/C on, just the fan on low, yet the battery was depleted when I was stuck on a virtual standstill only moving a few hundred feet in under half an hour... Or like you said, it'll deplete in about half an hour anyway to recharge...next time I get stuck in traffic like that again, I'll check.
     
  17. Tideland Prius

    Tideland Prius Moderator of the North
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    Yeah if you know you're not going to move, I'd turn the car off. You can see if the traffic starts moving by looking up ahead.
     
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  18. bisco

    bisco cookie crumbler

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    this is where a fully loaded pip comes into play.
     
  19. CR94

    CR94 Senior Member

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    Whether or not the engine starts to recharge the battery while you're stopped makes little difference in the end. Either way, sooner or later the lost energy will have to be replaced.
     
  20. socal13

    socal13 livin in the foothills...

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    they put a/c in the cars for the purpose of keeping you cool... so burn a little gas... who cares! You're still going to get great mileage.
     
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