Energy Monitor-new owner question

<div class='quotetop'>QUOTE(Wyidelode @ Jun 10 2006, 09:12 AM) [snapback]269188[/snapback]</div>

The ICE (gas engine) in the energy display doesn't really tell you if the engine is running or not. If you have arrows from the engine it is running and providing power; if there are no arrows it may or may not be running depending on the speed the car is going and the temprature of the engine.

The green cars in the consumption graph bars are a measure of how much energy was recovered during that 5 min. peroid. Each green car represents 50 Watt hours of energy recovered. It's on page 151 in my 2005 book where the MFD is being described.

Suggestions: check this out, http://www.wikihow.com/Category:Toyota-Prius. Also try the search function on this site for newbie questions. I thought we had a forum or at least a topic for new owners but I can't find it now-maybe someone else can?

 

For even quicker reference on the green cars (which are described in the manual) just look at the top of the consumption screen and you'll see the key where it defines [greencar] = 50Wh

As a reference, 50Wh is about enough energy to power a car at freeway speeds for about 0.2 (edited becuase I screwed up the decimal earlier) miles. Amazing how many people (yes, even Prius DRIVERS) think that the battery is charged only by the slowing/braking. NOT. Most of the charging is done by the ICE unless you're coming down a very long hill.

 

i charge my battery everythin i go down that big hill, hehe, put it in b go all the way down for like 5-10 min, sometimes the battery get fully charged half way down, then theres this big noise, even if i put it back into D...

 

What you are probably seeing flipping rapidly (especially at highway speeds) is not the engine arrows flipping, but the charge/discharge arrows:

At highway speeds, the engine is almost always running, but it flips rapidly between two conditions:

1. Engine driving the wheels and simultaneously charging the battery; and
2. Engine driving the wheels with some help from the battery.

In fact, the car flips between these two conditions much faster than the display refresh rate. But the engine is not starting and stopping, only the current flow to and from the battery is flipping back and forth.

I'll disagree with Darell: Stepping on the brake produces considerable current flow to the battery for the entire deceleration time. I believe that the energy recovered during deceleration is between 1/3 and 1/2 of the energy required to accelerate the car to the same speed.

And since nobody above explicitly stated this: they are all refering to the energy recovered by regenerative braking: when you step on the brake, motor-generator 2 (MG2) becomes a generator, turning the kinetic energy of the car into electricity, thus slowing the car and recharging the battery. This is energy that a conventional car would waste by dissipating it as heat in the brake pads, and it makes a real, if small, contribution to the overall efficiency of the car in stop-and-go driving.

 

<div class='quotetop'>QUOTE(daniel @ Jun 10 2006, 06:46 PM) [snapback]269354[/snapback]</div>

Daniel -

First off, I most definitely screwed up my units and was comparing kWh to Wh incorrectly. Just came back here to fix it when I see I've been called out. I've edited that post to reflect the 0.2 miles of freeway driving that each little green icon represents. I'm saying that it will take five of those little green cars to gain you about a mile of "free" energy. I'm likely being generous as I did my quick (and initially wrong!) calculation without regard to conversion losses.... but I'll bet we're in the right ball-park now. And yes, I was WAYYY off with my 0.0002. Sorry about that. Too much cough syrup.

I am assuming that if the Prius were fully electric, it would require about 250 Wh to travel a mile at 60mph. (Four miles per kWh). It would then take five of those green cars to make up a mile's worth of energy.

Does this make sense now that I screwed my head on a little tighter?

 

I don't think of it in terms of how far one re-gen symbol will get you on the freeway, because the freeway is not where you earn those symbols. You get them in stop-and-go driving. Since the Prius is NOT an EV, the re-gen equation is not how far you can drive on one symbol; it's what percentage of your acceleration energy is recaptured during braking.

The Prius is a gas-powered car, and your steady-state driving energy has to come from gas. But because it's a hybrid, it can reduce stop-and-go losses through regeneration. That's where the little green leaf/car symbols come in, and that's how I see that re-gen energy playing into the car's operation.

For steady-state highway driving, the advantage comes in because, being a hybrid, it can make do with a smaller engine of a more efficient type, which therefore burns less gas.

Long long ago someone posted how many green leaf/car thingies it took to boost the SOC by one bar on the battery icon. That was compared to how far you could drive in EV mode on one bar. I do believe it was in the ballpark of what you posted above, except that you are talking freeway speed and this was at EV speed.

Off topic: When I consider the rumored 9-mile EV range of the 2009 Prius, and compare it with the claimed 30-mile range of the EDrive Systems conversion, I wonder if I really want the 2009, or if I'll want the conversion. It may depend on whether the 2009 increases EV speed and power.

 

<div class='quotetop'>QUOTE(daniel @ Jun 11 2006, 04:53 PM) [snapback]269708[/snapback]</div>

Yeah, yeah. I know. But energy is still energy, and it is all in the way you look at things. I constantly think in terms of how many EV miles things cost me. Watch TV for three hours - could have driven a mile. Have the freezer run for a few hours - could have driven a mile. I have a PVR that has to stay on all the time at 30W - after a year, that thing has cost me 900 EV miles! Yes, I'm that crazy.

Ah... but what if the 2009 allows REAL EV mode at speed? BIG difference compared to the 34mph limit of today's car. And what if it also allowed additional battery capacity for longer range? And plugging in! If it allows plugging in, then we're into a whole 'nuther ball game and there's no comparison.

 

Energy is energy, but the Prius is not designed to store much of it. The battery is simply there to buffer load demands, and recapture the kinetic energy of braking. A full charge may get you a mile and a half. The significant thing in the Prius is not the stored energy, but the improvement in efficiency that can be had through that buffering, and the reduced engine size and engine design improvements that are made possible by the presence of MG2 for torque for accelerating.

If the 2009 allows real EV mode up to 45 or 50 mph, that would make a difference, as would the ability to plug it in. But the EDrive Systems mod still utilizes far more electric energy, because even while driving on the highway, it is injecting electric energy, thereby reducing gas consumption.

Since I live in the suburb (a lifestyle choice: I didn't want an older house that would require lots of repairs and maintenance, and the newer houses are in the suburbs) a 9-mile EV would get me to the grocery store, but would not suffice for any other place I drive, so the EDrive Systems mod would allow me to reduce my gas usage more.

Yes, if I was a hard environmentalist I'd live in an older house closer in and use a tricycle for transportation. But I'm only a soft environmentalist: I drive the most efficient car I can and support public policies that would reduce the need for fossil-fuel use.