Energy monitor

[dslomer]

So far, I LOVE my new '06 Prius. Over 50 mpg for 300+ miles. Accelerates as needed as well as anybody could ask for. So there are no problems with performance. But ...

I don't plan on watching the energy and consumption monitors as much as I have, but I can't help noticing how often the arrow flow to and from the electric motor and battery changes--it's like seeing railroad crossing lights out of the corner of my eye. It's probably the way it's supposed to be--at least Toyota service says so. Anyway...a few questions.

(1) When the blue battery charge indicator bars are below halfway, recharging occurs immediately as it should. But never more than 6 of the 8 bars are blue. If it's never going to get to 8 out of 8 bars, why have 8? [Reminds me of Spinal Tap's speaker volume control going up to 11.] I ask this because my next few questions might be related to this.

(2) On the x-way, the yellow arrows usually show the electric motor cycling on and off, giving more power to the engine like 20 times [or more?] per minute, but it's off longer than on. It's almost like the arrows are flickering on and off. If that's really what's happening to the motor, isn't that bad?

(3) In town, the arrows from electric motor to battery sometimes cycle on and off about 20 times per minute. If I'm below 8 out of 8 blue bars, shouldn't it be continually charged? [If I understand, it takes either braking or gasoline to charge the battery, so maybe that's why the cycling off before 8 bars, for fuel efficiency, but the frequent motor short-cycling still makes me wonder.]

(4) When I'm coasting, not braking, sometimes the blue arrows show the battery is getting charged, but often NOTHING's happening--no flow arrows anywhere. Shouldn't the battery be getting charged the whole time if all the bars aren't filled? It's like I'm in "N", where the manual says no charge will occur, but I'm not in N.

(5) Today when I got out of the car, the bars were above halfway. When I got back in, they were below half. Why should that happen? I guess it was marginally above, then I started and backed up, which made it marginally below. Agree?

Of course, if the monitor isn't really a true picture of what's going on under the hood and other places, there's no need to ever look at it. But isn't it supposed to be monitoring, in real time, what's actually going on? A Toyota service guy says all the above flashing and bar action is OK and that, yes, that IS what's actually going on "because the computer says to" for optimum performance.

It's not that I don't want to believe the guy; I just want other opinions and advice.

And I'm not eager to cut short the life of my electric motor or battery from day one!

Thanks for any advice.

Dave

[MattInMD]

1) The prius *intentionally* does not charge the battery completely from the gas engine. If it did, it would have no room left to store energy in when you hit the brakes, and that energy would be wasted. You will, on rare occasions, see more than 6 bars. When this happens they change color from blue to green. I've seen it happen twice, but I've never seen it hit all 8, only 7.

2) AFAIK, this is perfectly normal, as mine does it too. To the best of my understanding, what's really happening is some of the excess gas-engine torque is being absorbed by MG1, and shunted over to MG2 in bursts. See Omnipelagos.com ~ article "Hybrid Synergy Drive" or some other similar site on how HSD works.

Also, I do not see how cycling on and off could possibly cause the electric motor any harm. The motors are brushless, so it's not like there's any extra wear at start-up time. Heck, with electric motors it is typical to cycle them on-and-off thousands of times per second in order to control speed. (this is called "pulse width modulation", and is also how a household light dimmer works. Cycling between full-on and full-off very rapidly, and just changing the percentage of "on" time vs "off" time.)


3) see the answers to 1 and 2. Yes it does it for fuel efficiency as stated in 1. And I don't see how it can cause excess wear, as per 2.

4) No, there should not always be arrows somewhere. This is called "gliding", and is done by keeping your foot very lightly on the gas. At this stage, no gas is consumed, no electricity is generated or used. The car is just rolling. It will loose speed, but fairly slowly.

If you let off the gas all the way, the computer will automatically simulate the "engine drag" of a normal car by lightly engaging the regenerative brakes. At this point the blue arrows come on. However, the car slows down more rapidly.

Generally speaking, gliding is a good thing, as you'll get the most MPG over long distances by gliding most of the time and accelerating as needed to regain lost speed.


5) probably. MG1 also acts as a starter for the gas engine, and draws the power it needs to start it from the hybrid pack.

Well, the arrows are a completely accurate representation of the flow of power under the hood. However they have simplified a few things, mostly to keep the display from being even busier than it already is.

- They only show one electric motor, not two. However, this explains how sometimes power will be both going into, and coming out of the electric motor. It's really going into one, and out of the other.

- They don't show you if the gas engine is running or not. They only show if power from it is being transfered somewhere. There are some situations where the engine runs, but is effectively in neutral and is consuming gas without any arrows.

[dslomer]

MATT!! I REALLY appreciate the time you took to write your reply!

It's exactly what I was looking for--a well-written, clearly-knowledgeable answer and description of what's going on. And I sure didn't know there were TWO electric motors.

Hey, just curious about another thing:

Assume that I fill the tank to some point, say "X", which is a few inches below the top of the filler tube. I then drive 456.1 miles and refill the tank to the same point X, thereby knowing precisely how much gas I used--let's say 9.4 gallons.

If I divide miles driven by the refill quantity [456.1/9.4 = 48.5], will the monitor have the same figure [within a few tenths]?

I realize I'm never going to find point "X", but I also don't want to be kidding myself about the mileage I've been seeing on the screen. If the monitor has been telling me 50 mpg, I don't want to see 40 [or even 45!] when I fill up, but I need to know.

Thanks especially about the "gliding" info. I've been unwittingly defeating it even though I have noticed what I now know is the braking effect when taking my foot off the gas. I read the manual fairly closely and didn't read about ANYthing you wrote [which of course is why I asked!]. Now I know they don't want to overwhelm people with too much info, but you'd think they'd at least tell us about "gliding". Seems pretty important.

And OMG--the link to Omnipelagos--WHAT an unexpected treat!! Especially the info about "not living up to fuel efficiency claims ... due in part to ... driving style ... which requires..." things that I'd think every Prius driver needs to know. Before buying, I'd read some complaints from owners who definitely don't know/do those things. I'm sending the link to the physics teacher at my school!

I owe you at least a tank of gas! Where do I send it?

Dave Slomer

[MattInMD]

I've only had my prius for about 3 weeks, so I cannot speak defininitively about the monitor vs fill-up measured MPG. However, most folks claim the monitor is "slightly optimistic". The community-faq based owners guide claims this to be a difference of about 1.4mpg.


In my limited experience of one tank, I actually found the opposite.

You can find that guide at:
John's Stuff - Toyota Prius and more
It's currently on the main page as it had an update, but it's also in the left-side menus under "prius info" "User-Guide-H".

That's also a wealth of good information that John has collected from his own experience and the suggestions of others.

[dslomer]

I've had mine 10 days. Since the dealer filled it up [nice surprise], who knows how full it really was. So it'll take another fillup before I can measure.

And thanks, Matt, for the link to John's Stuff - Toyota Prius and more. Gee whiz!

Buying a Prius is not just buying another car, is it!? GOOD!

Dave

[MattInMD]

The dealer should have filled it up to be completely full.

Check your window sticker, it explicitly says you get a full tank of gas with the vehicle.

So while this is a "nice surprise" it's also something you're entitled to as a part of the sale.

So go ahead and measure at your first fillup. Bear in mind it's possible the dealer shorted you slighty, but that's doubtful.

Also, keep in mind that the prius gas tank has a bladder in it to control evaporation. This bladder does make "full" vary slightly, particularly when there's a big temperature difference between two fillups.

[dslomer]

"The dealer should have filled it up to be completely full."

Oh, all the fuel gauge bars were lit, so I'm sure it was "full"; I'm just saying "full" isn't always full. I used to be able to squeeze in another gallon or more before I learned that topping off isn't good.

And some pumps are a lot more sensitive than others. A few times I have had to go to another station when filling my truck's rear tank. I think it's the angle of the filler neck.

'So while this is a "nice surprise" it's also something you're entitled to as a part of the sale.'

I knew they USED to do it but it was the last thing on my mind when buying--for one thing, I was calculating that I would NOT get the full tax credit and a LOT more worried about THAT than $30 worth of gas! [Turns out I WILL get it since Congress upped a number on the 6251 form just enough for marginal me to get it all.]

I expected the gas deal had gone away because of the price, which, by the way, instead of heading toward $4 a gallon as "they" predicted in the weeks before I bought the car, is at $2.45 for 87 hereabouts. I expect it'll go up juuuust a bit, soon.

'tank has a bladder in it to control evaporation. This bladder does make "full" vary slightly, particularly when there's a big temperature difference between two fillups.'

Something else I didn't know till I read one of the links you provided. Didn't Kramer "invent" a bladder of sorts for oil tankers? When his prototype fell on Seinfeld's girlfriend, who was ignoring the "Hellooowww!" warnings, the plan fizzled.

Another link showed me how to defeat the infernal back-up beeping. Who the heck thinks up these schemes??

Dave

[schnickelfritz]

this is a tangential reply....

I hope you all realize that the gas prices are down to lessen the electorate's worries about the economy and improve the Republicans chances in November. Presumably, we Prius owners are sensitized to the environmental crisis the current administration has addressed so well!

Be sure to get out and vote (or vote early if your state allows) and get these bums some real opposition in Congress, to begin a rational and principled approach to the many problems facing the country, and to prepare for taking back the White House in 2008.

[SeaWolf34]

Originally Posted by schnickelfritz

this is a tangential reply....

I hope you all realize that the gas prices are down to lessen the electorate's worries about the economy and improve the Republicans chances in November. Presumably, we Prius owners are sensitized to the environmental crisis the current administration has addressed so well!

Be sure to get out and vote (or vote early if your state allows) and get these bums some real opposition in Congress, to begin a rational and principled approach to the many problems facing the country, and to prepare for taking back the White House in 2008.

I came to a Prius discussion thread and ran into a "get-out-the-vote" rally and a "rational and principled" oxymoron, all in the same sentence. r u uh refuge' from PriusChat?

[LifeTech]

Seawolf, I couldn't have said it better!!

LifeTech