EV Benefit

daniel · 08-31-2004, 05:07 PM

I believe that I am getting a slight but significant improvement in mpg by judicious use of the EV switch. I have no hard data, and I welcome comments about why I am wrong. But here is my theory:

I believe that the car is reluctant to charge the battery over 6 bars. Yes, it will do it, but I believe it prefers to maintain that space. I believe this because in winter, when the ICE runs continuously to provide heat for the cabin, it still seldom goes over 6 bars. It will sometimes hit 7, but rarely. The ICE will be running, the instantaneous mileage will be not all that great, but it still hovers around 6 bars, occasionally 7.

My commute is 4 miles. I am halfway there, and already up to 6 bars even if I started out with only 3, by the time the ICE is warm enough to go into Stage 4 (full hybrid) operation, which is more efficient; but I still have 1/4 of my commute ahead of me before I'll hit a traffic light, and maybe be able to stop and enter S4 operation, and if the lights are all green I'll never get past S3 operation. The SOC will stay up around 6 bars.

My judicious use of EV consists of the following: If my SOC is at 6 bars and I still have not entered S4 (S4 determined by the ability go go to electric operation by lifting off the pedal and then applying gentle pressure - known as "feathering") then I will engage EV mode until I'm back down to 4 bars, or until I need to accelerate faster to avoid annoying the drivers behind me. Also, as I approach home I will use EV mode as needed (if needed) to avoid parking with more than 4 bars showing, so that there's plenty of battery capacity available to take the charge that will be generated, like it or not, during the warm-up stage the following morning.

I am currently at 47.8 mpg for the present tank, and though this would be nothing to brag about for a normal Prius driver, it is my best tank ever, and I think it is quite respectable for the very short length of my commute. I installed Costal Tech's EV mode around the time of my last fill-up.

froggdancer · 08-31-2004, 07:33 PM

And here I thought I was so clever for accidentally discovering "feathering."

So, is EV a way to force the car to run off of battery alone? I've been thinking there ought to be a switch for that? Where is it though? Or is it software? If it is software, will it void the warranty since the whole car is so computer based?

daniel · 08-31-2004, 07:58 PM

The Prius sold in Japan and in Europe has an EV button, which, as you suggest, forces the car to run on electric power only. The button was left off the US version, but all the software is in the car's computer. This article tells how you can install the button yourself. Costal Tech sells a kit to accomplish the same thing by pulling on the cruise-control stalk. There could be warranty issues, but most of us think that it would only be a problem if the switch or your installation of it caused the damage. And in the end, the switch is only invoking software that is already in the car, and is utilized in the factory version of the Prius sold elsewhere in the world.

Note, however, that speed, acceleration, and range are very limited in EV mode, since the electric motor and battery are normally only an assist to the gas engine.

**efusco** · 08-31-2004, 07:59 PM

Quote:

And here I thought I was so clever for accidentally discovering "feathering."

So, is EV a way to force the car to run off of battery alone? I've been thinking there ought to be a switch for that? Where is it though? Or is it software? If it is software, will it void the warranty since the whole car is so computer based?

New around here, aren't you....

Read This Article in the Knowledge Base to learn more....

daniel · 08-31-2004, 08:01 PM

Ha ha ha. We cross-posted.

hdrygas · 08-31-2004, 10:29 PM

Very interesting!!! When I drove my car home from Helena I expected to see a full battery. Those of you that have not been over western passes may not get this. These were the dreadful mountains that Louis and Clark wrote of. On a fairly good down hill with some runaway truck pull outs for truckers who have lost their brakes I could not get above 7 bars. I think this brings me to a closer understanding of the energy management. One wonders if anyone has "hacked" ( in the good sense of the word) the software of the Prius to determine how it does it's job. I wonder what language it was written in. Did they "do" their own OS or "borrow" one. I would love to look at the code. Maybe it is written is assembler. Does any one know what the CPU is? I am sorry I get wound up trying to understand how things work.

bruceha_2000 · 09-01-2004, 08:04 AM

Quote:

Maybe it is written is assembler.

Geez Henry, you must be as old or older than I am! Frankly, I doubt it written in assembler. memory and CPUs are plenty cheap enough to allow a little compiled code inefficiency to gain easy of coding and maintenance of the code. :-) I think they should give us the specs so we can create our own touch screen applications. Make it useful for things like turning off the reverse beeper and how the doors unlock!

I think Daniel is right. If used in specifically strategic ways, EV should be able to save a little bit of gas. As others have said before, the car doesn't know how long your trip will be or the terrain you will cover. For most people, the little bit of improvement wouldn't be worth the effort to figure out when they could use EV to advantage. But to others, it is FUN! (where is the geek emoticon?)

For FrogDancer, read through the site ( OK it will take WEEKS! ) That should take care of the dampness behind your ears :-) I learned and continue to learn an immense amount of useful information from PriusChat.

jchu · 09-01-2004, 10:13 AM

hdrygas,
Don't know who's OS it is or the chipset but a majority of vehicle computer in the US have previously run an OS designed by Wind River Systems (trades on NASDAQ under WIND) It is a small and very stable OS. As far as languages go, it seems to me that everything today is written in C. All of this is of course uninformed speculation.

bookrats · 09-01-2004, 02:55 PM

If I had a bet (and it would be a bet), I'd agree with jchu and say the firmware in the Prii was written in C. (With perhaps a caveat about the Prii display screen and its control being something else).

The company I work for writes embedded code for very, very small components -- very little RAM available. However, assembly is rarely, if ever, used; C is small enough (or in-line assembly code can be added in cases where you must shrink it down by a few 100 bytes.)

We've used C++ in some cases, but it's usually on instruments that we intend to be extensible, with software/features added to the instrument over time. (I.e., adding "software components" is conceptually easier with a OO language (and good design up-front)).

hdrygas · 09-01-2004, 11:42 PM

Lets see. My first language was Dartmouth Basic. Followed by Fortran. Then machine language and assembler for the Apple ][. Followed by Pascal. I had a Apple ][ with a language card 64k. Incredible. Remember loading programs with a cassette recorder in Apple Basic. Oh I learned that but not a great stretch for me. It all started because our college got a modem hook up to Dartmouth and only "Math majors" could handle it. They might consider applications by Physics majors. I was a poor dumb chem/bio major who was told I could not measure up. Four weeks later I was selling programs to do physics lab experiments. Never tell a dyslexic that they can't do something!

08-31-2004, 05:07 PM	#1
daniel Cat Lovers Against the Bomb Join Date: Feb 2004 Location: Spokane, WA Posts: 9,186 My Car: 2004 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	EV Benefit I believe that I am getting a slight but significant improvement in mpg by judicious use of the EV switch. I have no hard data, and I welcome comments about why I am wrong. But here is my theory: I believe that the car is reluctant to charge the battery over 6 bars. Yes, it will do it, but I believe it prefers to maintain that space. I believe this because in winter, when the ICE runs continuously to provide heat for the cabin, it still seldom goes over 6 bars. It will sometimes hit 7, but rarely. The ICE will be running, the instantaneous mileage will be not all that great, but it still hovers around 6 bars, occasionally 7. My commute is 4 miles. I am halfway there, and already up to 6 bars even if I started out with only 3, by the time the ICE is warm enough to go into Stage 4 (full hybrid) operation, which is more efficient; but I still have 1/4 of my commute ahead of me before I'll hit a traffic light, and maybe be able to stop and enter S4 operation, and if the lights are all green I'll never get past S3 operation. The SOC will stay up around 6 bars. My judicious use of EV consists of the following: If my SOC is at 6 bars and I still have not entered S4 (S4 determined by the ability go go to electric operation by lifting off the pedal and then applying gentle pressure - known as "feathering") then I will engage EV mode until I'm back down to 4 bars, or until I need to accelerate faster to avoid annoying the drivers behind me. Also, as I approach home I will use EV mode as needed (if needed) to avoid parking with more than 4 bars showing, so that there's plenty of battery capacity available to take the charge that will be generated, like it or not, during the warm-up stage the following morning. I am currently at 47.8 mpg for the present tank, and though this would be nothing to brag about for a normal Prius driver, it is my best tank ever, and I think it is quite respectable for the very short length of my commute. I installed Costal Tech's EV mode around the time of my last fill-up. __________________ Daniel ---------------------- Primary car: Zap Xebra SD: 100% electric car. 1.9 cents per mile, using electrons generated from water power. (The Prius is my gas guzzler, used when I have to travel farther than 35 miles in a day.) "If voting changed anything, they'd make it illegal." -- Emma Goldman "Anyone who has ever looked into the glazed eyes of a soldier dying on the battlefield will think long and hard before starting a war." -- Otto von Bismarck

08-31-2004, 10:29 PM	#6
hdrygas Senior Member Join Date: May 2004 Location: Olympia Wa Posts: 3,650 My Car: 2004 Prius Package: #9 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Very interesting!!! When I drove my car home from Helena I expected to see a full battery. Those of you that have not been over western passes may not get this. These were the dreadful mountains that Louis and Clark wrote of. On a fairly good down hill with some runaway truck pull outs for truckers who have lost their brakes I could not get above 7 bars. I think this brings me to a closer understanding of the energy management. One wonders if anyone has "hacked" ( in the good sense of the word) the software of the Prius to determine how it does it's job. I wonder what language it was written in. Did they "do" their own OS or "borrow" one. I would love to look at the code. Maybe it is written is assembler. Does any one know what the CPU is? I am sorry I get wound up trying to understand how things work. __________________ Belle, a Millennium Silver '04 BC #9 "Becoming one with my Prius, ICE on ICE off" Belle has been passed on to my daughter. I have a new silver Prius 08. No name yet we have just met but not been introduced.

09-01-2004, 02:55 PM	#9
bookrats Senior Member Join Date: Mar 2004 Location: Seattle, WA Posts: 2,843 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	If I had a bet (and it would be a bet), I'd agree with jchu and say the firmware in the Prii was written in C. (With perhaps a caveat about the Prii display screen and its control being something else). The company I work for writes embedded code for very, very small components -- very little RAM available. However, assembly is rarely, if ever, used; C is small enough (or in-line assembly code can be added in cases where you must shrink it down by a few 100 bytes.) We've used C++ in some cases, but it's usually on instruments that we intend to be extensible, with software/features added to the instrument over time. (I.e., adding "software components" is conceptually easier with a OO language (and good design up-front)). __________________ "Have you ever noticed.... Anybody going slower than you is an idiot, and anyone going faster than you is a maniac?" -- George Carlin</span> Jeff Meyer <span style=\'color:green\'>Tideland '05 AM Package, 12 November 2004

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08-31-2004, 07:33 PM	#2
froggdancer Join Date: Aug 2004 Location: Pasadena, California Posts: 11 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	And here I thought I was so clever for accidentally discovering "feathering." So, is EV a way to force the car to run off of battery alone? I've been thinking there ought to be a switch for that? Where is it though? Or is it software? If it is software, will it void the warranty since the whole car is so computer based?

08-31-2004, 07:58 PM	#3
daniel Cat Lovers Against the Bomb Join Date: Feb 2004 Location: Spokane, WA Posts: 9,186 My Car: 2004 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	The Prius sold in Japan and in Europe has an EV button, which, as you suggest, forces the car to run on electric power only. The button was left off the US version, but all the software is in the car's computer. This article tells how you can install the button yourself. Costal Tech sells a kit to accomplish the same thing by pulling on the cruise-control stalk. There could be warranty issues, but most of us think that it would only be a problem if the switch or your installation of it caused the damage. And in the end, the switch is only invoking software that is already in the car, and is utilized in the factory version of the Prius sold elsewhere in the world. Note, however, that speed, acceleration, and range are very limited in EV mode, since the electric motor and battery are normally only an assist to the gas engine.

08-31-2004, 08:01 PM	#5
daniel Cat Lovers Against the Bomb Join Date: Feb 2004 Location: Spokane, WA Posts: 9,186 My Car: 2004 Prius Package: #6 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Ha ha ha. We cross-posted.

09-01-2004, 10:13 AM	#8
jchu Join Date: Mar 2004 Location: Nampa, ID Posts: 1,063 My Car: Package: Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	hdrygas, Don't know who's OS it is or the chipset but a majority of vehicle computer in the US have previously run an OS designed by Wind River Systems (trades on NASDAQ under WIND) It is a small and very stable OS. As far as languages go, it seems to me that everything today is written in C. All of this is of course uninformed speculation.

09-01-2004, 11:42 PM	#10
hdrygas Senior Member Join Date: May 2004 Location: Olympia Wa Posts: 3,650 My Car: 2004 Prius Package: #9 Nominated 0 Times in 0 Posts TOTM Awards: 0 Friends: 0	Lets see. My first language was Dartmouth Basic. Followed by Fortran. Then machine language and assembler for the Apple ][. Followed by Pascal. I had a Apple ][ with a language card 64k. Incredible. Remember loading programs with a cassette recorder in Apple Basic. Oh I learned that but not a great stretch for me. It all started because our college got a modem hook up to Dartmouth and only "Math majors" could handle it. They might consider applications by Physics majors. I was a poor dumb chem/bio major who was told I could not measure up. Four weeks later I was selling programs to do physics lab experiments. Never tell a dyslexic that they can't do something!