EV Question

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I drove my father's Studebaker in a parade last month and it occured to me that it would be pretty sweet of a local Prius club was in a parade, all in EV mode. The parades I've driven are less than 2 miles and the speed isn't more than 5mph.

 

Clarifying further:

"Forced" EV mode (i.e. with button) in Europe - 28mph (=30mph indicated)
"Forced" EV mode (i.e. with button) in US - 34mph
Automatic "EV mode" - 41mph

 

With a very functional and sensible search function that this
bboard has, I cannot understand why there's ANY debate about this.
.
_H*

 

I do it all the time when I round the corner toward home where it's all private streets, especially the one-lane straightaway. Saves me the trouble of pushing a button that doesn't let me go as fast.

 

I was speaking of from a dead stop, like an intersection. Way too hard to do without spending a ton of time babying it...

 

If we were in a perfect world, where there were no conversion inefficiencies and no friction of any kind, it wouldn't matter if you accelerated by EV or ICE, the energy needed would be the same.

But you are working with power and energy. Energy is, well, energy needed to get to where you are going, no matter how fast you try to get there. To get to a particular speed requires the same amount of energy, no matter the acceleration.
Power is the amount of energy delivered over a period of time. Quick acceleration needs more power than a slow acceleration, even if the same energy is needed. The battery can only deliver so much power. If any additional power is needed, the ICE has to get involved. Sure, you could accelerate to 42MPH without ICE, but you'd be accelerating very slowly. There is a point where ICE is needed for the extra power.

Ideally, since the law of motion says an object in motion will stay in motion until acted upon by an outside force, a car would get infinite miles per gallon at cruising speed. However due to mechanical and wind friction, we all know this is not the case. Since much of the time we are cruising, the MPG we see here is what we think as the 'normal' MPG. The 'lousy' MPG we see at acceleration is the same energy we would need even if we used pure electric. We would understand this better if instead of miles per gallon, we used miles/KWH, whether that KWH was from gas or electricity. Though electricity is a form of energy, it isn't an originating source of energy in the Prius' closed system. You don't put electricity in the car, you put gas. Sometimes that gas is converted to electricity, hopefully when that is the most efficient thing to do to utilize the energy you need, whether to propel the car, cool it, or stop it.

Now add to the simple physics friction and inefficiencies. Electric motors can deliver a lot of torque (force) even at 0 speed. ICE cannot deliver much torque or power at low RPMs, and can't even do its job at all at 0 RPM. Motors can.
Then you have to add other quirks about ICE. They need to be very hot to be efficient. Since they warm up themselves, there has to be a time when they will be inefficient. When they are off, they are cooling down, thus losing their ability to continue operating efficiently when needed. That's the nature of heat engines. Unfortunately, heat engines are the best way to deliver lots of power.

So, is it a good idea to use the EV button? That all depends on the total waste due to inefficiences during the time or miles you are evaluating.

Lets take a round trip that's 3 miles one way. In the situation where you don't use EV, you get 35 MPG both ways because you are in the inefficient mode that tries to warm up the ICE. You use .17 gallons of gas for the round trip.
Now for one leg, you use EV. So for 3 miles you don't use any gas. The other 3, you don't use EV, to recharge the battery. Since ICE is now charging the battery as well as warming itself up, you now get 30 MPG. You now used only .1 gallons of gas. Assuming at the end of this trip the battery SOC is the same as when you started your round trip, using EV is more efficient. In reality, I don't know if the battery would be back to the same SOC it started with this short of a trip.
However, usually the energy (gas) it takes to recharge the battery is more than the energy you got out of the battery for EV. EV is more efficient when the conversion loss is less that the ICE's waste or loss if you didn't use EV. This would probably be the case when on short trips when ICE is still cold, and/or very low speeds with low power demand.

 

And here is the US measurements to support the 34mph :
http://www.vassfamily.net/ToyotaPrius/CAN/evcancindex.html

 

DanMan, I took some measurements ( I was really curious about regeneration efficiency ) and the result is quite stunning, which means I need an other pair of eyes to show me where I might have failed to spot a mistake; a "veteran", who can point at my errorous logic :

I switched to EV mode, accelerated to 50km/h, than regen braked 'til stopped. If I measured amp/voltage, I got ~50% regen. ( Let's not talk about the fact, that the SOC sometimes even went up 1 unit... )

http://www.vassfamily.net/ToyotaPrius/CAN/eveffindex.html

Any comments? ( yes, I double checked the measurements, run tests 3 times, pretty much same result... ) What am I doing wrong? I can't believe that the Prius is THIS efficient...

 

What will the EV button do to my warranty in the US? I've found several occasions where I'm at the end of a trip, my engine is nice and warm and I'm at at or above 7 SOC's. I'm cruising on pure electric in the parking lot, but the person behind me is pushing me so I may a slight tap on the gas and suddenly my ICE won't shut off. This is where the EV button would be nice. Except if it's going to void my warranty.

 

Very nice explanation!......

I think he had the right idea about using the battery when the ICE would be at low ineffecient rpms and then charge it back at the higher speeds when the ICE is then in higher more effiecient rpms.

What he didn't factor in is the efficiency losses from the conversions.

To try and simplify the understanding abit at least for myself, I try to think of the battery as a reservoir for energy otherwise wasted. Then I can use that energy later.

With the EV button I can simply choose when to use it. If I try and use it for real hard core power, then like the above post, I must remember that has to be made back with gasoline.... unless I'm coming to a hill where I can make it back with wasted kinetic energy.

The electric, as stated in prior post is excellent for maintaining speed in coasting, at red lights, moving across a parking lot.... basically to do the extreme "light work" and "fill in the gaps" so the engine doesn't have to go to the trouble to fire up and heat up etc., nor does it have to run just to maintain the whimpy power needed to coast or sit still at a redlight.

Anything that cost only 55.00 on a car is a bargain..... you can't even buy one tire for that!

Its a fun toy as well as useful for special applications and just another cool tool for the techy prius user.

True, Toyota probrably left it out of the US cars because frankly our general populus is not as electronically astute as the Japanese, we are also sue happy, and expect perfection or we will complain. I think if I was Toyotas CEO, I would have left it out of the US too. Once we get used to the hybrids and our public gets better educated, they may can add it.

I don't blame the poster for trying to think of creative ways to use the EV.. I'm just a bit surprised he had the EV installed without first investigating and understanding its real use and advantages?... There is alot of good posts about this subject with some excellent suggestions and articles available on prius chat.

Some hate instructions and manuals and just like to figure it out on thier own, but they have no one to get upset with but themselves when they dont' understand.

There is a really good reason why we have to have a pilots license before we are allowed to get in to a plane and take it for a spin.

Good thing the EV switch is not too dangerous!

 

In my '06 Prius I can be cruising at 70+ mph and take my foot off the gas and lightly come back on and it will be in the "automatic EV" mode showing power only being drawn from the battery, and I've actually seen it do this at speeds as high as 70 mph. It is not very stable at all though, the slightest touch too far and the ICE kicks in, so it has to be a slight downhill while trying to maintain speed. I don't know if the '04-'05 Prius can do that?. I do however notice that when cruising ~40 mph and reaching 42 mph the ICE does kick on. I haven't noticed anything posted before on EV at speeds up to ~70 mph, has anyone else experienced this?

 

<div class='quotetop'>QUOTE(ilusnforc @ Sep 12 2006, 03:48 PM) [snapback]318563[/snapback]</div>

Yes I have! I don't think it's a true EV mode if what I've read is true. The ICE is supposed to be turning over at high speeds in order to avoid damage to the generators.

However, according to the MFD I can be cruising at high speed and still be getting "100 mpg" for short periods. :blink:

 

<div class='quotetop'>QUOTE(ilusnforc @ Sep 12 2006, 01:48 PM) [snapback]318563[/snapback]</div>

Its posted, just hard to find.. its called "super EV" or something like that.. basically it can't be done unless the battery is really charged... like after coming down a long hill or the like.... and yes a slight downhill grade greatly increases the liklihood to maintain it for more than a few seconds.
I assume "but don't know" that the older models perform the same.

 

super EV is when there is minimal gas being used and happens when going downhill. now, if you have the energy screen on, you and CANVIEW owners know that FREQUENTLY your mpg's will exceed 100 mpg which would lead one to believe no gas is being burned. that is not the case.

on my 2004 that had CANVIEW, i frequently could maintain mpgs at 100 mpg+ for up to 2 minutes at a time on some of the long slopes on I-5 and Hiway 512( just to name a few of the many hills here) but still be burning fuel at say .4 gph (gallons per hour) which @ 60 mph translates to 150 mpg.

so maybe not as efficient as we want to be but still very very good. just went to the Western Washington State Fair yesterday and as you enter town you drop down into the Puyallup River Valley which drains down from Mt. Rainer. i will be coasting in drive at 55 mph (driving this slow only because of the slope coming up) and still be doing over 65 mph at the bottom where i exit 4 miles later. yesterday (still on my first tank) was at the hill at 52.7 mpg and about 450 miles. hit the bottom at 454 miles and 53.3 mpg. well that does not make infinity mileage even under those circumstances. (will say that i have averaged as much as 400 mpg in that stretch before though)

 

Not only does the screen show 99.9 mpg but also on the Energy screen it shows the yellow arrows from the battery only, no orange arrows from the ICE... I do not have the CANVIEW, but I assume the ICE is just idling?

 

<div class='quotetop'>QUOTE(windstrings @ Sep 12 2006, 09:34 PM) [snapback]318731[/snapback]</div>

"Warp stealth" I think it's called. Should turn up more than a few hits on a search.

 

<div class='quotetop'>QUOTE(NuShrike @ Dec 5 2005, 10:00 PM) [snapback]168506[/snapback]</div>

Me too. I was all set to answer questions about EVs and how they accelerate better and more efficiently than any ICE. But alas, we're only talking about the ugly step-sister of real EVs - the Prius EV mode.

I know exactly where you're going with this, and I agree... but there is an important benefit of electric drive being left out here. Once you have made your electricity (with losses, etc) it takes FAR less energy to accelerate a mass with an electric motor than with an ICE. An ICE typically tosses 85% of its energy away in friction, while an electric motor only loses less than 10%. That's a HUGE difference. The problem here, is that we're first making our electricity with one of these terribly lossy ICE's!


<div class='quotetop'>QUOTE(driveprius @ Jan 2 2006, 08:52 PM) [snapback]183398[/snapback]</div>

Nothing.

This has been covered 1,245,645 times on this forum. It cannot void your warranty unless it breaks something that you wish to have covered under warranty. Nothing you can do to the car will simply "void the warranty." It has to first break something else... which the EV mod has never done, as far as I'm aware.

 

<div class='quotetop'>QUOTE(darelldd @ Sep 13 2006, 07:58 PM) [snapback]319280[/snapback]</div>

:lol: :lol: :lol: but whos counting?