Jack Rabbit Starts

[idunk]

"This graph shows the efficiency of the electric power train" - so that presumable includes the inverter efficiency, but I don't know if that includes or excludes battery efficiency.

Generally speaking, when manufacturers and tier 1s talk about electric power-train, the battery is included, althugh 95% efficiency looks a bit too high to me.

 

[highcountryrider]

You're not alone. Today a red Mustang pulled up in the lane to the left of me at a red light.
She had that "I'm going to beat you out and then cut you off" look.

She TRIED. :roll: :twisted:

I am having a lot of fun with the 'zippy' (but safe) starts, and passengers are always pleasantly surprised with the acceleration.

All of my other cars, I never rested my head on the headrest. But one day, I had to 'race' this ICE that was showing off, so I floored it (left him waaay behind) and hit my head hard against the headrest as did my passenger. I've never had a car including my Celica GT-S that did that so now I'm getting used to resting my head back and noticed it's much more comfortable than any other because it's not so far back. Have you had this happen yet? :lol:

 

[bradleygibson]

Wow--you guys must have gotten a different model than I did, 'cuz mine's not *that* fast...

Our other car--a dino-burner--is a 2005 Subaru Outback XT. My wife was dying to switch cars the other day and I had to drive the Subaru. While I absolutely love the Leaf, there is no way (IMHO) it would be a match for the Subaru.

I don't know about these Mustangs, but I didn't think the Outback was particularly fast (perhaps because my brother drives an STI and an Audi S4...) There are tons of Leafs in Woodinville, I suppose we could try one evening to see if my impressions are correct...

 

[TickTock]

I was reading 375V on the battery at idle and it dropped to 355V at full accelleration. Current was 239A so 239*(375-355)=4.8kW. So we are only losing 5kW in the battery to deliver 85kW --> 94% efficiency. This doesn't count wire losses (I think - depends on where the battery voltage is sensed), etc, but avoiding friction braking (100% loss) is far more important.

 

[highcountryrider]

I have yet to see a road-legal ICE that can beat my LEAF off the line.
(Noise excluded.)

Wow--you guys must have gotten a different model than I did, 'cuz mine's not *that* fast...

Our other car--a dino-burner--is a 2005 Subaru Outback XT. My wife was dying to switch cars the other day and I had to drive the Subaru. While I absolutely love the Leaf, there is no way (IMHO) it would be a match for the Subaru.

I don't know about these Mustangs, but I didn't think the Outback was particularly fast (perhaps because my brother drives an STI and an Audi S4...) There are tons of Leafs in Woodinville, I suppose we could try one evening to see if my impressions are correct...

 

[JustinC]

I have yet to see a road-legal ICE that can beat my LEAF off the line.
(Noise excluded.)

I guess you haven't been challenged by any real performance cars then. The Leaf is quick, but let's face it, 0-60 in 7 seconds is not that great. Try a Porsche 911 GT3 that gets there in half the time. I think the Leaf feels faster than it is because you have all that torque up front mated with the spongy suspension of a family car. It feels like you might bounce off the road if you hit a speed bump while accelerating.

That said, I am pleased with the quickness, and I agree there is some value in showing the kids in ICE cars that an electric car is fast and fun.

 

[planet4ever]

I have yet to see a road-legal ICE that can beat my LEAF off the line.
(Noise excluded.)

I guess you haven't been challenged by any real performance cars then. The Leaf is quick, but let's face it, 0-60 in 7 seconds is not that great.

Who said anything about 0-60? Which, by the way, the LEAF can't do in 7 seconds. We're talking "off the line", "jack rabbit starts". Think a city street with a speed limit of 25 or 35.

Now, I doubt if I could beat a Porche to even 25 if it was really trying, but we've gotten off the topic. The question is not whether the LEAF is the fastest, but whether there is a mileage penalty in trying to be. There is obviously a mileage penalty in using friction brakes. There is clearly also a penalty in using regen when you don't have to, since regen can't be 100% efficient. And jack rabbit starts are often associated with car-pitching stops, though they don't really have to be. What is not at all obvious, at least to me, is when and whether a jack rabbit start uses more energy.

Look at that power train efficiency graph again back on page 1 of this thread. The less time you spend under 20 mph the less time you are going to be down at that 85% efficiency level. Now, admittedly, the more torque you use the faster you have to go to get up over 90% efficient, but that's a very steep slope, so you don't have to go much faster. On the other side of the coin, the faster you accelerate the more time you are going to spend at whatever maximum speed you are aiming for, and that means more time fighting the maximum air resistance you will encounter. How important that is depends heavily on what your maximum speed will be. I doubt if it matters at 25 mph.

So (heresy!) is it perhaps more efficient to accelerate quickly to 25 than to use the LEAFfan 1-bubble strategy?

Ray

 

[LEAFfan]

So (heresy!) is it perhaps more efficient to accelerate quickly to 25 than to use the LEAFfan 1-bubble strategy?
Ray

Since I hit 6.6m/kW h on the dash tonight only using zero to one bubble to reach 30-40mph on an 18 mile trip, I'm going to doubt that anyone can use the 'accelerate quickly' method to do better, but it would be an interesting challenge. How many bubbles would you use to get to 30 (rarely stop at 25)? I'll give it a try and see what happens.

 

[highcountryrider]

Sounds a bit like my cousin's theory that you get better gas mileage if you drive
faster, because you spend less time on the road. :roll:

As for ICE vs electric.
"It goes from 0 to 60 in 3 seconds! In fact, it can take a quarter-mile in 11.46 seconds reaching a top speed of 114 mph – that’s a world record. And it’s street-legal."

 

[DaveEV]

I have yet to see a road-legal ICE that can beat my LEAF off the line.
(Noise excluded.)

I guess you haven't been challenged by any real performance cars then. The Leaf is quick, but let's face it, 0-60 in 7 seconds is not that great.

Who said anything about 0-60? Which, by the way, the LEAF can't do in 7 seconds. We're talking "off the line", "jack rabbit starts". Think a city street with a speed limit of 25 or 35.

Now, I doubt if I could beat a Porche to even 25 if it was really trying, but we've gotten off the topic.

Seriously - they weren't trying if you beat them to 30 mph by any significant margin. Or your LEAF is faster than mine for some reason.

Had a look at Insideline for full road tests - first non-sports car I came to in the list was the Kia Optima Hybrid. Curb weight 3641 lbs, 166 hp 4-cyl engine and 30 kW motor.

0-30 in 3.1s
0-45 in 5.4s
0-60 in 8.4s (8.0s w/1ft of rollout)

Compared to the LEAF (107 hp, 3354 lbs):
0-30 in 3.4s
0-45 in 6.0s
0-60 in 10.0s (9.6s w/1ft of rollout).

Not even close, and the Kia Optima Hybrid isn't even a fast car.

Quickly looked up a few other cars - most 4cyl cars are basically the same as the LEAF - 6cyl or 4cyl-turbo cars are all significantly faster.

 

[bradleygibson]

I have yet to see a road-legal ICE that can beat my LEAF off the line.
(Noise excluded.)

Wow--you guys must have gotten a different model than I did, 'cuz mine's not *that* fast...

Our other car--a dino-burner--is a 2005 Subaru Outback XT. My wife was dying to switch cars the other day and I had to drive the Subaru. While I absolutely love the Leaf, there is no way (IMHO) it would be a match for the Subaru.

I don't know about these Mustangs, but I didn't think the Outback was particularly fast (perhaps because my brother drives an STI and an Audi S4...) There are tons of Leafs in Woodinville, I suppose we could try one evening to see if my impressions are correct...

Well, I'm game! I did a couple of neutral drops on the way home today, and it felt quick, but I feel that my Subaru pulls much harder. Maybe its psychological--all the noise--but I'd be interested to "get to the bottom of this" if anyone is interested...

Car is stock and I am not a professional.

-Brad

 

[bradleygibson]

...

Now, I doubt if I could beat a Porche to even 25 if it was really trying, but we've gotten off the topic.

Seriously - they weren't trying if you beat them to 30 mph by any significant margin. Or your LEAF is faster than mine for some reason.

Had a look at Insideline for full road tests - first non-sports car I came to in the list was the Kia Optima Hybrid. Curb weight 3641 lbs, 166 hp 4-cyl engine and 30 kW motor.

0-30 in 3.1s
0-45 in 5.4s
0-60 in 8.4s (8.0s w/1ft of rollout)

Compared to the LEAF (107 hp, 3354 lbs):
0-30 in 3.4s
0-45 in 6.0s
0-60 in 10.0s (9.6s w/1ft of rollout).

Not even close, and the Kia Optima Hybrid isn't even a fast car.

Quickly looked up a few other cars - most 4cyl cars are basically the same as the LEAF - 6cyl or 4cyl-turbo cars are all significantly faster.[/quote]

Agreed.

And re:the original topic, yes, of course there is going to be a drop in efficiency, as no system is going to be perfectly linear in performance.

Some of the justification used for this question though (ie. the carbon emitted in the manufacture of solar PV's) is questionable, though, as the solar panels don't know that extra juice is going into your battery from the jack-rabbit starts. Put another way, the panels won't wear out any faster because your battery needs more charge; they'll make the same amount of electricity regardless of how much you use.

-Brad

 

[highcountryrider]

I was speaking of off-the-line. Many ICE cars can beat me to 30, but not to 10.

But ain't that Datsun impressive? I saw a piece on TV about it. I'll bet that car surprises
a few folks.

Back to topic, I'm almost sure, by common sense rule, that rapid starts use a bit more
energy, but I don't think it's much and I certainly don't concern myself about it. Other
than doing it safely.

(I keep seeing that woman in the Mustang talking to her mechanic. "What do you mean
it's running fine! I was beaten out by an econo-box!! Fix it!" :lol: )

 

[Nekota]

...snip stuff...

Look at that power train efficiency graph again back on page 1 of this thread. The less time you spend under 20 mph the less time you are going to be down at that 85% efficiency level. Now, admittedly, the more torque you use the faster you have to go to get up over 90% efficient, but that's a very steep slope, so you don't have to go much faster. On the other side of the coin, the faster you accelerate the more time you are going to spend at whatever maximum speed you are aiming for, and that means more time fighting the maximum air resistance you will encounter. How important that is depends heavily on what your maximum speed will be. I doubt if it matters at 25 mph.

So (heresy!) is it perhaps more efficient to accelerate quickly to 25 than to use the LEAFfan 1-bubble strategy?

Ray

Power losses follow I^2 times R so high levels of current will dissipate more power in the form of heat than lower current levels. If the circuits have a positive temperature coefficient of resistance, then this adds additional heating levels. One may argue the time at higher power levels is shorter such that the integrated power (energy or area under the curve) is the same but the power delivered to the motor is I times V so higher levels of acceleration (high current) are less efficient than lower levels.

LeafFan's high mileage numbers are an example of avoiding I^2 heating losses on acceleration and regeneration.

 

[ElectricVehicle]

The thing is, with a LEAF, even grandma can get peak acceleration by dropping the pedal to the floor, no hesitation, no shifting. And no engine roar, so it's smoother and you don't get the idea that the vibrating gas engine is going to rip itself part at wide open throttle, and the gas engine will survive but it sure sounds like something bad might happen.

So you get to 10 mph, and you've zipped put fast enough, that you've demoralized most gassers from even trying at the point, besides, they know if they do..... they'll.... have.... to... PAY FOR IT at the GGGAASSSss STATION!! :shock:

And it feels really futuristic LEAFing all of those gas burners in your rear view mirror. I did it once yesterday, and I left them all half a block behind me, like 800 feet. Only one caught up to me a quarter mile later after I had settled into my 45 MPH cruise for most of the way. So they didn't know they were in a drag race, so what? It was still fun - open road in front of me, gas cars LEAFT behind!

Of the 2 dozen cars behind, there must have been at least one person who recognized the LEAF as an Electric and didn't know they could accelerate that fast - it ain't no golf cart!

(Disclaimer - exercise extreme caution when LEAFing gas cars behind. This demonstration was conducted by a non-professional driver on an open course in broad daylight on dry pavement with no children in the vicinity, no traffic head and only after verifying that traffic not in the direction of travel had already come to a full and complete stop with no open lanes for a potential red light runner.)

 

[TickTock]

...And no engine roar, so it's smoother and you don't get the idea that the vibrating gas engine is going to rip itself part at wide open throttle, and the gas engine will survive but it sure sounds like something bad might happen.

There's the nut. Most drivers don't like to redline their cars. It's obnoxious, loud, and strains the engine. The main advantage Leafers have is we can redline the engine with no discernable noise. Make no mistake, though, we are straining the drive train. I know that the brushless motors used for RC airplanes do see a significant reduction in available power over time when run full throttle (due to the permantent magent on the rotor getting demagnetized from the heat). It is reasonable to assume a similar threat applies to the LEAF motor. Then there's the battery and motor controller also getting strained beyond the "typical" stress levels used by the engineers for reliability simulations. I, too, love the jack-rabbits starts but try to save them for special occasions.

 

[highcountryrider]

<snip>gas cars LEAFT behind!<snip>

I love it! Can I use that?

<snip>...love the jack-rabbits starts but try to save them for special occasions.

Yep.

 

[QueenBee]

love the jack-rabbits starts but try to save them for special occasions.

Agreed, but I still don't feel that the original question has been answered with a high level of certainty. Sure it'll increase temperatures and is more stressful but in the grand scheme of things my guess is that is minimal since you can go full throttle for very long before you are going 90 I think the additional loss on the wires is going to minimal as a percent. The question I have is how does the efficiency of the motor, inverter and battery change at the higher amperages? The chart from the manual doesn't help answer that.