2015 LEAF specs - no range increase

[TimLee]

When did Nissan lose their mind :?:
Lying about range by eliminating 80% charging :?:
"Madness!... Madness!"

 

[Nubo]

That graph would seem to indicate that a two speed transmission, with a low gear for city driving, would help significantly by reducing 'lugging' of the drive motor. It would help to see a graph of consumption vs speed as well. A simple two-speed, low-friction transaxle, combined with more sophisticated software management of power consumption, could still add range. In that case the higher gear ratio could also be somewhat higher, allowing less consumption at freeway (65-75MPH) speeds. So instead of having a compromise sweet spot of about 45MPH, you'd have one at about 30MPH and one at, hopefully, 55-60MPH...

There may be a place for transmissions in EVs for performance cars or wringing out ultimate range. But personally the single-speed approach is incredibly attractive for its simplicity and ease of use. And recall that Tesla originally planned on a 2-speed transmission. Unfortunately, despite a lot of engineering effort, 1st gear kept getting shredded by the low-end torque.

 

[LeftieBiker]

Tesla was building a performance car. I think a 2 speed transaxle could handle the Leaf's detuned motor, with the right Low ratio.

 

[DaveinOlyWA]

Tesla was building a performance car. I think a 2 speed transaxle could handle the Leaf's detuned motor, with the right Low ratio.

correct answer to the wrong question. maybe we should consider that if not building a performance car, multiple gears are not necessary in an EV. gearing increases speed performance, not range performance.

 

[LeftieBiker]

Tesla was building a performance car. I think a 2 speed transaxle could handle the Leaf's detuned motor, with the right Low ratio.

correct answer to the wrong question. maybe we should consider that if not building a performance car, multiple gears are not necessary in an EV. gearing increases speed performance, not range performance.

Gearing can do either, or both - that's what ratio optimization is about. If the Leaf is, as it appears from the graph, wasting power at both low speeds and freeway speeds, then designing the transmission to provide optimum motor speed at those two points would help both low speed acceleration and overall range, if the driver exercises restraint.

 

[evnow]

I'm fairly sure they could tweak the drivetrain to give the car an actual 100 mile range, by limiting both acceleration and top speed to reasonable figures, and keeping the motor near peak efficiency at most speeds.

You can't go from 84 to 100 by minor tweaks.

Acceleration and top speed don't matter much in standardized cycles.

 

[LeftieBiker]

I'm fairly sure they could tweak the drivetrain to give the car an actual 100 mile range, by limiting both acceleration and top speed to reasonable figures, and keeping the motor near peak efficiency at most speeds.

You can't go from 84 to 100 by minor tweaks.

Acceleration and top speed don't matter much in standardized cycles.

I wrote "actual 100 mile" not "EPA rated 100 mile." If consumption can be reduced at the two most common speeds driven, range will improve by more than a tiny bit.

 

[TimLee]

If consumption can be reduced at the two most common speeds driven, range will improve by more than a tiny bit.

There just isn't much room for cost effective improvement when the lowest efficiency point is already at 84% or greater.
Both Nissan and Tesla recognized this and went with a single speed gear ratio.
Nissan did slightly improve range and efficiency in 2013, but it was very modest and they did it by limiting peak torque.

 

[Nubo]

Tesla was building a performance car. I think a 2 speed transaxle could handle the Leaf's detuned motor, with the right Low ratio.

correct answer to the wrong question. maybe we should consider that if not building a performance car, multiple gears are not necessary in an EV. gearing increases speed performance, not range performance.

Gearing can do either, or both - that's what ratio optimization is about. If the Leaf is, as it appears from the graph, wasting power at both low speeds and freeway speeds, then designing the transmission to provide optimum motor speed at those two points would help both low speed acceleration and overall range, if the driver exercises restraint.

For common driving, the amount of time spent in the less-efficient zones is limited.

At low speeds the car is already highly efficient due to low aerodynamic drag. The most efficient speed seems to be somewhere between 10 and 15 mph. Most driving isn't at those speeds, but if you do, range at those speeds approaches 150 miles, iirc.

Low-speed/high-torque regime solves itself, as your speed will increase and take you into the efficient zone.

Normal cruise speeds and torque conditions put you in the efficient zone, by design.

High speed/low torque is rare and would only be when slowing or descending a hill.

A transmission could add some efficiency especially if the driver is committed to take advantage of it or if it were automated. But it wouldn't be that significant for most owners. It would add complexity and weight. A manual gearbox would depend on the driver's technique to gain efficiency meaning it could be little or none, or even decreased efficiency. An automatic or controlled CVT would add even more weight, complexity and cost all for not much gain. The reduction gearbox seems almost bullet-proof which is a good benefit. I don't recall reading of anyone needing repairs to that component. Go to an owners' forum for other vehicles and transmission complaints are often rampant. I find that a lot of strengths of the car lie in what it *doesn't* have, and a transmission is one of those.

 

[DaveinOlyWA]

Tesla was building a performance car. I think a 2 speed transaxle could handle the Leaf's detuned motor, with the right Low ratio.

correct answer to the wrong question. maybe we should consider that if not building a performance car, multiple gears are not necessary in an EV. gearing increases speed performance, not range performance.

Gearing can do either, or both - that's what ratio optimization is about. If the Leaf is, as it appears from the graph, wasting power at both low speeds and freeway speeds, then designing the transmission to provide optimum motor speed at those two points would help both low speed acceleration and overall range, if the driver exercises restraint.

gearing adds weight, drag, complexity, additional friction points in order to gain what? how much efficiency does a well built electric motor lose?

I guessing nowhere near enough to justify the expense.

 

[LeftieBiker]

Nissan obviously wasn't very concerned with drag when they designed the Leaf, and could easily reduce it even with a two speed transaxle. Friction increase would be tiny. Weight increase also small. Electric motors with no transmission are great for limited speed ranges. When you want high efficiency over a 10-95MPH spread, you're stretching it too far. You can have the last word.

 

[davidcary]

Nissan and Tesla and I think every other EV maker has concluded that a single speed is all an EV needs. Even Tesla with top speed of 130 still went with a "1 speed".

So they are wrong and you are right?

 

[GRA]

Nissan and Tesla and I think every other EV maker has concluded that a single speed is all an EV needs. Even Tesla with top speed of 130 still went with a "1 speed".

So they are wrong and you are right?

Since most BEVs are limited range cars best suited for shorter commutes at lower speeds, doing away with a transmission makes sense. But for high speed highway driving, a transmission may be less expensive, lighter and consume less space as well as being quieter than a bigger battery pack.

Tesla gave up on the two speed transmission for the Roadster because they couldn't get it to handle the torque, not because it was a bad idea. It's noticeable just how quickly the BMW M5 is overhauling the Model S at 100 mph in their video drag race. For autobahn driving I suspect Tesla may well need a multi-speed transmission if they're to compete with the other luxury cruisers in Germany - I wonder just how limited the Model S' range is at 100+ mph. Whether German Model S sales are low because of high German electricity prices, customer chauvinism, lack of performance/range or all three I don't know.

There are certainly many companies out there developing multi-speed transmissions for BEVs, the only question is whether the transmission provides the same additional range at a lower cost (but with greater complexity and likely higher maintenance) than bigger batteries, and what relative value customers put on each.

 

[JeremyW]

I thought Tesla was going to use just a different reduction gear for the German market? Might have to use only the P85 inverters though. I mean, even the spark with it's low reduction (slow speed) motor seems to be the way things are going. Just have to make bigger stator windings, beefier inverters... and batteries with a touch less internal resistance (or higher pack voltages).

To me, it seems like just making more powerful, low speed, high torque motors ends up being the better investment in improving both acceleration and top speed. I think the losses through a transmission would be higher in all but a few edge cases. That few % of efficiency gain is swamped by the huge aerodynamic losses of high speed driving. Just make things a bit more aerodynamic!

 

[SalisburySam]

Apparently, in survey-speak, "Would you like an EPA range of ~150 miles for an extra ~$5000?" actually means "Would you like a different shade of blue?"

Thanks NYLEAF for making my day! I read this and it really gave me clarity, a chuckle, and a first entry in the no doubt soon-to-be-announced survey decoder ring.

 

[jelloslug]

Nissan obviously wasn't very concerned with drag when they designed the Leaf, and could easily reduce it even with a two speed transaxle. Friction increase would be tiny. Weight increase also small. Electric motors with no transmission are great for limited speed ranges. When you want high efficiency over a 10-95MPH spread, you're stretching it too far. You can have the last word.

Tesla started out with a two speed gear reduction in the Roadster and quickly changed it over to a single speed.

 

[GRA]

Nissan obviously wasn't very concerned with drag when they designed the Leaf, and could easily reduce it even with a two speed transaxle. Friction increase would be tiny. Weight increase also small. Electric motors with no transmission are great for limited speed ranges. When you want high efficiency over a 10-95MPH spread, you're stretching it too far. You can have the last word.

Tesla started out with a two speed gear reduction in the Roadster and quickly changed it over to a single speed.

And the reason they did so was mentioned in my post three above yours, and Nubo's post back one page.

Edit: Here's just one example of a multi-speed transmission for EVs, the claimed range improvement vs. cost, and a similar debate among posters as to its value (Naturally, take all manufacturer claims with an appropriately sized pile of salt, unless it's verified by an independent party):

"New 3-speed EV powertrain to offer 10-15% improvement in EV range"

http://www.greencarcongress.com/2014/02/20140219-dsd.html#more" onclick="window.open(this.href);return false;

 

[evnow]

I wrote "actual 100 mile" not "EPA rated 100 mile." If consumption can be reduced at the two most common speeds driven, range will improve by more than a tiny bit.

"Actual 100 mile" makes no sense. Actual for who - in what conditions etc etc ?

Heat pump was a good example of "actual" reduction in consumption without affecting EPA numbers, BTW.

 

[QueenBee]

Nissan and Tesla and I think every other EV maker has concluded that a single speed is all an EV needs. Even Tesla with top speed of 130 still went with a "1 speed".

So they are wrong and you are right?

That tends to be his M.O. He knows more about this then you and them combined.

 

[LeftieBiker]

I wrote "actual 100 mile" not "EPA rated 100 mile." If consumption can be reduced at the two most common speeds driven, range will improve by more than a tiny bit.

"Actual 100 mile" makes no sense. Actual for who - in what conditions etc etc ?

Heat pump was a good example of "actual" reduction in consumption without affecting EPA numbers, BTW.

Since you already understand that the EPA rating doesn't accurately reflect all driving conditions, and that changes can affect actual range without affecting EPA range, I guess all that I have to explain is that by "actual 100 mile" I meant "a 100 mile range attainable under good but not exceptionally good circumstances by most drivers." I don't have much interest in arguing for the sake of arguing. Carry on without me.