mitch672
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Re: 100 miles?

Thu Apr 29, 2010 8:37 am

"Where did you get 19.2kwh ?"

I think he did %80 of 24KWh, which is 19.2KW of availble power before the Leaf is "empty"

assuming they won't allow the battery pack to discharge below %20 SOC, which of course we don't know yet, but is a fairly good assumption
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AndyH
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Re: 100 miles?

Thu Apr 29, 2010 8:40 am

Another look at energy use VS. speed - from the internal combustion world.

This chart is compiled from data collected by hundreds of VW diesel drivers that are part of tdiclub.com.
Image

The first thing to point out is that it's 'upside down' compared with the Tesla watt hour per mile chart because it's a 'miles per unit of energy' chart instead of a 'unit of energy per mile' chart. Notice that the highest fuel economy for a range of different models (Jetta, Golf, Beetle, Passat have different colors) happens at 35mph?

While the absolute fuel economy - energy per mile - changes from a bit over 60 to 90 miles per gallon, the speed for highest economy (lowest energy use) happens at the same speed - regardless of vehicle size, drag, or weight (again - within this group of diesel powered VWs).

When an EV manufacturer says a car gets best range at 35 they're simply reflecting the laws of physics, not necessarily a misguided marketing department. It's common for electric scooter manufacturers, for example, to give a 'max range' number, and a 'max speed' number. The max range will happen at about 35 mph - and unless one has a downhill commute both ways :) they'll not get that same range at 55mph.

Just like with a gas car - if you need to get another 10 miles out of the 'tank' to make that fuel station, turn off the AC, slow down, and crank-up your hypermiling skillz. :D

Andy
Last edited by AndyH on Thu Apr 29, 2010 9:32 am, edited 1 time in total.

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EVDRIVER
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Re: 100 miles?

Thu Apr 29, 2010 8:52 am

AndyH wrote:Another look at energy use VS. speed - from the internal combustion world.

This chart is compiled from data collected by hundreds of VW diesel drivers that are part of tdiclub.com.
Image

The first thing to point out is that it's 'upside down' compared with the Tesla watt hour per mile chart because it's a 'miles per unit of energy' chart instead of a 'unit of energy per mile' chart. Notice that the highest fuel economy for a range of different models (Jetta, Golf, Beetle, Passat have different colors) happens at 35mph?

While the absolute fuel economy - energy per mile - changes from a bit over 60 to 90 miles per gallon, the speed for highest economy (lowest energy use) happens at the same speed - regardless of vehicle size, drag, or weight.

When an EV manufacturer says a car gets best range at 35 they're simply reflecting the laws of physics, not necessarily a misguided marketing department. It's common for electric scooter manufacturers, for example, to give a 'max range' number, and a 'max speed' number. The max range will happen at about 35 mph - and unless one has a downhill commute both ways :) they'll not get that same range at 55mph.

Just like with a gas car - if you need to get another 10 miles out of the 'tank' to make that fuel station, turn off the AC, slow down, and crank-up your hypermiling skillz. :D

Andy



There will be a standard at some point for relative comparison or every MFG would use statistics that benefit their vehicle range not real driving under a unified scale. If ICE MFG could use this rational it would be impossible to calculate MPG against various vehicles. Once the EV standard is in place on a sticker there will be big differences between what was stated and what will be a standard. This is about marketing, does anyone think that if Nissan does not have a standard they are REQUIRED to use that they will chose a method that gives them a lower number? No. I'm sure we will see all this change in the future.
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AndyH
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Re: 100 miles?

Thu Apr 29, 2010 9:19 am

EVDRIVER wrote:I would say closer to 70 with acceptable pack temps, no headwind or grades @ 65 mph. How do you get 250 wh/mile at 70? That's assuming the car consumes 250 at all speeds which is not accurate and making these comparisons to the Tesla is not a very accurate measure at highway speeds. That is an extremely low penalty to pay at highway speeds and the Leaf does not have astonishing aerodynamics. Since the Leaf has 19.2kwh to work with, even if it only consumed 250wh per mile that would be 76.8 miles best case. Remember, the car cycles to 80% DOD and it's quite sly to state a range based on 100% DOD and lowest possible consumption cycle.


I suspect we don't have to take another 20% off the Leaf pack size for our range guestimates. I say this because we aren't told how many gallons of fuel our fuel tank actually holds but how much is usable. Same for cell phone and laptop batteries - the battery might be capable of 4 1/2 hours of use but the management system is programmed to only allow 4 hours of talk time.

Nissan says in their literature that the battery holds 24KWh. Reports from Leaf tour attendees suggest that Nissan is only allowing us to use the pack from 90% state of charge to 10% state of charge - they're already derating the pack to 80%. This means that the 100% we see on our fuel gauges is only 80% of what the battery can provide.

The battery is LiMn - which is fully charged at about 4.1V. The battery manufacturer lists 14.4V for a 4-cell module - only 3.6V per cell. That confirms for me that the manufacturer is already understating cell capacity - which seems to reinforce that we are likely to have all 24KWh available for our use.

If we can keep our consumption at 240wh/m, 100 mile range should be achievable.

Lithium cells perform better when hot - so we're likely to have longer range from a full pack in the summer.
Capacity drops when cold. If the pack isn't heated, rang will drop in the winter (unless the pack is over sized a bit to give us all-season performance)
Capacity will drop as the battery ages. Minimum range can be maintained for a longer time by oversizing the pack.
Energy use will go up in the winter because cold air is more dense - more aerodynamic drag.
All the other effects of wind, driving style, passenger/cargo weight, terrain, and tire inflation apply as well.

Andy

AndyH
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Re: 100 miles?

Thu Apr 29, 2010 9:26 am

EVDRIVER wrote:There will be a standard at some point for relative comparison or every MFG would use statistics that benefit their vehicle range not real driving under a unified scale. If ICE MFG could use this rational it would be impossible to calculate MPG against various vehicles. Once the EV standard is in place on a sticker there will be big differences between what was stated and what will be a standard. This is about marketing, does anyone think that if Nissan does not have a standard they are REQUIRED to use that they will chose a method that gives them a lower number? No. I'm sure we will see all this change in the future.


That is exactly why the LA4 and other STANDARD test cycles exist!

What are we really saying when we bash use of LA4? Do we WANT Nissan to join the 'Chinese scooter' crowd and report 'max range' (at an unknown speed with an unknown driver weight, unknown air density, unknown tire pressure, etc.) or do we want to know a number that can be directly compared against another vehicle?

Another example of this is the standard fuel mileage numbers on stickers for ICE vehicles. We all know that we can get very different numbers on the road depending on how we drive. But that STANDARD was created so that consumers can make a direct comparison without having to slog thru marketing BS.

Andy

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mwalsh
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Re: 100 miles?

Thu Apr 29, 2010 9:54 am

evnow wrote:Having said that, everyone needs to assess how sustainable a lifestyle that needs 70 to 80 miles of commute a day really is. Major CO2 reductions that are needed to save the planet (no hyperbole here) do not come about without any lifestyle changes.


But the change I'd rather make, over giving up my "relatively easy and very well compensated job with a long commute", would be to go EV and recharge with solar.

Edit: Oh, I suppose moving house, closer to work, would be the next best thing. Except that work is in a crappy neighborhood.
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garygid
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Re: 100 miles?

Thu Apr 29, 2010 9:58 am

I think the point was not that Nissan did not use SOME standard (LA4), but that they could choose ANY test that was convenient for their purposes from the several available "standards" (LA92, etc.).

At least, they told us which standard test they used.
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Bicster
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Re: 100 miles?

Thu Apr 29, 2010 12:07 pm

I did some Googling and couldn't find any definitive information supporting the 80% DoD assumption.

Edit: I missed AndyH's comments, which make sense - thanks.
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LTLFTcomposite
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Re: 100 miles?

Thu Apr 29, 2010 12:11 pm

evnow wrote:Major CO2 reductions that are needed to save the planet (no hyperbole here) do not come about without any lifestyle changes.


CO2, schmee-O2, people aren't interested in making lifestyle changes to save the planet. Only solutions that enhance our lifestyles need apply.
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mwalsh
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Re: 100 miles?

Thu Apr 29, 2010 12:16 pm

From a first drive review on Edmunds 'Inside Line' web site "Moreover, the Leaf will top 90 mph, but it won't travel 100 miles at that sort of speed — 60 miles is more like it, we're told.". So assuming that feedback came from Nissan, I would think that some of the numbers posted here are not all that far off the mark.
2011 Blue Ocean SL with 75,000 miles.
2015 pack under warranty 12/30/15.
Tinted windows.
Bridgestone Ecopia 422+ tires.
L1 EVSE upgrade.
FIAMM horns.
Superbright LED lighting.
2013 sun visors.
LED shifter.
Heated seats.
GT-R map lamp lenses.
AV L2 EVSE.

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