Justification for 300 mile battery

[Norbert]

The article goes on to indicate the most likely long term is 50% cost decreases after about 15 years (see Figure 12).

Figure 12 has three scenarios. The "pessimistic" and "baseline" scenario obviously don't apply to Tesla, since at 2012 the predicted pack prices for a 85 kWh pack (300 mile battery) would be $60k and above for the pessimistic version. That's obviously not the case for Model S. The baseline scenario at least comes down to a realistic price in the future, but only after 2020, for the 2012 Model S. Unless Panasonic is giving Tesla a 50% rebate, or so.

According to the "optimistic" scenario, the price for the 300 mile battery pack would be $34k, which is certainly closer to the truth. But according to this scenario, the price wouldn't be halved even in 20 years. Given how completely unrealistic the other scenarios are (for Tesla), I think this one isn't very convincing either.

 

[ckessel]

Given how completely unrealistic the other scenarios are (for Tesla), I think this one isn't very convincing either.

Granted, though I'm trying to justify expectations with data, which was sort of the whole driver behind "justify the 300 mile battery" question. Both stopcrazy and I have pointed to links (with whatever issues they may have) that seem to indicate the near future (5-10 years) doesn't show large jumps in battery tech. Are there any studies that show differently?

 

[Larry Chanin]

When taking a long road trip how many travel at 55 mph? :wink:

Using the Roadster's performance characteristics we can achieve the EPA mileage of 244 miles by traveling at a constant speed of 55 mph. However, here in Florida the average motorist travels at 80 mph. Traveling at a constant speed of 80 mph the Roadster only achieves an ideal range of 150 miles, or about 61% of its EPA range.


So if the Model S has similar performance characteristics as the Roadster the ideal range for a new "300" mile battery pack would be reduced to about 184 miles when traveling at 80 mph. After 5 years that range might only be about 129 miles when traveling at 80 mph.

Likewise, a new "160" mile battery would have a range of less than 100 miles at 80 mph or less than 70 miles after 5 years.


Larry

 

[stopcrazypp]

Granted, though I'm trying to justify expectations with data, which was sort of the whole driver behind "justify the 300 mile battery" question. Both stopcrazy and I have pointed to links (with whatever issues they may have) that seem to indicate the near future (5-10 years) doesn't show large jumps in battery tech. Are there any studies that show differently?

Perhaps not as quick as EVNow's prediction of 2x density in 5 years (except maybe with a major breakthrough). But if Panasonic can maintain the ~8%/year trajectory, in 5 years, density will be 1.08^5 = 1.47x. It'll take 9 years to reach double density.

Extending my previous graph:

Year Actual Projected(8%/yr) miles(tied with "Actual" where possible, "Projected" when no "Actual" figure)
2009 2.9ah 2.900ah
2010 3.1ah 3.132ah 300
2012 3.4ah 3.653ah 329
2013 4.0ah 3.945ah 387
2014 x.xah 4.261ah 412
2016 x.xah 4.970ah 481
2018 x.xah 5.797ah 561
2019 x.xah 6.261ah 606 <- doubling point
2020 x.xah 6.762ah 654

 

[Eberhard]

When taking a long road trip how many travel at 55 mph? :wink:

Using the Roadster's performance characteristics we can achieve the EPA mileage of 244 miles by traveling at a constant speed of 55 mph. However, here in Florida the average motorist travels at 80 mph. Traveling at a constant speed of 80 mph the Roadster only achieves an ideal range of 150 miles, or about 61% of its EPA range.


So if the Model S has similar performance characteristics as the Roadster the ideal range for a new "300" mile battery pack would be reduced to about 184 miles when traveling at 80 mph. After 5 years that range might only be about 129 miles when traveling at 80 mph.

Likewise, a new "160" mile battery would have a range of less than 100 miles at 80 mph or less than 70 miles after 5 years.


Larry

Its not easy to compare the Roadster with the Model S in the behave of consumption. The Model S is quite heavier but has a better aero. This means the rolling resistance is higher, but the air resistance grow slower with increasing speed compared to the roadster.
Roadster cw = 0.37 Model S is between 0.22 and 0.27. Model S is doing better at higher speed, but will have always a higher consumption then the Roadster.

But back to the theme. The 300miles version will have more then the double lifetime compared to the 160miles version because of putting less stress to the battery while having nearly the double capacity. I guess the lifetime of the 160miles is 160milesx500cylces = 80.000 miles at 70% SOC the 300miles to 300x500x1.5 = 225.000 or 10 years. If you drive less then 20.000miles/year better go for the 160 or 230miles version. Otherwise the calendar degradation of the batterie will be higher as by use.
My Roadster clocks now 59.000km after one year (18 Nov. 2010)

 

[ckessel]

Perhaps not as quick as EVNow's prediction of 2x density in 5 years (except maybe with a major breakthrough). But if Panasonic can maintain the ~8%/year trajectory, in 5 years, density will be 1.08^5 = 1.47x. It'll take 9 years to reach double density.

Thanks, that's more or less what I've been led to believe, that we'll have a nice, steady improvement. At least until the next giant leap in battery tech gets proved out and makes it to mass market, which even if the discovery happened today would probably take the better part of a decade to make it into an EV.

 

[Larry Chanin]

Its not easy to compare the Roadster with the Model S in the behave of consumption. The Model S is quite heavier but has a better aero. This means the rolling resistance is higher, but the air resistance grow slower with increasing speed compared to the roadster.
Roadster cw = 0.37 Model S is between 0.22 and 0.27. Model S is doing better at higher speed, but will have always a higher consumption then the Roadster.

Hi Eberhard,

Yes, it is true that the Roadster and Model S won't have identical range versus speed performance. However, as you point out, despite having a better Coefficient of Drag the Model S is heavier, and of course what you didn't mention is the Model S has a much larger cross-sectional area. So it is possible that the Model S might actually have a higher loss of range at high speeds. Perhaps this is the point you were making (highlighted above) which supports the thrust of my remarks.

To recap the point I was attempting to make is that there will be a significant drop off in range with speed when going from 55 mph to 80 mph using the Roadster performance characteristics to put us in the ballpark. When range is a concern, as in the case of a long road trip, the vast majority of drivers will be traveling at high speeds where range suffers the most. So while the loss won't be precisely 61% as in the case of the Roadster, nevertheless it will be quite significant and perhaps even worse than the Roadster. There will be enough of a loss to certainly justify upgrading to the larger battery pack for anyone who periodically expects to do any long road trips at realistic highway speeds.

In summary, the range of a "300" mile battery pack will be nowhere near 300 miles at realistic highway speeds.

Larry

 

[stopcrazypp]

In summary, the range of a "300" mile battery pack will be nowhere near 300 miles at realistic highway speeds.

Larry

The accuracy of that claim will largely depend on if the "300" number is under the same conditions as the "245" number for the Roadster (the more lax pre-2008 EPA testing), or if it is under the newer testing (the same one that gave 73 miles to the Leaf, 35 miles to the Volt, 32 miles to the Karma). If it's the former, then that would be true. If it's the latter, then "300" won't be too far off from "realistic range"

I'm not going to try to guess at the CdA again, the last discussion using preliminary Model S numbers arrived at the conclusion that it'll range from slightly better than the Roadster to about 20% worse (depending on what numbers you use):
http://www.teslamotorsclub.com/showthread.php/5929-More-aero-Roadster-or-Model-S

 

[dsm363]

Wouldn't they have to use the newer EPA testing method since the car is hitting the market in 2012?

 

[Larry Chanin]

The accuracy of that claim will largely depend on if the "300" number is under the same conditions as the "245" number for the Roadster (the more lax pre-2008 EPA testing), or if it is under the newer testing (the same one that gave 73 miles to the Leaf, 35 miles to the Volt, 32 miles to the Karma). If it's the former, then that would be true. If it's the latter, then "300" won't be too far off from "realistic range"

Hi,

I believe that IF the "300" mile range was based on the newer, more rigorous EPA testing method, then there is no way Tesla would have failed to point out that very significant fact.

Here is a relevant excerpt from Tesla's most recent 10-K filing:

Any changes to the Federal Trade Commission’s electric vehicle range testing procedure and recent changes made by the United States Environmental Protection Agency’s energy consumption regulations for electric vehicles could result in a reduction to the advertised range of our vehicles which could negatively impact our sales and harm our business.

The Federal Trade Commission (FTC) requires us to calculate and display the range of our electric vehicles on a label we affix to the vehicle’s window. The FTC specifies that we follow testing requirements set forth by the Society of Automotive Engineers (SAE) which further requires that we test using the EPA’s combined city and highway testing cycles. The EPA recently established new requirements for the fuel economy stickers that appear on new cars offered for sale (i.e., the Monroney label). In addition to the new labels and as part of that final rule published on July 6, 2011, EPA has also modified its testing cycles in a manner that, when applied to our vehicles, could reduce the advertised range of our vehicles by up to 30% as compared to the combined two-cycle test currently applicable to our vehicles. While we intend to demonstrate to the EPA that a more appropriate derating factor applies to our vehicles, there is no guarantee that the EPA would approve such a factor. These new requirements apply to all model year 2013 and later vehicles. Following EPA’s announcement, the FTC also issued an Advanced Notice of Proposed Rulemaking seeking comment from interested stakeholders as to whether that Federal Agency should adopt procedures similar to EPA’s under its labeling requirements. In the meantime, the FTC has also published an Enforcement Policy noticing that the FTC would forebear enforcement against any vehicle manufacturer that utilized labels meeting the new EPA requirements versus the existing FTC requirements. This indicates FTC’s inclination to move towards harmonization of their labeling requirements with EPA’s new requirements. If the FTC continues in this direction, this could impair our ability to deliver the Model S with the initially advertised range, which could result in the cancellation of reservations that have been placed for the Model S. Any reduction in the advertised range of our vehicles could negatively impact our vehicle sales and harm our business.

From these statement there's no question that the testing for the Model S' advertised range is consistent with the Roadster's more lax EPA testing.

Therefore, for folks doing a lot of highway driving it would be very ill-advised to make a battery pack size decision expecting a range anywhere near 300 miles, when driving at realistic highway speeds.

Larry

 

[Eberhard]

Tesla claims, that the drivetrain of the Model S will be more efficient than the Roadsters one. But despite this fact, all losses including rolling resistance but except air drag may count for 60% of overall losses at the speed of 55mph while the Roadster is about half to half. If you increase the speed to 80mph, the losses in air drag is more then the double. While the roadsters overall losses increases to 156%, the Model S only to 145%. Model S is more efficient at higher speeds then the Roadster. But with the Roadsters low base of the consumption, Model S will never catch up even at higher speeds.

 

[AnOutsider]

Didn't elon say at the event that their testing was on the new EPA (not sure if he said 2 or 5 cycle testing)?

 

[dsm363]

I hope the new EPA testing cycle produces realistic numbers. I don't see why there isn't a city, highway and combined range for EVs instead of one number. I assume Tesla has to advertise the EPA number so the unrealistic EPA numbers simply hurt EVs when in reality people most people don't achieve the EPA numbers in ICEs too.

 

[Norbert]

Wouldn't' they have to use the newer EPA testing method since the car is hitting the market in 2012?

Not necessarily at this point. GM used 40 miles for a long time, and Nissan on its website still presents "100 miles" as the first number you see. They add that it is according to the LA4 cycle "EPA LA4 test cycle: 100 miles", But then they add that it "has a range of 138 – 62 miles" with further explanations. The 73 number comes only in small print in the Disclaimers, on the page I am looking at right now ("the basics" after clicking on "range").

There seem to be both possibilities, but in my calculations I use the Roadster graph for different constant speeds and then multiply by 300/245. However Elon has indicated that the range may be between 310 and 320. I guess for going from constant speed to driving at various speeds, one always needs to consider the specific conditions on a case-by-case basis, but for me, in those cases where the range matters, I'd think that my speed is rather constant. And I'll probably get the Aero wheels (hopefully, in a sense).

 

[Doug_G]

Granted, though I'm trying to justify expectations with data, which was sort of the whole driver behind "justify the 300 mile battery" question. Both stopcrazy and I have pointed to links (with whatever issues they may have) that seem to indicate the near future (5-10 years) doesn't show large jumps in battery tech. Are there any studies that show differently?

It's kinda crazy to point to any chart of battery improvements and use it as an indication of the future. People are just too used to Moore's law. With silicon technology it's fairly easy to point to reduced line widths as a clear path to lower cost per transistor, higher density, and higher speed. There's no such thing for batteries. It's all chemistry, and you're exploring solution space in a more-or-less random fashion (at best educated guessing) trying to optimize multiple competing goals.

 

[Dave EV]

From these statement there's no question that the testing for the Model S' advertised range is consistent with the Roadster's more lax EPA testing.

Therefore, for folks doing a lot of highway driving it would be very ill-advised to make a battery pack size decision expecting a range anywhere near 300 miles, when driving at realistic highway speeds.

Are Tesla's estimated ranges performed using the same test as Nissan uses with the 100 mile LA4 LEAF estimate? Anyway, I personally find that the EPA adjusted range (73 miles) is closer to reality than the LA4 number, especially if one wants to leave about 10 miles buffer "just in case". Drove 70 miles yesterday with about 50 of those miles on the freeway at 60-65 mph, the rest city streets and got home with about 5 miles on the DTE indicator which is what I expected (not quite a 100% charge, though).

Model S is more efficient at higher speeds then the Roadster.

Without knowing the CdA of either car (not just the Cd) it's impossible to guess which one will be more efficient at higher speeds. As stopcrazypp pointed out, most estimates put both cars within spitting distance of each other when calculating CdA.

 

[stopcrazypp]

There seem to be both possibilities, but in my calculations I use the Roadster graph for different constant speeds and then multiply by 300/245.

That's probably a good approach. Such a graph would be useful to guessing the Model S range.

Another shot at guessing EPA sticker numbers assuming 85kWh capacity for the Model S (ignoring for the moment EPA sticker is wall-to-wheel, not battery-to-wheel; that only makes the guess more conservative). All EPA stickers have already been adjusted to the new stricter cycle, AFAIK.
(Model S Target): 28kWh/100miles -> 303 miles
Roadster: 30kWh/100miles -> 283 miles
Leaf: 34kWh/100miles -> 250 miles
Volt: 36kWh/100miles -> 236 miles
Smart ed: 39kWh/100miles -> 218 miles
Karma: 65kWh/100miles -> 131 miles (Highly unlikely Model S is as horrible as the Karma).

 

[Larry Chanin]

Are Tesla's estimated ranges performed using the same test as Nissan uses with the 100 mile LA4 LEAF estimate?

Hi,

The way I interpret the Tesla 10-K statements is that both the Roadster and the advertised Model S ranges used the old two-cycle (city & highway) EPA test. I don't know for sure what test Nissan used, but EPA has used a computational method that multiples the two-cycle results by .7 to approximate the 5-cycle results. Since the Leaf went from a range of about 100 miles to about 70 miles this suggests that perhaps the ~100 mile range was using the same two-cycle used by Tesla on the Roadster and Model S advertised range. Rather than conducting a new series of 5-cycle tests perhaps this simple calculation was permitted in lieu of the actual tests.

Without knowing the CdA of either car (not just the Cd) it's impossible to guess which one will be more efficient at higher speeds. As stopcrazypp pointed out, most estimates put both cars within spitting distance of each other when calculating CdA.

Yes, I think we've gotten into the weeds here. I repeat, we don't need to know the precise numbers here to be reasonably certain that when driving at realistic highway speeds, the Model S is not going to deliver the initial advertised ranges. I feel the Roadster performance numbers are good approximations to give us an educated guess as what our range will be at various constant speeds to help us in selecting the appropriate battery size pack for our anticipated driving needs.

Larry

 

[EVNow]

The way I interpret the Tesla 10-K statements is that both the Roadster and the advertised Model S ranges used the old two-cycle (city & highway) EPA test. I don't know for sure what test Nissan used, but EPA has used a computational method that multiples the two-cycle results by .7 to approximate the 5-cycle results.

Nissan advertised 100 miles @ LA4 but leaf achieves that in combined cycle.

I assumed S will similarly get a 30% cut in EPA rating. So, the 160 would be actually 130. (correction - I used the m/kwh of Leaf's 73 miles range to get 130.)

My Leaf experience is that EPA number is a good approximation of highway driving, with cold weather reducing the range further.

 

[Dave EV]

I assumed S will similarly get a 30% cut in EPA rating. So, the 160 would be actually 130.

30% of 160 is 112 mi, not 130. 130 mi is more like 19% cut.