concerns about the 40kWh pack

[ElSupreme]

Another factor with cold weather is that the air is much more dense, and therefore harder to move around the car. It isn't all battery temperature.

 

[Larry Chanin]

Just because I haven't seen it stated plainly: the reason the 40kwh battery in a Model S gets 160 miles but the Rav4 is only 100 miles is efficiency. The Model S is lighter and has much less wind resistance than a Rav4, so you get more miles at 55mph. Going 65+ will cut that down a goodly amount, so you might need to figure that in your calculations.

The post that seemed closest to this point, imho, was:

Hi Jason,

I agree that strider's information is useful.

However, fundamentally we have an apples and oranges situation here in comparing these two range numbers. Tesla has consistently been quoting an advertised range that is based on driving at a constant 55 mph. In contrast I believe that Toyota is quoting a range that will be close to the results of the new EPA 5-cycle test. If so, the primary reason for the differences in stated range is simply that the 5-cycle test is a more stringent test than driving at a constant 55 mph. When the final EPA numbers are released for both vehicles, I think we will find that in both cases the range will be a little over 100 miles with the Model S achieving better results due to superior aerodynamics, lighter weight and perhaps a more efficient power train.

Larry

 

[Larry Chanin]

From the 8-K Report just released:

The RAV4 EV marries the efficiency of an EV with the versatility of an SUV – in fact it is the only electric SUV on the market. With the largest battery pack of any non-premium EV, it is expected to have a city range of almost 170 miles, more than 60% above the Nissan Leaf. The electric RAV4 is a high performance version of the RAV4 with outstanding acceleration and excellent handling due to the low center of gravity afforded by the floor mounted battery pack

It goes without saying that city driving is at speeds less than 55 mph. :wink:

From Wikipedia:

[...]the "city" driving program or Urban Dynamometer Driving Schedule or (UDDS) is defined in 40 C.F.R. 86 App I and consists of starting with a cold engine and making 23 stops over a period of 31 minutes for an average speed of 20 mph (32 km/h) and with a top speed of 56 mph (90 km/h).

Here's a better reference from the Department of Energy

Larry

 

[mnx]

Model S Efficiency and Range | Blog | Tesla Motors

Looks like the 85kWh battery will do 225 miles @ 75mph. Extrapolate that to the 40kWh and you get 105 miles... You should be good to go (especially if you roll the windows down instead of cranking the A/C)

Thats two of us. If I can charge in standard mode, and know that I will go 100 miles without worrying about how I drive, will be completely satisfied with the 40 kWh Model S.

 

[dsm363]

Model S Efficiency and Range | Blog | Tesla Motors

Looks like the 85kWh battery will do 225 miles @ 75mph. Extrapolate that to the 40kWh and you get 105 miles... You should be good to go (especially if you roll the windows down instead of cranking the A/C)

That is almost certainly range mode though. Anytime they talk about a maximum range, I think they are assuming you charge in range mode. For Rifleman's use, I think you should really look at the 60 kWh pack since I imagine you plan to keep the car for a number of years and that will give you plenty of buffer space in your range when the battery pack starts to decrease slowly many years from now.

Windows down also decrease range but I think less that windows up and heavy AC use. These are the factors from the blog post they are assuming to get max range:

Constant speed (such as using cruise control)
Flat ground, no wind
Climate control OFF or using vent only (no heat or air conditioning)
300 lbs of vehicle load (driver plus passenger or cargo)
Windows up, sunroof closed
Tires inflated to recommended pressures
New battery pack (<1 year, <25,000 miles)

 

[mnx]

Agree on all points.

That is almost certainly range mode though. Anytime they talk about a maximum range, I think they are assuming you charge in range mode. For Rifleman's use, I think you should really look at the 60 kWh pack since I imagine you plan to keep the car for a number of years and that will give you plenty of buffer space in your range when the battery pack starts to decrease slowly many years from now.

 

[Larry Chanin]

Model S Efficiency and Range | Blog | Tesla Motors

What really has me concerned is the Rav4 EV. It has a slightly bigger battery, is less aerodynamic, but probably weights only a little more. It is advertising a 100 mile real world range. Let's assume the Model S 40KW is not going to do much better, since it is internally very similar. If the Model S only has a 115 mile range, and I loose 20% of that when not in range mode, I have 92 miles to work with. Right off the bat, one day a week must be in range mode just to complete my daily drive. The rumor I am hearing is that the battery is warranteed to be within 80% or original range. At the end of my warantee, I would be at about 73 miles range in standard mode. To give myself a little bit of leeway for error, I would have to charge in range mode every single charge. The end result would be a battery that is useless shortly after the warantee runs up.

Thanks for the link.

That article states that the EPA 5-cycle range for the 85 kWh battery is 265 miles, extrapolating to a 40 kWh battery the range would be 125 miles, if the same cells were used in both models. Since the 40 kWh pack may use a different cells this 125 mile range may be slightly overstated. It is however is comparable to the 100 mile range of the RAV4 EV in the sense we are consistantly comparing the same EPA range test.

Larry

P.S. If the 40 kWh battery pack uses the previous Panasonic cells we can expect the range to be reduced by about 92% due to the slightly lower energy density, resulting in an EPA range of 115 miles.

 

[jerry33]

That's what I do in my Volt though I am getting the 80kwh battery so I don't ever need to think about routes. I just get in and go! In my Volt while I am not 'tethered' by battery range I do enjoy the pureness of the EV mode and will take the slower route often to eek out as much battery range as possible.

That strategy really works (especially if the temperatures are high). Prius example:

DATE__________ODO____INC_____AVG
-- High temperatures start here
06/28/10____109831____637____67.6 (3.5)
07/28/10____110452____620____67.9 (3.5)
08/10/10____111064____611____67.2 (3.5)
--- Trip to NE starts here
08/13/10____111690____625____59.8 (3.9)
08/14/10____112308____618____60.0 (3.9)
08/20/10____112972____663____64.2 (3.7)
08/22/10____113411____438____58.9 (4.0)
08/31/10____113922____510____61.8 (3.8)
--- Trip to NE ends here
-- High temperatures end here
09/24/10____114560____637____70.5 (3.3)

 

[brianman]

@jerry33 - decoder ring needed

 

[jerry33]

@jerry33 - decoder ring needed

Oops. Forgot to put the column headings. Edited now.

 

[Norbert]

Thanks for the link.

That article states that the EPA 5-cycle range for the 85 kWh battery is 265 miles, extrapolating to a 40 kWh battery the range would be 125 miles, if the same cells were used in both models. Since the 40 kWh pack may use a different cells this 125 mile range may be slightly overstated. It is however is comparable to the 100 mile range of the RAV4 EV in the sense we are consistantly comparing the same EPA range test.

Larry

P.S. If the 40 kWh battery pack uses the previous Panasonic cells we can expect the range to be reduced by about 92% due to the slightly lower energy density, resulting in an EPA range of 115 miles.

While a lower energy density means that the 40 kWh pack might be heavier than would be proportional, it still has less weight altogether, since it is smaller. This increases the range, as one can see from the @55 mph range, which is 160 miles, instead of about 140 miles (as would be proportional to the 300 miles / 85 kWh pack).

We can assume that *about* the same factor (160/300) applies to the 5-cycle range, which would mean that the 5-cycle value for the 40 kWh pack would be around 265 * (160/300) = 141 miles per charge.

 

[Larry Chanin]

While a lower energy density means that the 40 kWh pack might be heavier than would be proportional, it still has less weight altogether, since it is smaller. This increases the range, as one can see from the @55 mph range, which is 160 miles, instead of about 140 miles (as would be proportional to the 300 miles / 85 kWh pack).

We can assume that *about* the same factor (160/300) applies to the 5-cycle range, which would mean that the 5-cycle value for the 40 kWh pack would be around 265 * (160/300) =141 miles per charge.

Hi Norbert,

Yes, I agree the lighter battery pack might offset the reduction in kWh. However, we now know that the 55 mph range of the 85 kWh battery is 320 miles, not 300 miles.


So if the 40 kWh pack uses the same cells as the 85 kWh pack then comparing our different approaches we get the following for the estimated EPA 5-cycle range:

265 * (160/320) = 133 miles

or

265 * (40/85) = 125

Larry

 

[EVNow]

Based on the differences in how the batteries are conditioned between the two cars do you think that the Model S's range might not be as sensitive to winter driving?

I had always assumed (like most others, I guess) that active thermal management would increase the range in winter, compared to passive management. Volt's reported cold weather range has put doubts in my mind. Roadster owners have also suggested losing range.

In Leaf we lose range - both thr' use of heater and also just because of the cold (when not using heater). Model S would certainly lose range when using the heater - the question is, how does it work in cold weather with no heater. Will the range lost because cold battery be greater or lesser than the energy needed to heat the battery ? Ofcourse, we also don't know the temperature characteristics of the cells they will use.

In any case, I'd conservatively say, cold weather driving on freeway will significantly shorten the range compared to ideal (160 miles) and also to the EPA range (may be 10 to 20% less than EPA).

 

[Larry Chanin]

In any case, I'd conservatively say, cold weather driving on freeway will significantly shorten the range compared to ideal (160 miles) and also to the EPA range (may be 10 to 20% less than EPA).

Thanks for your response.

It's interesting to note that one of the cycles in the new EPA test is taken at a temperatue of 20 degrees F that also requires the use of the heater, so this is partially factored into the composite EPA number.

Larry

 

[Norbert]

Hi Norbert,

Yes, I agree the lighter battery pack might offset the reduction in kWh. However, we now know that the 55 mph range of the 85 kWh battery is 320 miles, not 300 miles.


So if the 40 kWh pack uses the same cells as the 85 kWh pack then comparing our different approaches we get the following for the estimated EPA 5-cycle range:

265 * (160/320) = 133 miles

or

265 * (40/85) = 125

Larry

As I said in the RAV4 thread (it would be good to reduce this discussion to one thread), the 320 miles number is for the EPA 2-cycle test. In case the @55 mph numbers were to change, they would likely change for both packs and the ratio would remain the same. So I am still at 141 miles per charge (265 * 160 / 300) as an estimate for the 5-cycle range of the 40 kWh pack.

 

[Larry Chanin]

As I said in the RAV4 thread (it would be good to reduce this discussion to one thread), the 320 miles number is for the EPA 2-cycle test. In case the @55 mph numbers were to change, they would likely change for both packs and the ratio would remain the same. So I am still at 141 miles per charge (265 * 160 / 300) as an estimate for the 5-cycle range of the 40 kWh pack.

The New RAV4

Larry