40 kWh and 60 kWh EPA range estimates, and how will it effect defferals?

[Rifleman]

Well, after much soul searching, I have decided that if the 40 kWh has an EPA range of 120 miles in normal mode, I am going to go with the 40, otherwise, I will go with the 60. If I go with the 60, I will probably need to either lease or defer to save up a larger down payment.

The current dilemma is, with my reservation number, there is a chance that I will receive the email to configure before the first 40's are on the road, and I will have to configure before I know for sure if the 40 will do the job for me.

My question for any representative from Tesla is (and I know that they read this forum), when will the EPA estimates on range for the 40 and 60 kWh Model S's be released, and once they are released, will people who have already locked in a configuration be able to make a change or defer without penalty?

[ddruz]

Rifleman, this was my dilemma exactly. My number came up without enough hard information to make the kind of informed decision I prefer. I ordered the 60 kwh though at the end of the day the 40 kwh may meet all my range needs. I looked at the decision as buying insurance for an unknown risk, the unknown EPA range figures. This is not the way I like to do things.

I considered deferral but realized that even when the EPA numbers are in, and even if they indicated the 40 kwh would just make it for me, I still would not know with much certainty the parameters for battery degradation over time. So the 60 kwh again buys me insurance for an unknown risk, the unknown battery degradation over time. Since deferring could not eliminate this unknown for me I felt it was most prudent in my case to buy the 60 kwh.

I do hope, however, that Tesla will allow people to change their order when EPA numbers are known, as you suggest, for those folks for whom the battery degradation question is less of a question mark and the EPA ranges between the 40 kwh and 60 kwh are the biggest quandary.

[Doug_G]

I would ignore the EPA numbers, personally. They won't reflect real-world usage.

The performance numbers provided by Tesla are far more useful. Here's the range graph for the 85 kWh pack.



Tesla will no doubt provide similar information for the smaller packs, but for now just scale the numbers by the pack capacity - should be pretty darn close.

[jkirkebo]

Well, after much soul searching, I have decided that if the 40 kWh has an EPA range of 120 miles in normal mode, I am going to go with the 40, otherwise, I will go with the 60. If I go with the 60, I will probably need to either lease or defer to save up a larger down payment.

Well, 265/85*40=125 miles if the battery specs are correct. However, this could increase to maybe 130 miles because of lower weight since the 40kWh battery has fewer cells. I believe the chance for <120 EPA miles is quite low.

But this is in range mode. Normal mode being 85% of range mode, I seriously doubt you'd see much more than 110 EPA miles. So if 120 EPA miles in normal mode is your fixed goal, go for the 60kWh which should go around 160 EPA miles in normal mode. Then you have a buffer for 25% degradation too and SuperCharger access.

[Rifleman]

The real question when doing the math yourself is do you use the 85/40 ratio, or the 300/160 ratio. Unless there is a significant difference in pack weight, I simply do not know how a 85 kWh pack is rated for 300 miles, yet a 40 kWh pack is rated at 160 (less than half the size, more than half the range)

(265/85)*40= 124.7 Range Mode Range
(265/300)*40= 140.8 Range Mode Range

124.7*.85= 105.9 Standard Mode Range
140.8*.85 = 119.68 Standard Mode Range

I came up with the goal of 120 miles in standard mode because I drive 70 miles most days, and 90 once every other week or so (always known in advance, so range mode would be possible) I figure even with 20% battery degradation, I would be OK on range (and I could always drive a little slower, turn off HVAC, or charge in range mode to give a little extra buffer near the end of the batteries life).

I really am hoping that the 40 kWh Model S can go more than 100 miles in normal mode without hypermiling, if it cannot, it really will mean that the cheapest Model S worth buying is the 60, and will further cement the idea that electric cars worth owning are too expensive for the average person.

[Doug_G]

At a constant speed the effects of weight will likely be negligible. Weight comes into play when you're accelerating a lot. There is a minor effect on rolling resistance.

[NotTarts]

But this is in range mode. Normal mode being 85% of range mode, I seriously doubt you'd see much more than 110 EPA miles. So if 120 EPA miles in normal mode is your fixed goal, go for the 60kWh which should go around 160 EPA miles in normal mode. Then you have a buffer for 25% degradation too and SuperCharger access.

Do you have any sources for that? I'm just curious, because it seems very odd for the EPA to change the default settings, as that wouldn't reflect real-life usage for the average consumer.

At a constant speed the effects of weight will likely be negligible. Weight comes into play when you're accelerating a lot. There is a minor effect on rolling resistance.

Not according to Tesla - they say the 40kWh model is 15% more efficient than the 85kWh model:

300 mi/85 kWh - 3.5 mi/kWh
160 mi/40 kWh - 4 mi/kWh

Here's something I posted in another forum:

What's interesting is that Tesla's estimated range doesn't decrease at the same rate as the battery pack capacity:

85kWh -> 60kWh = 29.4% decrease
300mi -> 230mi = 23.3% decrease

60kWh -> 40kWh = 33.3% decrease
230mi -> 160mi = 30.4% decrease

This indicates that Tesla thinks the car will actually get more efficient as you move down the range, probably due to a decrease in the overall weight of the vehicle. With this, though, you can make a pretty accurate estimate of what the range of the other models might be, using the EPA-tested range of the 85kWh model.

85kWh = 265 miles

So I'm guessing:

65kWh = 203 miles
40kWh = 141 miles

These values somehow come to a range difference of almost exactly 100km between each battery pack:

265mi = 426.5km
203mi = 326.7km
141mi = 226.9km

[EVNow]

I came up with the goal of 120 miles in standard mode because I drive 70 miles most days, and 90 once every other week or so (always known in advance, so range mode would be possible) I figure even with 20% battery degradation, I would be OK on range (and I could always drive a little slower, turn off HVAC, or charge in range mode to give a little extra buffer near the end of the batteries life).

Don't forget the loss of range in winter.

[Zythryn]

Are the smaller packs more efficient due to the lower power?
The 0-60 times get slower as the packs get smaller. If Tesla ramps down the power available, will that increase the efficiency?

[NotTarts]

Are the smaller packs more efficient due to the lower power?
The 0-60 times get slower as the packs get smaller. If Tesla ramps down the power available, will that increase the efficiency?

Definitely during acceleration, but even then I'm not sure if it's much of a difference because it would make, as it will still take a similar amount of energy to accelerate the car from 0-60 regardless of how quickly you do it (assuming the weight, transmission, motor, etc, remains the same).

At highway speeds, I don't think it makes a difference at all. Even if there is more energy available, the electric motor will only use as much as it needs to maintain the speed, unlike an ICE where it would be using 8 cylinders when in reality it only needs half that.