I was thinking we should have a poll for this - what do you think Tesla will offer in terms of battery sizes? Personally, I think Tesla will offer two battery sizes, around 60 kWh and 80 kWh, for something like 220 EPA miles and 290 EPA miles.

Agree on two battery sizes. But I think it will be 55 kWh and 75 kWh, for something like 230 EPA miles and 300 EPA miles. Q: What? Smaller batteries and I still guess a grater range? A: Well, if you look into this spreadsheet you will see that it is within the range of reality (Select the "Range Calculator" tab and look at the "Fictional Model 3 V1-3" columns.) (No it's not my spreadsheet)

It's certainly possible, but I'm assuming the Model 3 will be less efficient than you think. The use of steel means it won't be entirely light-weight. And the car is likely to be shorter and higher, which means more aerodynamic drag. I think Tesla will view these challenges as easier to solve with a bigger battery than to try to squeeze out every last bit of efficiency, given their Gigafactory.

55kwh and 230 EPA is completly utopic. You want the Model 3 to have a 30% smaller battery and get 10% more range than S60?

4 miles / kWh of useable battery is a good estimate. If 55 kWh is the useable capacity, we may get about 220 miles EPA. If it is the total then Tesla will struggle hitting 200 miles - which they definitely want to hit. So, I'm fairly sure Tesla will aim for 60 kWh (afterall we are talking less than $1K more in battery ?). Also, given that Leaf 2 seems to have 60 kWh battery and GM says Bolt is easily getting over 200 miles, Tesla will go for definite 200 miles from the get go - than be dependent on greater efficiencies to eek out 200 miles and fall short because of unforeseen circumstances.

Assuming that Model 3 has similar dimensions to a BMW 3-series (Model S has similar dimensions to a BMW 5-series), the rectangle area of (wheelbase * track) for Model 3 would be about 87% that of a Model S. Tesla Model S Wheelbase 116.5" * Track 66" = 7689 Hypothetical Tesla Model 3 Wheelbase 110" * Track 61" = 6710 (6710 / 7689) = 0.87. 90 kWh * 0.87 = 78.3 kWh For a smaller pack, if we assume that the 70 kWh pack could be 74 kWh with the new cells in the 90 kWh pack: 74 kWh * .87 = 64 kWh All of this is very rough guess work, but my speculation is that Model 3 will use a battery approximately 80 kWh at the top end (around 270/285 miles RWD/AWD), and approximately 65 kWh (around 230/240 miles RWD/AWD) at the lower end.

With the strong possibility the form factor results in a taller and wider battery cell something like 20700, the same rectangular area in the Model 3 would result in greater energy density.

That's a good point. I completely forgot about the cell form factor and hints from the company that they might use a more optimal cell geometry. Between that and advances in chemistry, it's difficult to estimate the ultimate battery capacity.

I remember a chart (from the recent JB Straubel presentation?) which indicated that Tesla assumes an average battery size of 70kWh for the Model 3. I selected 60 and 80, but maybe it will be 60/75 and most buyers choose 75, so the average is still 70. Hoping for 80 or more.

A 10 percent larger cell plus 5 years x 7 and a half percent greater energy density equals 50 percent more energy density per cell. now do they use less cells and save weight, or go for more range?

My guess was 60 and 85 kWh for Model 3, while Model S will get much higher capacities. Remember that the Model 3 packs will have a 40% increased volumetric energy density Source: Tesla Reimagines the Century-old Power Grid - JB Straubel | SDF2015 - YouTube

You remembered correctly! I think that chart is pretty telling. I suspect something more like 60, 75, and 90. The high end of that would allow for a jaw-dropping 300 miles of "real world" range or

I voted 60/75/90 also. Probably too optimistic, but maybe the Gigafactory will make it possible. We can always hope.

I think if model 3 will be 20% smaller than model S... the weight will be at least 20% less (at least, but maybe even less due to smaller battery pack) and the drag will be 20% less too (same Cd with lower front surface). This means than model 3 will need at least 20% less energy for the same range than model S. I bet lower cost Model 3 (35000$) will have around 50Kwh for 200 miles EPA (the model S60 gets 208 from the 60KWh pack) I also bet for higher range model 3 with a 70Kwh battery pack and a similar range to a 85/90KWh model S (20% of 85 is 68). Others improvements are also possible so the range could be even better with these battery packs.

Well if we're modelling... Will Model 3 just sit somewhere between the Roadster's 53kWh and the S's 85? The excel file for the Roadster can be found here: http://teslaflux.com/Efficiency.xls Graph from: Model S Efficiency and Range | Tesla Motors

I'm not so sure about that. Remember, they've talked about moving to more steel and less aluminum. If they were to just talk the Model S and scale it down to .80 scale (which they've said they won't), each dimension would only be scaled down to the cube root of .80, and the front surface area would be scaled down to the square of the cube root of .80, which is ~.86, so the drag would be ~14% lower. On the other hand, it's likely that the height won't be scaled down quite so much in order to leave acceptable headroom, and the length would be shortened more to make up for that. In the that case, the frontal surface area might be .88 or even .90 that of the Model S. That being said, there's also talk that the Cd will go down as far as .20; I doubt that, I think .22 is a little more likely. According to my calculations, it'd be more like 15% less energy. Elon has said over and over again that 200 miles real world range is the minimum acceptable level for an electric car, and that in order to do that you need significantly more EPA range, something like 220-250. 208 miles at 20% less energy and 5/6th battery size would be 216.7 miles, not 200. Under my estimates, a model 3 50 would get 204. Again, I don't think Tesla will release a base 3 without 200 miles real-world range, which means a bare minimum of 220 miles EPA. In my mind, that means a 60 kWh base. I definitely agree that there will be a 70 or 75, and perhaps also an 85 or 90. After all, JB Straubel did say that the third generation (3/Y) would have about 40% better volumetric efficiency than the second generation (S/X).

With three models, we need to consider what is offered across the line up. I predict the Telsa line up will select from 50, 70, 90 kW.h - i.e., M3 will offer 50 and 70 kW.h. There are economies of scale with this approach. Unless, in 2017 they have raised it 60, 80, 100 kW.h. Of course, they may stretch it - 50, 75, 100 to insure a greater mileage difference between models. Telsa, will surely have a common architecture for its batteries - the pack with be 96 cells in series as this determines the voltage at the motors, with varying numbers in parallel.

I disagree. If the Gen-III vehicles (Model 3/y/?) was the same size as as the Gen-II vehicles (Model S/X) it would make sense, but given that it will be smaller it is reasonable that the battery from Gen-II will not fit in the Gen-III. So it will be one type of battery for the Gen-II - 70 and 90 (I think 85 will disappear soon), and one type of battery for the Gen-III. Maybe 55 and 70? But this Gen-III 70kWh battery will not be the same 70kWh battery as the Gen-II 70kWh, so no "economies of scale" here.