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How much will the 40 kWh Model S weigh?

I have been driving a 23 kWh Ford Focus for the past few weeks and have decided that the 40kWh Model S will be the way I go when it's time to confirm my car. The 60 kWh would be nice, but I'm not convinced that car would make sense for me at double the price of the Ford. Plus I was able to lease the Ford, so if after three years the car is outdated or having issues I'll be able to walk away. The Model S is more of a commitment.

I'll add that the Ford is a nice car and I wish Tesla was going to build something comparable instead of the Model X as their follow on to the S. One of the big reasons I chose the Focus over the current Tesla offerings is that it is more than 1000 lb. lighter.

From the Specs Page: Curb weight: 4,647.3 lbs

@Jagbert - one of the reasons Tesla is waiting to do the mass-market car (aside from bootstrapping the company by starting with a niche market, moving to a bit larger market next, etc) is the battery technology needs to improve.

I think Tesla wants to be able to offer a 300mi version of the GenIII, but you can't do that if it adds $20k over a ~$30k base model. In three of years, assuming 8% improvement in price/performance, that gets the price down to $15k extra for the big battery. Maybe you can use a bit s couplemaller battery since the car will be smaller and lighter, but it is still going to be expensive.

4,647.3 lbs is the 40kWh? I guess the spec sheet is clear but I thought it might be a little less than that.

4,647.3 lbs is 85kWh I think... 60kWh and 40kWh is lighter, but I've never seen this numbers :(

Where did you hear that? I think its in the blog section somewhere, I remember reading that 40KWh and 60KWh are comparable (if not identical) in size and weight to an 85KWh. The Battery cells have form factor and weight, just that they are rated for lower capacities. Rest of the structural frame, motor, etc should be same for all 3 models, no?

The "SPECS" page on this site lists the 40KWh is says weight is 4,647.3

I would be extrremely surprised if the smaller sized battery cars weigh the same as the 85 KWH car. Everything I've read so far says that the smaller battery packs weigh less. I also find it hard to believe that Tesla would use a lower rated capacity cells in the smaller battery cars.

There have actually been several statements that they weigh the same, so prepare to be extremely surprised at fact you find hard to believe.

The main reason Tesla would use the lower capacity batteries is cost. They are a lot less expensive. The added benefit is in testing. If the car is structurally the same, the testing data already applies and no further crash testing would be necessary. The assembly line mechanics dont have to be changed either except for the ratings of the parts. It is like changing a light bulb. The bulb changer doesn't care if it is a 60W or a 90W as long as they are the same physical dimension.

I was told by the Chicago Oak Brook sales location that the 40kw will weigh 200-300 lbs. less than the 85. Entirely due to weight of the battery.

Quotes are from this page...

http://www.teslamotors.com/models/specs

"40 kWh microprocessor controlled, lithium-ion battery"
"Curb weight: 4,647.3 lbs"

djp@pixi.com the specs page is not the Bible. I also have been told by Tesla Palo Alto that there will be a weight reduction with the 40kWh.

4,647.3 lbs is definitely 85kWh. Could be that 40kWh version has same weight, but I don't believe that is the case.

AFAIK all versions do actually use same battery type (Panasonic NCR18650a 3.1Ah battery) even that when those different battery types were introduced there was a lot of speculation that smaller battery packs use different cell types.

All speculation of course at this point, but here's what logic suggests:

The 40kWh will indeed be several hundred lbs lighter.

The reason: although the older cells are somewhat cheaper, it likely saves about as much money to reduce the electrical interconnect support for the extra cells, and surf the economies of scale from aggregate volume in a single cell type.

I was chatting with JB at one event and my take from the conversation was that the cells are very consistent, with very low defect rate, so it is very beneficial to standardize on that one cell type for their entire line.

I also have a hard time believing that Elon, JB, and the whole A-team of engineers would ever allow dead "ballast" weight in their elegantly optimized design.

My betting is that it will be the same cell, and under 4,000 of them instead of 8,000. The pack casing will likely be common to both, but lightweight inserts will dam-off half the internal volume so that they can save half the coolant mass as well. (And shed lots of copper interconnect mass too).

The reduced weight will help offset some of the very significant horsepower loss, allowing it to still turn in a respectable 6.5 sec 0-60 time.

Further evidence of this surmise: look at the range vs. Wh quotients. 160/300 >> 40/85. The smaller pack delivers more miles per watt hour, which strongly points to reduced mass.

The 40 kWh car is a terrific value, if your lifestyle can live with the reduced range.

I guess we'll find out this Spring.

Handling should be somewhat different too, and not all better, paradoxically.

While lower mass definitely helps with agility, the Cg will actually shift upwards (reflecting less influence of the super low height battery mass), so body roll may increase.

Ride will also likely not be quite as luxurious. The ideally placed, massive 85 kWh pack acts as a formidable intertial damper to soak up chassis vibration.

I'm sure the 40 will still drive great, but despite the common sense benefit of reduced mass, the 85 will likely still be the more sumptuous ride.

Will be interesting to compare track performance when the 40 comes out.

Mass is enemy of performance. With less mass 40kWh should be able to turn much sharper than 85kWh version even that power to mass ratio is in favor of 85kWh version. 85kWh probably feels smoother though.

@Timo - the 85kWh battery uses 3.1Ah cells, but the 60/40 use 2.2Ah cells. So, I would expect the 60kWh to weigh exactly the same as the 85kWh (if you have the supercharger hardware) and the 40kWh to be lighter.

Where did you find that info? I have seen gazillion speculations about the battery chemistries (and made my own speculations as well), but nothing concrete from Tesla.

It is possible that 40kWh can't have supercharger just because lower number of cells, and 60kWh does have enough cells to make it possible, so that supports your writing.

I've heard the same reports since last year, but never any clear representation from TM as to the actual config.

I'm sticking with my speculation, based on logic.

When all is said and done, I bet we find that there's just one cell type, with different cell counts in the different packs.

BTW, I think there is no technical barrier to supercharging a small pack. Rather, the problem is market positioning and pricing. It's not a practical combo. It's a tough sell to try to make it all rhe way from one sc to another on a 40 pack.

The 40 is a great city car that hits a good price point. If you want to do any serious road-tripping, get a bigger pack.

I was told by a Tesla sales rep that they put weights in the smaller battery packs to make them weigh the same. He said that this meant that they wouldn't have to crash test the smaller battery cars separately. Plausible I guess....

Plausible, but sounds really weird. Battery alone isn't really that heavy that 2/3 of the cells gone would seriously change the car behavior, it should pass the test with almost exactly same result as 85kWh version.

8000cells * 46g = 368kg * 2/3 = 245kg difference 123kg, that's less than two passengers worth. Even if we count quite a bit more from cabling and make that 46 to say 55g it still is just 440kg - 293kg = 147kg, which is only about 7% of the car total weight.

Battery pack is structural part of the car though, so it would need to keep same structural strength with less batteries in order to behave similar fashion in crash test, so if the battery cells themselves play a role there, maybe that's what they need to replace and this is then explained to sales persons as "added weight".

It's all marketing. If you spend 100k on an 85kwh car you don't want to believe that someone spening 50k is getting anything that might improve performance over your car. Thus Tesla is reluctant to give this information to the public. Seriously they know exactly how much less the 40kwhr car weighs but they aren't making this public. This fact alone tells you they are managing the information flow for some purpose. Does anyone really believe they don't know??

The 40kwh should weight less. If it doesn't it's because they intentionally added weight. I doubt the weight added is done for handling or crash testing purposes. A lighter car should be safer in a crash and this amount of weight wouldn't affect handling much at all.Even if it did it's easy to adjust shocks.

Interesting question. If we assume that the weight of the car has no significant impact on the efficiency at constant high speed (since that is dominated by aerodynamics), but at low speed the mass comes into play linearly in rolling resistance and acceleration losses. Then the difference in efficiency must be less than the difference in mass for the EPA mileage test (which includes both lows speed and high speed components).

EPA for the 85 is 265
EPA for the 60 is 208
Mass of 85 kWh car (M_85) = 4650lb

so M_60 < M_85*(265*60)/(208*85) = 4180lb
A difference of 470 lb.
So it looks like the 60 must be at least 470 lb lighter than the 85.
By extrapolation I'd expect the 40 to be at least 750lb lighter than the 85.

PS, when its fully fueled the 85 weighs about 3.4ng heavier, vs 2.4ng for the 60. You may want to take this into account :-)

Or not. ;) Those electrons don't get "burned" and exhausted, btw. They just relocate within the battery, after a detour.

mass = energy according to relativity, just as hot objects have greater mass than they do when they are cold (and he did say "ng": nanograms"). So I reckon he is correct.

They didn't go anywhere much, just shifted around the battery. So all the ng are still in the car!

Nope, the electrons move to different bound states, with ~4eV higher energy per electron when charged. A simplistic (ie not entirely correct way) to think about this is that the higher energy electron states the electrons are moving faster, and therefore gain mass proportional to their change in gamma (1/sqrt(1-v^2/c^2)).


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