Model 3 to start at 60kWh

[JeffK]

Thought experiment:

A new battery chemistry yields 10 watt/hours per gram.

You use 1Kg of this battery material and roll it in to 18650's to make pack A

You also use 1Kg of this material and roll in in to fewer 2170's to make pack B.

Q1: What is the energy capacity of each pack?

Q2: How far could a car that uses 250kWh/mi travel on either pack, all else being equal?

Q1 : same energy capacity, different energy density. Keep in mind Pack A weighs more than Pack B and takes up more volume. This is why there are two different measurements for cell energy density and pack energy density.

Q2 : question doesn't make sense, Car with Pack B uses less energy per mile so all things are not equal.

 

[stopcrazypp]

Neither of which:

A) Has necessarily to do with format size

B) Changes the efficiency of the car and thus it's power requirement

Well I'm not really arguing the format size (although if you assume the same cell wall thickness and material, the 2170 does have better energy density than the 18650; you can do the math on cylinder surface area vs volume to verify this is the case).

I'm talking about the claim the efficiency number is independent of IR. At least for the purposes of this context (the EPA efficiency) that's not true. It may be true however of the displayed efficiency on the dash.

The key point is what does the "Wh" measure in the Wh/mi figure.
On the dash display = discharge "Wh". For this, IR doesn't matter.
For EPA MPGe testing = charge AC "Wh". For this, IR definitely matters.
For EPA range comparisons = nominal pack "Wh" or charge DC "Wh". For this, IR definitely matters.

I'll give an example. Say you have a pack size that is 60 kWh usable nominal. A low IR pack might be able to get 59 kWh discharge, a high IR pack maybe 57 kWh discharge on EPA cycle (numbers for illustrative purposes only). In both cases, the car's dash display Wh/mi consumption on EPA cycle is 240 Wh/mi (because everything else other than the pack IR is the same).

The low IR pack gets rated at 246 miles of EPA range.
The high IR pack gets rated at 238 miles of EPA range.

 

[scaesare]

Five gallons of water might weigh more with five 1 gallon jugs due to the containers themselves. In addition, five 1 gallon jugs will also take up more volume for 5 gallons and thus be less dense.

Does that make sense? Besides chemistry, which we know is going to be different, the cell format does matter.

I don't know how many times I have to point out that weight was already considered separately in the post I was referring to.

Allow me to quote it again:

...4mi/kWh isn't too far fetched. 2170 cells, lighter weight, better drag coefficient......

 

[ModelNforNerd]

Can we all agree that the specifics in question here are the 18650s and the 2170s. So to tell us what happens in every other comparative situation between 2 battery formats is irrelevant. Tesla doesn't use anything except these 2.

So....without pulling out slide rules and telling you I have a degree in chemical engineering from Hooters....the simple fact that a 60kWh pack of 2170s will take a Model 3 60 further than a pack of 18650s will take a Model S is indeed true. That is due to the size difference in vehicles AND packs.

To truly get a real world answer, we have to wait until Tesla's 18650 contract expires with Panasonic (end of 2017, I believe).

Then you will have a "legacy" lineup of Model S to measure up against the newer Models sporting 2170s.

They're going to go further and charge faster than their legacy Tesla counterparts. And that's what matters, because that's what we're comparing here.

 

[scaesare]

Q1 : same energy capacity, different energy density.

10KwH of energy made from 1Kg of material in each pack. Why is the energy density different?

Keep in mind Pack A weighs more than Pack B and takes up more volume.

Why?

Q2 : question doesn't make sense, Car with Pack B uses less energy per mile so all things are not equal.

Both packs go in to the same car. The only difference is the cell sizes the packs are made up of.[/quote][/QUOTE]

 

[JeffK]

10KwH of energy made from 1Kg of material in each pack. Why is the energy density different?

Why?


Both packs go in to the same car. The only difference is the cell sizes the packs are made up of.

Think about the water jugs and it will come to you. This is a common error in science courses too, people forget to weigh the container.

As previously stated by yourself and others, the Model 3 is lighter in addition to the use of 2170s. Lighter car and lighter battery pack.

 

[ModelNforNerd]

I don't know how many times I have to point out that weight was already considered separately in the post I was referring to.

Allow me to quote it again:

since you're so fixated on one grammatical point, you're missing the larger point being made....allow me to clarify.

The Model 3 is ~85% the size of the Model S, with simpler wiring, and a different chassis. So in that sense, it will be a lighter VEHICLE.

ALSO...the 2170 pack will be lighter than its nominal 18650 counterpart.

But since you have to put the vehicle AND its pack onto a scale to get your GVW, I chose to refer to the vehicle's weight in the singular sense, not realizing someone would go Zapruder Film semantics on us all to basically argue what we've all been saying, but slanted through the lens of 2 words being taken in a separate context.

 

[scaesare]

Well I'm not really arguing the format size (although if you assume the same cell wall thickness and material, the 2170 does have better energy density than the 18650; you can do the math on cylinder surface area vs volume to verify this is the case).

I'm talking about the claim the efficiency number is independent of IR. At least for the purposes of this context (the EPA efficiency) that's not true. It may be true however of the displayed efficiency on the dash.

The key point is what does the "Wh" measure in the Wh/mi figure.
On the dash display = discharge "Wh". For this, IR doesn't matter.
For EPA MPGe testing = charge AC "Wh". For this, IR definitely matters.
For EPA range comparisons = nominal pack "Wh" or charge DC "Wh". For this, IR definitely matters.

I'll give an example. Say you have a pack size that is 60 kWh usable nominal. A low IR pack might be able to get 59 kWh discharge, a high IR pack maybe 57 kWh discharge on EPA cycle (numbers for illustrative purposes only). In both cases, the car's dash display Wh/mi consumption on EPA cycle is 240 Wh/mi (because everything else other than the pack IR is the same).

The low IR pack gets rated at 246 miles of EPA range.
The high IR pack gets rated at 238 miles of EPA range.

Certainly I'm not suggesting IR, doesn't have an effect. Even with the same pack, if you pull energy out of at a rate of 1amp you will get a different overall energy output than if you pull at a 1,000A rate. Certainly losses are real.

But in the context of this discussion (at least the posts I'm replying to), the issues are the efficiency of a the Model 3 (vs. the Model S), and what is a reasonable Wh/mi usage. Factors for that are aero, rolling resistance, mass, drivetrain losses, etc...

Thus if the Model 3 is capable of getting by on 240 Wh/mi, then that's what it will draw. If an 18650 pack has an IR that's bad, you won't get as much range. If it has a 2170 pack with poor IT, it also won't get as much range. The same would go for a Model S.

The overall energy density has primarily to do with cell chemistry, anode/cathode design, etc...

You can have an 18650 with low or high IR. You can have a 2170 with low or high IR. You could have a have an 18650 with 100Wh/Kg energy density. You could have a 2170 with 100Wh/Kg energy density.

You can use different cell wall materials and thicknesses. You can terminate either cell on one end only, or both. You can use wrappers or forego them. All of these things affect overall cell weight, and it doesn't necessarily have to do with format size.

 

[JeffK]

You can use different cell wall materials and thicknesses. You can terminate either cell on one end only, or both. You can use wrappers or forego them. All of these things affect overall cell weight, and it doesn't necessarily have to do with format size.

Very true, luckily, in this case, we know the 2170s are more density by both format and chemistry according to JB. I hope this means we'll be in good shape with Model 3.

 

[ModelNforNerd]

remember: the inverter will be "close" to the Model S as well.

Tesla Model 3 exclusive leaked specs: 300kW+ inverter architecture putting its power capacity near Model S

 

[JRP3]

All of these things affect overall cell weight, and it doesn't necessarily have to do with format size.

Using the same chemistry in a 18650 cell and 2170 cell means the specific energy of the 2170 cell should be higher for two reasons. First the 2170 has a higher ratio of active material to external casing. Second, each cell is wound around a mandrel, which when removed leaves an empty space filled with electrolyte but no electrode layers. Assuming the same diameter mandrel is used the 2170 will also have a higher ratio of active material to empty mandrel space. At the pack level having fewer overall empty mandrel spaces by using fewer of the larger 2170's should add up to something significant.

 

[Jeff N]

Elon also said the Model 3 would get 200 miles in the real world. The Bolt does not have as good aerodynamics, but it only gets 190 miles at 70mph (with AC on). It has a battery that is larger than 60kWh.

So I would not assume that this necessarily had anything to do with the Bolt. It may simply be trying to meet those requirements.

The actual Car & Driver claim was 190 miles at 75 mph (not 70).

Chevrolet Bolt EV - Car and Driver

However, the quadratic effects of aerodynamic drag mean that the faster you drive, the faster the battery drains. So in our most recent rendezvous with the Bolt, we performed a real-world range test that mimics a long highway road trip. With the cruise control set to 75 mph and the climate system set to 72 degrees, we drove the battery to exhaustion in 190 miles.

 

[ModelNforNerd]

The actual Car & Driver claim was 190 miles at 75 mph (not 70).

Chevrolet Bolt EV - Car and Driver

Here in the Northeast, that is a solid, real-world-relatable stat. No one actually does ONLY 65 on the highway in the summer up here. That is pretty significant when you realize it will take you much longer than 20 minutes to replace those electrons on a road trip. Bolt buyers better do their homework.

 

[Jeff N]

Here in the Northeast, that is a solid, real-world-relatable stat. No one actually does ONLY 65 on the highway in the summer up here. That is pretty significant when you realize it will take you much longer than 20 minutes to replace those electrons on a road trip. Bolt buyers better do their homework.

Of course, it would take a typical Tesla, say an S85, much longer than 20 minutes to restore 190 miles of range also. This video from Bjorn shows it taking 52 minutes to add 190 miles (adding 306 km to the existing 30 km at start of charge).

 

[ModelNforNerd]

Of course, it would take a typical Tesla, say an S85, much longer than 20 minutes to restore 190 miles of range also. This video from Bjorn shows it taking 52 minutes to add 190 miles (adding 304 km to the existing 30 km at start of charge).

fair enough. it wouldn't be measured in hours. and with the new cells, it may even be less time than 52 minutes

 

[bro1999]

The actual Car & Driver claim was 190 miles at 75 mph (not 70).

Chevrolet Bolt EV - Car and Driver

And GM stated that WOT @93 MPH (no climate, flat roads), the Bolt could go 160 miles on a full charge.

I just completed a 165 R/T trip on Monday in my Bolt (with 4 people) averaging 65 mph on the highway (95% of the drive was highway). Overall economy was 4.2 miles/kWh, which would project to around 250 miles of highway range on a full charge. Official EPA highway range rating is 217, I believe. The aero-brick Bolt not quite the "disaster" everyone thinks it is.

 

[ModelNforNerd]

And GM stated that WOT @93 MPH (no climate, flat roads), the Bolt could go 160 miles on a full charge.

I just completed a 165 R/T trip on Monday in my Bolt (with 4 people) averaging 65 mph on the highway (95% of the drive was highway). Overall economy was 4.2 miles/kWh, which would project to around 250 miles of highway range on a full charge. Official EPA highway range rating is 217, I believe. The aero-brick Bolt not quite the "disaster" everyone thinks it is.
View attachment 229094

Is......



is......there a......

Bolt blog that maybe you meant to be on?


Are you one of the "real people" from those terrible Chevy commercials?

 

[Jeff N]

And GM stated that WOT @93 MPH (no climate, flat roads), the Bolt could go 160 miles on a full charge.

I believe that was reportedly stated by a GM engineer at a Bolt media briefing (actually it was stated as 170 miles, I think) but the reported claim was later retracted/disputed by GM's press rep so it's an unreliable claim.

It's also an implausibly high number of miles, I think, although it would be interesting for someone to try it on a race track somewhere.

 

[stopcrazypp]

The actual Car & Driver claim was 190 miles at 75 mph (not 70).

Chevrolet Bolt EV - Car and Driver

Yes, I misremembered the C&D, but same thing, Model 3 will have to hit over 200 in roughly the same speeds (which was intended to simulate real world).

 

[206er]

this battery news is great! battery size was going to be our biggest and maybe only upgrade, but now we can consider other upgrades!