More anti-ev gibberish

[Zzzz...]

Sorry, I didn't mean to nitpick, I just wondered about the energy density. Do we know the weight of the 85 kWh pack?

I haven't heard of any specific weight of pack mentioned anywhere. But cells themselves universally believed to have 245Wh/kg specific energy, and there are about 7000 of them each weighting 43g or so...

But in 10k filing Tesla mentioned they have several cells suppliers and two of them fully qualified. Cells from different producers could have slightly different characteristics, and some cars rolling off assembly line probably have got non Panasonic cells...

 

[JRP3]

I was going to calculate using the difference between the 60 and 85kWh cars, but I think the weight difference is only about 190lbs, which for 25kWh works out to about 290Wh/kg, higher than individual cell density, so they must have added something to the 60's that kept the weight closer to that of the 85's.

 

[Norbert]

Yeah that was the promise. IIRC they never came through on the promise of free electricity, because transmission over distance always costs something to provide.

Just to be clear, I'm not promising free electricity (and never expected nukes to be a "final" solution). However I do see the possibility that generation of energy will cease to be a major environmental concern (it sort of has to, because fossils and most other resources are too limited). Potable water consumption will be a major concern.

 

[Norbert]

Reminds me of the 50's sales pitch for Nukes.

If you are referring to just the way I expressed it, then point taken.

 

[stopcrazypp]

You quoted the Roadster pack density at 124 Wh/kg, which used 2.2 ah cells, the S uses 3.2 ah cells, I highly doubt the pack density only improved to 135 Wh/kg with the new cells. Also as I noted the non cell materials are likely lower energy input materials since they don't need to be high purity or need to be assembled under clean room conditions.

We don't have enough data to figure out the Model S pack density (the weight difference approach with the 60kWh, 85kWh packs might get you close, but as you pointed out, there's some iffy things with the weight that Tesla did to the 60kWh pack).

But we do have enough data to figure out the pack density of a Roadster pack if you swapped out all the cells for newer Model S cells.

Some facts first:
-121Wh/kg for Roadster pack
http://www.teslamotors.com/roadster/technology/battery
-Roadster used 2400mAh cells
http://www.teslamotorsclub.com/showthread.php/3810-Roadster-battery-(ESS)/page2
-Model S used 3100mAh cells
http://www.engadget.com/2010/04/23/panasonics-3-1ah-batteries-to-be-used-in-the-tesla-model-s-hav/

Approach 1 (cell/pack approach):
Roadster pack has 6831 cells, weighs 463kg (56kWh, 121Wh/kg), with 92% utilization of cells (calculated 2215mAh used out of 2400mAh, number also matches well with blog post below saying cells limited from ~2-95%SOC)
http://www.teslamotors.com/blog/bit-about-batteries
If you swapped all the cells to Model S cells you get 70.1kWh (3.6V * 3.1Ah * 6831 cells * 92% use) with a pack density of 151Wh/kg.

Approach 2 (density approach):
121Wh/kg for pack
195Wh/kg for 2400mAh cells (3.7V, 2400mAh, 45.5g Sanyo cells I found on Ebay)
245Wh/kg for 3100mAh cells (3.6V, 3100mAh, 45.5g Panasonic NCR18650A)
If you assume the weight ratio between the cell and overall pack remains the same after you swap the cells, you get 152Wh/kg (121*245/195).

 

[Norbert]

If you assume the weight ratio between the cell and overall pack remains the same after you swap the cells, you get 152Wh/kg (121*245/195).

Great idea to calculate it using Roadster values. And this number still includes a likely heavier battery management system, than the one the referenced study used for its numbers (for a 75 Wh/kg pack). This means an even smaller part is energy-intensive in production, and so the resulting energy needed is less than half of JP's number, for 'a Tesla battery pack'. Aside from other factors being wrong as well, in JP's article.

 

[vfx]

Checking a Skeptic’s Fuzzy Math

Bjorn Lomborg’s recent opinion piece in the Wall Street Journal, “Green Cars Have a Dirty Little Secret,” argues that the environmental benefits of grid-connected vehicles do not justify federal investment. The author is mistaken on both the benefits to the environment and the benefits to the taxpayer.

Checking a Skeptic’s Fuzzy Math

 

[JRP3]

If you swapped all the cells to Model S cells you get 70.1kWh (3.6V * 3.1Ah * 6831 cells * 92% use) with a pack density of 151Wh/kg.
.....
If you assume the weight ratio between the cell and overall pack remains the same after you swap the cells, you get 152Wh/kg (121*245/195).

Nice work.

 

[eledille]

But we do have enough data to figure out the pack density of a Roadster pack if you swapped out all the cells for newer Model S cells.

Yes, nice work. So what remains is guesstimating the difference between the Roadster pack format and the Model S format.

The Roadster pack is more compact. That means higher volume to surface area ratio, which means less packaging per cell. I also think Tesla has reserved more of the capacity for safety - there is no range mode charge anymore and it seems the car shuts off earlier to avoid any possibility of bricking.

The Roadster pack contains 311 kg of cells. 463 kg - 311 kg = 152 kg of packaging, wiring etc. Assume half of that is the enclosure and the rest is coolant, wiring etc. Say the Roadster enclosure weighs 75 kg and that the Model S variant is twice as heavy. There are slightly more cells in it, so maybe non-cell, non-enclosure pack components weigh 85 kg - that would be 235 kg total.

85 kWh requires 85000/(3.6*3.1) = 7617 cells. There is some reserved capacity, so assume 8000 cells, weighing 364 kg. The total would be 599 kg, for a power density of 142 kWh/kg.

I think somewhere around 140 Wh/kg seems likely. That's pretty good.

 

[Norbert]

The Roadster pack is more compact. That means higher volume to surface area ratio, which means less packaging per cell. I also think Tesla has reserved more of the capacity for safety - there is no range mode charge anymore and it seems the car shuts off earlier to avoid any possibility of bricking.

I think somewhere around 135 Wh/kg seems likely.

The size of the safety reserve shouldn't affect theses calculations. I don't know if the Model S has more packaging than the Roadster in terms of weight, yet even if that is the case, then this would make the number (likely) less comparable to the 75 Wh/kg number. Any additional packaging would most likely not be very energy-intensive, so actually better ignored here in this calculation.

Meaning, the number to use for comparison would still be 150 Wh/kg, or likely *even higher*, as even the Roadster is likely to contain more packing than the battery pack with the 75 Wh/kg number (which was used in the study).

After all, we are not trying to calculate the battery pack's weight, but the energy required to produce it, which in my understanding is (mostly) determined by the battery cells themselves.

 

[Robert.Boston]

I do see the possibility that generation of energy will cease to be a major environmental concern (it sort of has to, because fossils and most other resources are too limited). Potable water consumption will be a major concern.

In a world with unlimited supplies of cheap, sustainable energy, we also have unlimited supplies of cheap, potable water. Desalination isn't particularly difficult; it's just energy-intensive.

 

[JRP3]

I also think Tesla has reserved more of the capacity for safety - there is no range mode charge anymore and it seems the car shuts off earlier to avoid any possibility of bricking.

Who told you that, John Broder?

 

[GSP]

While the Model S still has range mode charging, it doesn't have extra range held in reserve when driving that can be activated by switching to range mode like the Roadster has. This is probably causing some confusion.

GSP

 

[JRP3]

I see. In any case it's not relevant to the finished pack kWh/kg number used for calculating construction energy use.

 

[brianman]

While the Model S still has range mode charging, it doesn't have extra range held in reserve when driving that can be activated by switching to range mode like the Roadster has. This is probably causing some confusion.
GSP

Ok, now you have me confused.

I thought the underlined was range driving moe not range charging mode on the Roadster. Or are both considered simple range mode? Perhaps I need to update my understanding / terminology.

Anyway, I think the assertion is still off. Model S has range charging mode, range driving mode, and has reserve beyond the "0 miles" UI. What's "missing" is a setting to turn off the "drive beyond 0 miles in the UI". I'd be surprised if anyone on the planet would ask for this feature. As such, the notion that Model S is "missing something" here seems off to me.

That said, there's plenty to improve or add in the Model S offering. I just don't think the comparison of Roadster and S feature set here was on the mark.

 

[eledille]

I see. In any case it's not relevant to the finished pack kWh/kg number used for calculating construction energy use.

If more energy is inacessible, then that will impact the Wh/kg number for the finished pack compared to the cells and also the construction energy use vs finished pack kWh.

Model S has range charging mode, range driving mode, and has reserve beyond the "0 miles" UI. What's "missing" is a setting to turn off the "drive beyond 0 miles in the UI". I'd be surprised if anyone on the planet would ask for this feature.

Ok, I thought range charging mode was gone and Model S only had range driving mode. My mistake, sorry. I certainly don't want the "drive beyond 0" feature back.

 

[JRP3]

All cars reserve some of the pack capacity, that doesn't affect the kWh rating of the pack or how much energy would be used to build that pack.

 

[stopcrazypp]

All cars reserve some of the pack capacity, that doesn't affect the kWh rating of the pack or how much energy would be used to build that pack.

I think there is confusion in the "reserve" terminology used.

What you are saying is that the battery pack Wh/kg throughout this thread refers to the advertised kWh rating of the pack (40/60/85kWh for Model S, 56kWh for Roadster), so it's irrelevant how much of that is used as "reserve" when driving beyond "0 miles".

What IS relevant is the smaller voltage window of the cells, which I mentioned for the Roadster is ~2-95%SOC or 3V-4.15V (vs 2.5V-4.2V for a fully utilized 18650). Don't know what the numbers are for the Model S, but it's possible to figure it out if anyone has the "fully charged" battery voltage (should be 398.4V if 4.15V per cell) and the battery voltage when the car won't move anymore (288V if 3V per cell).
http://www.teslamotors.com/blog/bit-about-batteries

What this voltage window means is that the "85kWh" pack may contain 91kWh worth of cells since Tesla isn't using the cells from 0-100%SOC and I think that is what eledille is talking about.

 

[Kaivball]

But at the end of the day, if someone asks you about this, is to keep some perspective. The first ICE cars were horribly inefficient. They got terrible mileage and spewed tons of exhaust. Now after over a century of R&D they are where they are today. EVs and battery tech is still growing. Just like it was foolish to look at an ICE car in 1895 and think they were going to stay that way forever it is foolish to think EV and battery tech will stand still as well.

The other problem I see some people do (haven't read this article so don't know) is that they compare a Model S to a Ford Focus or other econobox that gets "good mileage" when Model S' competition is the A7, 5-series, etc.

Except that the first battery car ran 100 years ago...

Early electric cars traveled more than 50 miles on a charge...

They've been at it for 100 years. Just like we've been at solar panels for 40 years...
It's not new technology at all. The advance,nets are just much, much slower.

 

[Norbert]

It's not the number of years. It's more the amount of money in situations where a competitive advantage is recognized to depend on technical progress.

That amount is increasing for both both solar and batteries, and both are making large steps forward in recent history.