Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

[AWDtsla]

That doesn't sound right. Sure a larger volume to surface area ratio would limit performance at high C rates, but likely not with regular and low loads? And as has been much discussed in this thread aren't we assuming that nameplate capacity is measured under favorable conditions i.e. no high temperatures and slow discharge?

Also having heard Elon and JB saying they're not married to 18x650 makes me think this isn't some particular sweet spot dimension.

Elon has said publicly the large prismatic cells are very difficult to cool/manage. While 18650 might not be set in stone, small cells do seem like they are.

Seems like it would be simpler to build a cooling jacket for flat cells though, however only 1-2 layers thick, not the bricks everyone else uses.

 

[JRP3]

Interestingly, a 20mmx70mm cell has ~33% more volume than a 18mmx65mm cell. Yet the rating on that cell would seem less than 33% more than the the 18650's that Panasonic currently sells.

It's not likely a strict function of volume, but the capacity limits may be thermally constrained by the surface area from which heat can radiate--the surface area increased about 20% and the capacity increased 21%.

C rates might be constrained by surface area but capacity should not. As I pointed out after flathill posted that, the specific energy of that cell looks a bit worse than what Tesla is currently using, or was using in the 60's and 85's, and most certainly the new 90's.

Elon has said publicly the large prismatic cells are very difficult to cool/manage. While 18650 might not be set in stone, small cells do seem like they are.

Seems like it would be simpler to build a cooling jacket for flat cells though, however only 1-2 layers thick, not the bricks everyone else uses.

I think the new Bolt pack only has a cooling plate on the bottom of the cells, which if it works is much easier than cooling passages between individual cells, be they prismatic or cylindrical. Presumably they can get away with that because of the less volatile nature of the NMC chemistry they are using.

 

[flathillll]

the two ends of a 18650 cell are 12X more conductive than the side (think direct-er connection to jelly roll)

if you heat/cool on only one end thru a base plate (with terminals on the other) only you are still doing 6X better than a full cooling jacket wrap around the entire circumference of the cell. Right now the current model s pack does not even come close to a full wrap with the wave tubes.

note with the current 18650 cell the temp spread of a cell cooled with a wrap is 1C (core is 1C hotter)

note with the gigafactory format cell the temp spread of a cell cooled with a wrap is 2C which is acceptable

note with the gigafactory format cell the temp spread of a cell cooled one one end is somewhat acceptable

note with the gigafactory format cell the temp spread of a cell cooled one both ends is acceptable (think bus "bar"

note with the LG Bolt form factor cell I would estimate the temp spread is closer to 30-40C under load (based on similar prismatic cell modeling)

note some Ford Focus EV's (which also uses liquid cooled prismatic cells) show a 20+% decline in range after ~1 year

come to the Bay Area and you can meet ex Tesla engineers at Alta Motors (BRD), Zero Motorcycles, Lightning Motorcycles, Joby, Mission Motorcycles (Apple killed the "mission" by offering 250k signing bonuses and tripling pay so now almost the whole mission team work on the iCar)

 

[Auzie]

...................

come to the Bay Area and you can meet ex Tesla engineers at Alta Motors (BRD), Zero Motorcycles, Lightning Motorcycles, Joby, Mission Motorcycles (Apple killed the "mission" by offering 250k signing bonuses and tripling pay so now almost the whole mission team work on the iCar)

Damn Apple

..... Tesla is a labor of love.....

Moving people from labour of love to money labour

I can sense some poetic justice in the future

 

[lolachampcar]

Apple may have provided a soft landing for Mission personnel but that is not why Mission went away. At least I saw the writing on the wall soon enough to get (most) of my deposit back.

 

[flathillll]

nope Apple destroyed Mission. They lost one team member to Apple which didn't appear to be a big deal at first, but just as they were about to lock in funding to ramp production Apple poached the rest of the core team. The trick was the first person they recruited knew everyone's salary at Mission...valuable information to the poacher(apple)... Investors then pulled out and the rest is history. Even if you believe in the "mission" it is hard to turn down a huge signing bonus and salary increase. Apple is not rotten to the core but they do play to win

Funny thing is all the ex mission employees are now working as slaves on "ipad development" or other such nonsense. apple doesn't care about iCar secrecy per se. they just want to make it harder to poach their iCar team (herd of slaves). very smart. the mission bike with the integrated "combo" controller(inverter)/charger was a masterpiece and it didn't work like AC Propulsion tech which needs to use a motor wind

 

[sorka]

This is probably the thing to hide behind. The car still makes its EPA ranges (weather permitting of course, don't get me started). Just like the 691/762hp debacle where the car was still hiring it's 0-60 times even though the HP was basically a made up number.

I'm very late to the party and don't have time to read through all 51 pages. Wk needs to stop creating threads that go on and on forever. Darn him

My P85D makes the EPA rated range that was advertised so it's a lot harder for me to have a beef with this issue than the 691 hp issue. 0-60 times was never my beef. It was the 70-90 passing speeds of 3 seconds with 463 hp that would have been closer to 2.1 seconds had it actually made 691 hp. But was untestable due to speed limiting the test drive vehicles to 80 MPH.

But in this case, I'm getting the range performance I was sold.

Where it gets a little sticky are my expectations that had the battery really been 85 KWh that as degradation occurred, the software could open up the hidden capacity to hide the degradation for a while. We all knew that only 76 KWh was the usable capacity before the mythical, now obviously non existent, zero mile buffer kicked in.

Now there's only 4 KWh to play with and the 17 miles that someone drove after hitting 0 was obviously a calibration issue.

But still, that doesn't translate to damages as the range performance is there and the degradation is small over 100K miles, then it's fine.

That said, if this gets out and other REAL 85KWh competitors result in lower resale value of our cars because of this, then that's another example where there could be damages.

So I have mixed feelings about this. They should only advertise the usable capacity i.e. it should have been the P76D. But failing that, they certainly shouldn't advertise more physical capacity than the pack actually has i.e P81D.

Any revelations from pages 7 to 51 that I should know about? Any super critical posts to this thread that someone remembers and can throw a link in here?

 

[kennybobby]

Are you talking theoretical or actual number of cells here?

Actual cells:

85 = 7104 (96s74p)

70 = 6216 (84s74p)

60 = 5376 (84s64p)

 

[pupik]

Are you talking theoretical or actual number of cells here?

Actual cells:

85 = 7104 (96s74p)

70 = 6216 (84s74p)

60 = 5376 (84s64p)

****! :cursing: my source was here :biggrin::biggrin::biggrin:
SORRY... :redface:

 

[scaesare]

It's not likely a strict function of volume, but the capacity limits may be thermally constrained by the surface area from which heat can radiate--the surface area increased about 20% and the capacity increased 21%.

What's odd is that I recall some talks/videos from either JB, Elon or both (I honestly cant remember the specifics) seemed to indicate that, although they used the 18650 as a result of the already-established economies of scale for production, that seomthing slightly larger, such as a 20700, might be more ideal.

Certainly that one pic of a specific 20700 capacity isn't the end-all of what the format is capable of, but it would be odd for the Tesla boys to suggest larger format cells might be more ideal if there's a real thermal constraint in the application, no?

 

[sorka]

What's odd is that I recall some talks/videos from either JB, Elon or both (I honestly cant remember the specifics) seemed to indicate that, although they used the 18650 as a result of the already-established economies of scale for production, that seomthing slightly larger, such as a 20700, might be more ideal.

Certainly that one pic of a specific 20700 capacity isn't the end-all of what the format is capable of, but it would be odd for the Tesla boys to suggest larger format cells might be more ideal if there's a real thermal constraint in the application, no?

Wasn't that in reference to what they plan to build at the giga factory?

 

[stopcrazypp]

What's odd is that I recall some talks/videos from either JB, Elon or both (I honestly cant remember the specifics) seemed to indicate that, although they used the 18650 as a result of the already-established economies of scale for production, that seomthing slightly larger, such as a 20700, might be more ideal.

Certainly that one pic of a specific 20700 capacity isn't the end-all of what the format is capable of, but it would be odd for the Tesla boys to suggest larger format cells might be more ideal if there's a real thermal constraint in the application, no?

I remember the same comments from JB. If there is a thermal constraint then there is much less advantage to the 20700 form factor. Theoretically there is less module overhead costs from having larger cells (less per-cell interconnects), but if cell energy density stays the same, the cells themselves likely don't cost much less per kWh (reduction in $/kWh is traditionally largely driven by energy density improvements from using less material for the same kWh).

I guess we will find out soon with Model 3 release (maybe even have hints in the March unveiling).

 

[scaesare]

Wasn't that in reference to what they plan to build at the giga factory?

My (admittedly fuzzy, given the sheer number of talks/videos I've watched the last 3 years) is that the initial discussion of optimal cell size was well ahead of any information about the GF. As a matter of fact, I think there was some significant speculation that the GF might start producing larger cells BECAUSE of JB's prior comments.

In either case, regardless of where the cells are manufactured, if the lessened ratio of surface area-to-volume is a constraint, it would have been odd for JB to have made that comment...

 

[NOLA_Mike]

Any revelations from pages 7 to 51 that I should know about? Any super critical posts to this thread that someone remembers and can throw a link in here?

No - you pretty much know as much as the rest of us that read pages 7 - 51...

 

[dhanson865]

No - you pretty much know as much as the rest of us that read pages 7 - 51...

yeah but what about pages 52 to 80?

 

[Scotty]

Some very strongly held positions on this thread.

While I say to each his own, I appreciate reading the greatly varied views.

I would like to get the usable energy out of the MS I paid for. That said, I'm looking for other examples to refute/support my position (whatever it may be)

My Dodge 3500 diesel truck has a 34 gallon tank. With consideration of fueling temperature, my 34 gallon tank holds 34 gallons, and while 100% of that 34 gallons is not available due to how the fuel pickup draws fuel from the bottom of the tank. It is consistent, though, when on the same level ground.

My Diesel motorhome, however, has a 130 gallon tank, but due to it's flat bottom design, only 105 gallons are available (for driving). If I'm running the diesel genset, however, the genset fuel pickup line is not able to draw fuel when the fuel leevel (capacity) dropa below 75%. Prevents the genset running you out of motive fuel.

My MS is rated at 265 miles range, but like an ICE vehicle, it will be more or less, depending on speed, winds, load, tire pressure, delta in altitude, road surface, climate, pack degradation, and so on. However, batteries do degrade over time and use, while my fuel tanks will be consistent in fuel capacity (short of a dented tank).

We are experiencing a major shift in ICE and BEV's, and also in the newer frontier on BEV implementation. I think there were huge disagreements during steam to diesel locomotive transitioins, gas vs diesel, AC (Nikola Tesla) vs DC (Thomas Edison), Coke vs Pepsi.....

I'm going to continue to follow this thread, even to those off-topic posts (like this one from me), but hope that Tesla addresses these topics in the future. Everyone has a bias, though, and don't think the positions I'm seeing will change anytime soon.

 

[marcmerlin]

So, I have a 90D, and the problem that I'm only seeing 75 or 76Kwh usable for driving (see details on How many Kwh usable for driving are you getting on an 85 or 90 car? (I only get 75Kwh on my 90D) ).
If my car also has a 4Kwh anti brick buffer, that means, my real pack capacity is only around 80Kwh, and I paid $3000 for the privilege of having apparently no more battery capacity than an 85D, or maybe even slightly less. I can't speak about range, calculating that is just too variable to be a useful discussion, but somehow I'm not expecting that my 90D has special changes that make it go farther than an 85D with the same batteries.
Worse, I'm actually seeing maybe 1-2Kwh usable _less_ than an 85D on a pretty new car.
See the other thread on how I calculated (I did this 4 times on 4 long legs, and the last 2 I did very carefully without stopping once).

I didn't find details on how the 90D is supposed to have an extra 5Kwh, which I'm definitely not seeing. More cells? Cells with higher capacity? other?

Thanks.

 

[Johan]

It seems to me the 90's will require not one (*) asterisk but two (**). Something is rotten in the state of Denmark...

 

[brec]

I'm very late to the party and don't have time to read through all 51 pages. ...

I feel fortunate that I changed (increased) the number of posts per page before the recent TMC forums software downgrade removed that preferences setting.

 

[brec]

I feel fortunate that I changed (increased) the number of posts per page before the recent TMC forums software downgrade removed that preferences setting.

I guess I shouldn't have posted that. I'm back to 20 posts/page. More work (requests) for TMC's forum server to supply the same data, more clicks and waiting for me.

(Off topic, but the thread seems dormant. I'll not continue these thoughts here, though.)