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

[smac]

Sorry for duplicate posting, but it seems to me Tesla did a "DeWalt" on this one:

18v vs 20v Lithium Ion Power Tools - The Truth Uncovered - YouTube

Interesting conundrum for them in the EU as they probably don't have the leaway to stretch the specs to the same levels. (Hence why Dewalt 20v are correctly sold as 18v here )


Why o why o why, did they do this? It made no sense. The car is so good as to not need this sort of bullcr@p.

Maybe I should just be happy as a 60 owner to have received more battery than I ordered. However this (+all the other stuff that has come to light) has really tainted my view of the company, to the point my next car is unlikely to be a Tesla.

 

[Troy]

Why o why o why, did they do this? It made no sense. The car is so good as to not need this sort of bullcr@p.

Maybe Tesla was afraid of competition. This statement certainly gives that impression:

Elon (June 2014): At Tesla, however, we felt compelled to create patents out of concern that the big car companies would copy our technology and then use their massive manufacturing, sales and marketing power to overwhelm Tesla. Source

Mercedes had a small EV called Smart Electric Drive. Tesla made the battery for that car (source). At the time it looked like Mercedes was testing the technology in a small car and then maybe they might build a larger EV themselves, potentially one with 80 kWh battery. When the Model S was released there were no superchargers. Tesla didn't have any clear advantage over known brands.

I think Tesla's original plan was 40, 60 and 80 kWh versions. But then it looks like they decided it was OK to advertise 85 kWh because that was the maximum capacity at certain temperature and voltage. This sounds similar to electric motors having the potential to produce a certain amount of horsepower in ideal conditions that can't be practically achieved.

What I find even more interesting is the mismatch between EPA certified rated miles and displayed rated miles in the car. These are not the same. The S85 has 265 miles EPA rated range and the dashboard shows 265 miles. However, the EPA test includes the extra reserve below zero rated miles. That means the dashboard should display less than 265 mi rated range because not all rated range is available to the end user without going into reds. It would be more accurate if the S85 displayed 248 rated miles and it was explained to the end user that the other 17 miles was reserved to improve battery life. This issue is best explained on this page before the battery diagram.

From EPA's perspective, there is no problem because the capacity is available to the end user, even if it's not clearly displayed and the end user is not aware of it. They don't want to get involved in display methods each car manufacturer uses. The problem is, it is impossible to measure battery degradation from range. Over time the computer could reduce the reserved rated miles (maximum 17 miles) to compensate for part of the degradation and the end user wouldn't know that. For example displayed rated range might drop from 265 to 260 miles in two years. That's what the end user sees. It doesn't look so bad. However what the end user doesn't see is, the reserve might have dropped from 17 rated miles to 5. There is no way to know that.

(Update): Above I said S85 should display 248 mi rated range because the 17 mi reserve is included in EPA testing. However I forgot something else that is included. Jerome Guillen from Tesla said "EPA testing is with range mode on" (Source). Therefore a new S85 should display 248 mi rated range with range mode on and 244 when it's off. I think that would be the most accurate thing to do.

 

[Scotty]

wk057, Thanks for the info. Here's my 2 cents worth.

The comparison about engine size of ICE vehicle model vs engine size is tenuous. on a Mercedes 300 being a 2.8 litre or 3.0 litre is immaterial, since the engine displacement was inferred in the model number. You could say it's assumed on my MS, which just has the badging '85'. However, all of the specs state that my MS has an 85kWh battery pack, vs the 60 that was also offered. Would anyone on this forum be accepting of a financial institution promising you 10% return, in writing and verbally, but only delivering 8% Sure, it might be a better rate than ANYONE else offers, but is this acceptable to you, and would you trust them in the future, and do repeat business?

How about the ICE gas tank capacity analogy mentioned previously. That doesn't work in regards to BEV's.
- If I take an ICE car with a 12.0 gal tank, fill it to the maximum amount, and then drive til empty, and repeat this numerous times, this fueling and driving cycle will have zero impact on the ICE vehicle's range and life expectancy. However, charging a MS to 100% range charge, and driving to 0 miles does degrade the range and life expectancy of the MS battery pack, particularly if done repeatedly. Even the MS warns you about repeated range charging.
My concern, however, is in comparing an 85kWh pack to an 81kWh pack... promised vs delivered. This will impact range degradation and life expectancy. My MS was to be delivered with the 85kWh pack, but this was stated on the window sticker. (Now, we all know that not delivering on those window stickers tends to draw the scrutiny of the EPA and/or the FTC. When my wife's Ford C-Max didn't deliver the mpg that the vehicle sticker stated, Ford sent me a check for $500, which was their estimate between the estimated mpg and the actual mpg, and the taking into account fuel cost estimates and total driving expectancy). I found this satisfactory.
However, we both had previously purchased new 2008 Honda Civic Hybrids and both suffered from premature battery degradation. Honda uploaded new firmware into the vehicles when they were in for oil changes, which disabled Integrated Motor Assist whenever the battery pack was at or below 50% on the 8 segment battery meter. I had to fight tooth and nail with Honda to replace the battery packs, even though both were under California state law as part of the California warranty laws regarding hybrid vehicles. Honda lost my trust, and all future business.
A BEV which has a larger capacity battery pack will provide more usable energy than a smaller one. If the battery pack is operated between, say, 30.0% and 70.0%, the larger pack will go further than a lower capacity pack, or will go the same distance without discharging as much. Longevity is related to not charging higher or discharging lower than recommended.

Finally, it's obvious that a P85D will put a larger load on the pack upon full acceleration than a 'plain 85 does. Although I have the 85, I think the stress on full acceleration utilizing a larger pack will lead to longer battery life. The smaller usable battery pack is a concern for me. I bought my MS to drive for years. 16 months and 56K miles is just breaking it in. While there's always the option of just 'unloading' my MS and upgrading (what quite a few P85 owners did when the D was released) that's not a preferred option for me.

Finally, all kinds of sayings come to mind. Ignore the following if they seem inappropriate or a waste of your time, particularly about .Tesla and it's marketing.

You can fool some of the people some of the time, but not all of the people all of the time.
Caveat Emptor
You reap what you sow
A man's word is his bond
1 aw sh!t, wipes out 10 attaboys.
How about fool me once shame on you, fool me twice, shame on me

 

[schonelucht]

Why o why o why, did they do this? It made no sense. The car is so good as to not need this sort of bullcr@p.

Is in not blindingly obvious? Marketing. Tesla wanted us to buy an 85 over a 60 because it's better for their ASP, their margins and their contractual obligations towards Panasonic. Sure, we all claim we don't fall for that trap and made our decision strictly based on independently verified stats (big grain of salt right there?) but the reality is most people really aren't that calculated. Buying is emotional and the headline numbers game works irrespective of the underlying reality enough to make it significant. 85 sounds better than 80 compared to 60 so it influenced a number of buyers to pick an 85 over a 60. There is really nothing more to it. Exactly the same reason Tesla reported various performance measures for the P85D model with different methodology than for other models, btw. There is not a single shred of doubt for me that these were calculated decisions somewhere in the Tesla organisation.

 

[supratachophobia]

It's possible that the 90 pack upgrade represents a better capacity value than is represented in the 5kWh bump, then. Making the assumptions that wk057's data is valid (I trust it) and that the 90 is really 90. But, as was mentioned above, are you buying it for the capacity or stated (and more importantly, realized) range?

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.

As for what we can do, just be frustrated I guess. I do feel very misled. And as wk said, I would be very distrustful of future numbers that Tesla releases. But also as he said, why lie in the first place? The car is an excellent 80kw car, just be truthful.

- - - Updated - - -

OMG -- they rounded 81 to 85? -- heaven forbid! And they did it just to be intentionally deceptive, with the goal of ripping us all off of our hard earned money. Because no one ever would have bought the car if we knew this fact! Right! It's exactly as you surmise, but thankfully we have you to be the "BATTERY SUPERHERO!" who came to save the day! And to think you would have never found this out if you only kept your word and never bought another Tesla product, like you promised us...

Stop the Press! Tesla announces REAL HP numbers for P85D and P90L - Page 222

Stop the Press! Tesla announces REAL HP numbers for P85D and P90L - Page 225



Yeppers. It's sure gone downhill fast. Comical really.

I don't appreciate your tone. Tesla did not tell the truth, period. And the sad part of that is they didn't have to lie about it.

- - - Updated - - -

based on an Elon Musk comment (I believe about a year and a half ago), since the Model S was introduced in 2012, the vehicle has dropped a few hundred pounds. what's more, there has been a series of different battery packs.

isn't it possible that,

-the early 2012 Model S were built to use XY kWh of a battery pack that really was 85 kWh, as Tesla determined that XY kWh usable got them to a range that would hit an EPA number (265 miles) they selected for the biggest battery.
- as battery chemistry and/or pack design, management was tweaked, and weight came off the car from continual changes across the design of the car,
1. lower weight meant that a usable capacity lower than XY kWh was sufficient to deliver the same range as the original battery pack that actually had 85 kWh
2. newer battery chemistries came with improvements that allowed Tesla to increase the percentage of the battery pack available to use
- over time, these changes would mean that Tesla went from an 85 kWh battery pack to various small changes up through the one you tested and measure as 81 kWh. they didn't change the Model S 85 kWh offering to say, an 83.6 kWh Model S, then an 82.9 kWh Models S, etc... but rather knew they were delivering the same range as the original 85 kWh battery.

just to say, having spent all of ten minutes thinking about it (and not even having the knowledge to consider possible errors in your testing or calculations), there may be other explanations to this. not saying I disagree with your posting this, and raising questions.

update: re point 2 above... more broadly, a variety of potential changes to the battery pack, whether a newer cell chemistry, newer battery management, cooling, or other, that allowed Tesla to feel confident making a larger percentage of the pack available for use in propelling the car. what letter battery pack are we up to now since the original "A" pack? clearly there have been changes, and there may well have been changes allowing more of the battery to be safely used.

That is an excellent point. They have at least 5 different versions of the 85kw pack, is it possible the cells themselves have subtle differences across revisions?

 

[tstafford]

It's strange to me how Tesla persists in implying things about the car that aren't 100% accurate despite the fact that the accurate information itself is compelling. It's almost pathological.

 

[Max*]

Nice write-up. It's always interesting to see the real numbers, from a scientific perspective; but I also agree with you and everyone else that it's not a deal breaker. It's deceptive marketing, but... what can you really do?

 

[smac]

Nice write-up. It's always interesting to see the real numbers, from a scientific perspective; but I also agree with you and everyone else that it's not a deal breaker. It's deceptive marketing, but... what can you really do?

Short of voting with your wallet not much. With no real EV competition right now the only option is to spend less on your next Model S.

Personally I'd happily make do with a plain old 77 rather than a P??D until they start being less "over optimistic" with their marketing specs

 

[AWDtsla]

That is an excellent point. They have at least 5 different versions of the 85kw pack, is it possible the cells themselves have subtle differences across revisions?

Do any of the cars display different Wh/mi rated or different rated miles at 90/100%? I believe the answer is no, then they are all claiming equal usable capacity.

Basically no rocket surgery needed to figure out useable capacity is exactly what wk057 stated. You couldn't however have know exactly why the difference exists from the nameplate rating.

 

[scaesare]

As has been commented on, there are 2 related issues at hand:

Actual Rated Cell Capacity:

I tend to agree with stopcrazypp below that this is likely a pass-on of the rated capacity of the cell from Panasonic:

This is exactly the issue I suspected. I am 100% aware that taking "nominal voltage * Ah" does not give the "true capacity" (to get that you have to integrate the area of the curve). However, that is how nameplate capacity is determined typically.

Also the test below measured 12.142 Wh from a NCR18650B. Your methodology underrates the cell 1.52% compared to that test (and the below test actually doesn't give the full capacity since cut-off is at 2.8V instead of 2.5V and the cell is a protected cell so has additional energy loss)
http://lygte-info.dk/review/batteries2012/Panasonic NCR18650B 3400mAh (Green) UK.html

Compared to nameplate method (12.24Wh vs 11.96Wh) the difference is 2.34%.

This spec sheet confirms the numbers being discussed for the the NCR18650B, which is rated at 3.6V x 3350mAh = 12.06W. And while we all understand that the area integrated under the curve is a more realistic number (that takes in to account energy lost to internal resistance, etc..), this is the commonly accepted way to spec a cell. It's pretty close to the actual energy the cell stores, but not what you can really ever get out of it.

Assuming the Tesla cells are similar to the 18650B, they could be rated slightly less at (85000W / 7104) / 3.6V = 3325mAh and be be "true" to spec.

If this is the case, I'm OK with it. If we determine that the cell is actually rated at anything less than 11.9W (just over 84.5KWh) or so from the manufacturer, I'd consider that somewhat deceitful. I agree with the comments that, while model names and designations can be fanciful and made-up, specifications matter and should be accurate. Car manufacturers have been sued over false HP claims, for instance.


The second issue is:

Actual Utilized Capacity:

Trading off one aspect of unit capability in order to optimize other characteristics (i.e. capacity utilized per charge vs. cell longevity) is a trade-off made in engineering all the time. Deciding to maintain a buffer in order to avoid bricking is a reasonable design consideration for a vehicle, given the physics presented by rechargeable cell chemistries.

Would I prefer that everybody (cell and product manufacturers alike), provide the actual spec for what they use in addition to absolute max available? Sure... and some manufactures do (a separate "usable" rating), but not including it is relativle widely accepted, and doesn't fall in to the realm of deceit, IMO.


I appreciate WK's reporting his findings, and agree there's reason for concern based on what I outlined above... I suspect it would take finding out Panasonic's actual specs for this specific model for me to settle how I feel about it.

For those who aren't concerned, great. Just do the rest of this who are interested in the technical underpinnings, and move on rather the post jabs, eh?

 

[bonnie]

For those who aren't concerned, great. Just do the rest of this who are interested in the technical underpinnings, and move on rather the post jabs, eh?

I've been staying out of this and the other thread. But I do have to respond to this. I know of two journalists who were contacted a few months back and then another contacted recently (and not to say there weren't more - only the ones I know about), pointing to *these threads, for the purpose of trying to convince a journo to write a story about it.

I'd be fine with this just being a technical discussion. But when someone is trying to use the technical discussion for another purpose, then imo opposing views are necessary. And no, not every view (agreement or opposing) has to meet some standard. Open forum, threads are open to all. If it gets off-topic or vitriolic, a moderator will likely step in.

 

[apacheguy]

Regarding NCR18650B - Sure, those cells may have lower resistance, but what's their cycle life? Heat tolerance? Charging rate tolerance? I find it difficult to believe that a stock, off the shelf cell is better all around than Tesla's proprietary cells. I mean why expend all the effort if in the end you could have bought a better product directly from the same supplier? There has to be something more to it.

Digging up relevant info buried in this fast growing thread:

In any case, my tests of the Tesla cells are very consistent and show steady degradation. I think if I continue long enough the NCR18650B and the Tesla cells will actually meet on capacity since the Tesla cells are degrading a hair less per cycle than the Panasonic cells. But, again, I don't want to dive too much into my test results until they're finalized.

 

[JohnSnowNW]

For those who aren't concerned, great. Just do the rest of this who are interested in the technical underpinnings, and move on rather the post jabs, eh?

I believe I already covered this. There is no issue with a technical discussion, but I don't actually believe that was the aim of this thread. Especially considering the first post.

Also, if you truely want to have a technical discussion, and you want to choose who should or should not respond, how about we include those that immediately lead with "Tesla is cheating me!" Then again, this is what the thread was started to accomplish, so...

 

[ohmman]

I'd be fine with this just being a technical discussion. But when someone is trying to use the technical discussion for another purpose, then imo opposing views are necessary.

I think this is an important point not just here in this thread (and all threads on TMC), but in all interactions. Even the most neutral of storytellers have a narrative - that's what makes something a good read. Determine the narrative early on, and read within the context of the narrative the author is framing. In a forum like this, if you feel the author is not being fair with their facts, attack the facts or the narrative, not the author. Dismissing claims out of hand also does little to support the other side of the argument.

 

[rage_777]

My 2 cents:

1Tb hard drive does not equal 1,000,000,000,000, it is 2^40 = 1,099,511,627,776.

I think Tesla has said that they don't use the 18650 cells, they have Panasonic modify it a bit. Not sure if they do anything capacity wise to it, doubt it, but just throwing that out there.

WK is not saying "Tesla sucks", he is saying just be upfront about these numbers that Tesla keeps throwing out there.

I know Elon is a scientist and as a scientist he should know that numbers matter. Math is not based on opinions it's based on facts and the facts are that the 85kWh battery is not 85kWh, the 691 hp number wasn't 691 hp, the 0-60 times included the 1 ft roll out, etc. Maybe Tesla needs to start saying these are theoretical numbers, not actual.

 

[JRP3]

Actual Rated Cell Capacity:

I tend to agree with stopcrazypp below that this is likely a pass-on of the rated capacity of the cell from Panasonic:

But then why the slight under rating of the 60kWh pack but over rating of the 85kWh pack? Unless they initially took the ratings from Panasonic and started designing the "85" pack and then realized it didn't reflect real world and down rated for the 60 pack. I can't remember if marketing for the 85 pack preceded the 60 pack.

 

[Max*]

1Tb hard drive does not equal 1,000,000,000, it is 2^30 = 1,073,741,824.

I'm surprised it took 77 posts to get here.

I was surprised by the comment wk made, but I understood where he was going, so I didn't comment on it.

 

[Lesifass]

As has been commented on, there are 2 related issues at hand:

Actual Rated Cell Capacity:


Actual Utilized Capacity:

I'd say there is a third, non-technical issue: Either the 60kWh or the 85kWh pack is a lie. Depending on how to correctly specify the pack size, the 60 should be 65, or the 85 should be 80, if the measurements are correct.

 

[scaesare]

I've been staying out of this and the other thread. But I do have to respond to this. I know of two journalists who were contacted a few months back and then another contacted recently (and not to say there weren't more - only the ones I know about), pointing to *these threads, for the purpose of trying to convince a journo to write a story about it.

I'd be fine with this just being a technical discussion. But when someone is trying to use the technical discussion for another purpose, then imo opposing views are necessary. And no, not every view (agreement or opposing) has to meet some standard. Open forum, threads are open to all. If it gets off-topic or vitriolic, a moderator will likely step in.

Fair enough, but to be specific, I'm not talking about posts such as:

Which is how I feel about (*) in general now...thanks to this forum.

I don't personally have as much interest in the specifics of original seats, vs. next gen seats, yet some are passionate about it. I don't wade in to their threads and disparage folks for discussing the inticracies of it. I simply ignore what I don't care about.

This topic by implicitly has (at least) two components: what are the technical facts?, and how do persons feel that has impact to them?

Certainly many views are going to be expressed on an open forum, especially for the latter. I believe I even presented some such in my post above. But there's a difference between cogently present your view, and wading in with your rather condescending JPEG.... or the rather insulting:

OMG -- they rounded 81 to 85? -- heaven forbid! And they did it just to be intentionally deceptive, with the goal of ripping us all off of our hard earned money. Because no one ever would have bought the car if we knew this fact! Right! It's exactly as you surmise, but thankfully we have you to be the "BATTERY SUPERHERO!" who came to save the day!

All that does is lower the SNR.

Finally, I'm not fond of letting the idea of what others are going to (mis)report determine what conversation (pro or con) what reasoned discussions folks can have, even if I don't like what sensationalism they may come up with (although perhaps I'll adopt the footnote disclaimer many have used.)

What I do agree with you on that front, however, is making hyperbolic posts that are sure to incite bad press, i.e.-"Tesla battery packs can blow you to smithereens if overcharged, OMG!!1one!"


------------------SEPARATE REPLY (I hate the forum does this)-----------------

But then why the slight under rating of the 60kWh pack but over rating of the 85kWh pack? Unless they initially took the ratings from Panasonic and started designing the "85" pack and then realized it didn't reflect real world and down rated for the 60 pack. I can't remember if marketing for the 85 pack preceded the 60 pack.

A good question.

If I had to guess, I'd say that with the 85, they were balancing space constraints, range (i.e. utilized power), longevity, and safety (i.e. anti-brick buffer). As they fit as many cells as they possibly could (7104) in the casing if the large pack, they had to then make ta call as to what were the acceptable margins for those other parameters. They felt they really HAD to reserve 4KWh for buffer, etc... and that HAD to come out of the 85KWh total capacity, as there was just no more space for more cells.

For the 60, I expect that they may have recognized that, with the lower range, many folks might push it farther/harder (i.e- lower overall depth of discharge, more range charges, greater power discharge for simialr acceleration characteristics, etc...) , and they had the room to reserve some of that buffer "outside" the utilized capacity, so they opted to under rate the pack a bit to meet those goals.

In other words, I allow for the possibility of the 85KWh pack to be "technically correct", and the 60KWh pack to actually be a bit generous with us.

 

[MP3Mike]

Regarding NCR18650B - Sure, those cells may have lower resistance, but what's their cycle life? Heat tolerance? Charging rate tolerance? I find it difficult to believe that a stock, off the shelf cell is better all around than Tesla's proprietary cells. I mean why expend all the effort if in the end you could have bought a better product directly from the same supplier? There has to be something more to it.

Maybe because Tesla wanted the cells to be cheaper? I can't remember for sure but the Tesla cells are completely unprotected, are the NCR18650B cells protected?