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

[Auzie]

@Flathill, have you ever even been in the same room as Elon, or is this all based on what you have read on the 'Net?

Anyway, this is the same old "The end justifies the means" rhetoric. My point still stands, what have Tesla done in the last year that has been in the favor of their customers?

Hmmm I find this a bit harsh

As far as anyone's contribution here is concerned, no one is offering any credentials to support their claims and perhaps there is no need to.

Poster's contributions can be judged by the content and information they present, not by association with Elon.

Every post stands on its own merit and nothing else.

Regarding pot shot at Tesla - Tesla delivered 50580 cars in 2015. I can imagine that means something to 50580 happy drivers, but I understand that may mean nothing to you.

 

[flathillll]

I was going to continue to share data and results from actual Tesla cells, actual Tesla modules, and actual Tesla packs that I've tested personally in an effort to get the thread back on topic... but never mind. I'm not wasting my time.

If one person with no first hand experience with the actual cells and data at hand is able to so badly derail the thread, and even be praised for doing the so, then I'm just wasting my time continuing to provide input here. Definitely have much better things to do. Summary of my findings remains in the first post.

Unsubscribed. You'll find no further posts on this subject from me here.

Again you have a noble purpose and it is good to share information, but to suggest Tesla has some sort of nefarious intent with regards to any of their specs is plain WRONG and I will call you out on it everytime. Why not start a new thread and focus on the data this time.

 

[JRP3]

Almost all other EV's on the market except the Fit EV use manganese based cells which are designed to fail

You should probably tell Elon that the manganese based cells he chose for daily powerwall cycling and long life are designed to fail....

In contrast, Musk said that Tesla will use a lithium-ion battery with a nickel, manganese, cobalt oxide cathode for its grid battery. Called an NMC battery, it’s meant to be used for daily cycling for a home, business, or certain types of clean power.

http://fortune.com/2015/05/18/tesla-grid-batteries-chemistry/

 

[flathillll]

You should probably tell Elon that the manganese based cells he chose for daily powerwall cycling and long life are designed to fail....



http://fortune.com/2015/05/18/tesla-grid-batteries-chemistry/

I am fully aware of the fact the powerwall uses NMC cells. What you fail to note is the 7kwh pack measures closer to double that new. The reserve can be changed with time so they can honor the 10 year warranty.

you can imagine when u bolt a battery to a wood wall safety wins out over energy density. NMC cells suck for an EV

 

[bridaus]

Isn't there room for both wk and flathilll in this thread? Wk you do a disservice to your data and cause if you give up so easily. Your data speaks for itself, and I think flathilll theories or knowledge have a place too. Nothing either of you are saying disproves the other. And if either of you could disprove the other respectfully, everyone would learn from it. Why does everyone have to take things so personally? It's the internet folks. Post away, the electrons don't hurt and data wins. I happen to think you are both right when the drama is stripped away.

 

[jcaspar]

Maybe the serval software upgrades I have gotten for my car that have cost me exactly zero $$ ??

Then please enlighten me on one thing Tesla have done in the last year that has been positive for the customer, not their headlines?

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Now this makes total since to me. Until someone can do the calculations based on the rated capacity of a new cell, all these homemade guestimations are simply interesting reading but have no real relevance to the pack rating.

The 85kwh rating is in no way a scam. That is below the true rated capacity. While Wk can claim to be Tesla battery expert, he is in no way a Tesla cell expert. He is the most valuable member on the forum, and the information he is providing is very valuable, but be careful interpreting what he is reporting.

Anyone familiar with NCA cells would know that the fact he is measuring/calculating ~81kWh on a pack over 6 months old (guessing roughtly from time of cell mfg+transport+testing+install+whatever) is actually showing Tesla has the best cells on the market. Remember Tesla's Panasonic cells are actually made by Sanyo Automotive & Industrial Systems Company. If you look at any Sanyo NCA cell data sheet you will see they only guarantee a 80% recoverable capacity with the following conditions:

1) less than one month if stored from -20 to 50C
2) less than 3 months if stored from -20 to 40C
3) less than 1 year if stored from -20 to 20C

An absolutely shite guarantee right? An that is ONLY if you store the cells at exactly the right voltage and exactly the right humidity. Yes that is the present state of the art! A one month old cells stored at 50C could lose 20% of its capacity and still be within spec!

Again ~81 kWh that Wk is measuring/calculating is phenomenally good. If the pack was brand new it would actually measure closer to 86 kwh. Wk is really doing disservice spreading misinformation by jumping to conclusions, but his cell testing cycle data will show the best thing about NCA cells is the degradation starts to level out, making them the only cells that can last ~20 years in an automotive application (estimated 70% capacity after 20 years).

Again this is how the game is played. All ebikes, power tools, golf carts, and other EV's rate their battery pack based on the rated capacity of the cell given on the cell's datasheet. Typical capacity is higher than the rated capacity.

Again the more information the better, but please don't scare people into thinking they have been scammed!

Tesla's only obligation is to rate the pack at or below rated capacity of the cells. In case of the 60 kWh model they underrated the battery for two reasons:

1) to get more people to upgrade to the 85 kWh pack (duh)

2) the smaller pack needs more leeway to ensure long life as the pack capacity will be utilized more fully more often. Tesla is hoping the packs will hit 80% (worst case usage) after 8 years for both the 85 and 60 packs. Remember the goal with the roadster was 70% after 8 years (best case usage) so this is a big jump in lifespan.

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Hear hear! I agree, both are right. I think the truth is when brand new, the pack has 85KW (or more) capacity but after sitting around for several month, it likely drops to 81+KW which is still plenty to give us the EPA rated range and more than any other production EV on the planet (ignoring the 90D and the Roadster 3.0)

Isn't there room for both wk and flathilll in this thread? Wk you do a disservice to your data and cause if you give up so easily. Your data speaks for itself, and I think flathilll theories or knowledge have a place too. Nothing either of you are saying disproves the other. And if either of you could disprove the other respectfully, everyone would learn from it. Why does everyone have to take things so personally? It's the internet folks. Post away, the electrons don't hurt and data wins. I happen to think you are both right when the drama is stripped away.

 

[JRP3]

I am fully aware of the fact the powerwall uses NMC cells. What you fail to note is the 7kwh pack measures closer to double that new. The reserve can be changed with time so they can honor the 10 year warranty.

Source?

 

[stopcrazypp]

No problem. If you are interested in why a long-term self discharge test is used by Tesla (which actually degrades the cells before they are even built into a pack and is view by bean counters as a "waste" of money)

https://batteryworkshop.msfc.nasa.g...or the Spacesuit Li-Ion Battery_JNeubauer.pdf

Tesla always prioritizes safety above all. That is why the Model 3 is not going to use prismatic packs even though it would be easier/cheaper/denser

This is the first I heard that Tesla pre-cycles their cells before putting them into a pack. I think this is a "citation required" claim.

When I looked at the NCR18650A graph 5 years ago, I took the baseline to be 5 cycles (because of the steep drop), but I didn't really expect Tesla would necessarily do that.

http://www.teslamotorsclub.com/show...or-Model-S/page2?p=61317&viewfull=1#post61317

Also on the whole 40kWh discussion. It was possible to build a 40kWh that had both longevity and performance, but would have required different cells than the 85kWh. If 40kWh made up 50% instead of less than 5% of orders, then Tesla might have went that route.

Going back down memory lane in that thread shows I speculated the 160 and 230 mile packs (AKA 40kWh / 60kWh) would use custom lower capacity cells and that they would outsell the 300 mile (AKA 85kWh pack) handily.

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Why doesn't the range drop sharply in the first few weeks or months of ownership if the cell capacity rapidly drops?

His claim is Tesla pre-cycles the cells so that they are past the rapid degradation stage before installing them into packs (and primary reason to do that is to weed out bad cells).

 

[jcaspar]

Makes perfect sense they would precycle. Who would want to see their range drop significantly in the first month of ownership, (even if it was from 300 miles to 265)

 

[stopcrazypp]

Makes perfect sense they would precycle. Who would want to see their range drop significantly in the first month of ownership, (even if it was from 300 miles to 265)

It'll be more like from 274 miles to 265 miles in the first 1000 miles or so, if using today's EPA numbers.

The 300 mile in my graph from 5 years ago is from before the new 5-cycle EPA ratings (the production Model S actually got 320 miles under the older 2-cycle tests the Roadster used).

I get your point though. It'll be very alarming to a new owner to lose almost 10 miles of range within the first month. Would be very tough to explain and keep a customer confident. Problem is 5.5x degradation rate in the first 5 cycles.

 

[Auzie]

So one person who has been against pretty much everything I've ever posted on this forum comes up with some claim that Tesla does NASA style testing on every cell with no evidence that even remotely backs this claim (I've seen zero evidence of this, nor have I even remotely heard of this with Tesla anywhere before now), posts info not even related to Tesla cells, and a link to some document that doesn't even contain the word "Tesla", let alone relates to anything Tesla does, as "evidence".

One "word": lol.
......................

flathillll's posts are as valid as anyone else's here. I do not see his posts "being against yours" in this thread. He seems to be challenging some of your interpretations, but not your results.

Even if someone contradicts your posts, most people would see that as a great opportunity to argue their points and perhaps some debaters might reevaluate their position, at least partially.

Flathillll seems to be offering expanded perspective on cells behaviour. The validity of his claim is unknown. It is as valid as anything else in this thread and in general on the internet forum like this one. It is up to each reader to evaluate the validity of anything here, without the evidence.

 

[cynix]

Maybe the serval software upgrades I have gotten for my car that have cost me exactly zero $$ ??

I'm pretty sure smac was asking if Tesla has done anything that's good for their customers but not good for their news headlines. His point was that things like free software updates, while good for the customers, are great for the headlines, so Tesla is driven by profit to do these things, not by altruism.

 

[JRP3]

This is the first I heard that Tesla pre-cycles their cells before putting them into a pack. I think this is a "citation required" claim.

A citation would be nice, but I think it would be prudent for Tesla to cycle cells at least a few times for QC, both before and after they are assembled into a pack. I'd be surprised if they didn't. On the other hand, I'd expect that Panasonic would also cycle the cells a few times and only rate them for capacity after those cycles had reduced the initial capacity.

 

[jaguar36]

A citation would be nice, but I think it would be prudent for Tesla to cycle cells at least a few times for QC, both before and after they are assembled into a pack. I'd be surprised if they didn't. On the other hand, I'd expect that Panasonic would also cycle the cells a few times and only rate them for capacity after those cycles had reduced the initial capacity.

I'd be surprised if anyone was precycling the cells significantly. It'd be a logistical nightmare if each pack or cell had to spend a couple days being cycled. Large inventories are the death of a modern production system and having a whole warehouse full of packs that are stuck for a couple of days would be a huge detriment.

Not to mention I think it would be pretty obvious to anyone who has been on our a tour if they were doing this, and its never been mentioned.

 

[scaesare]

I'm pretty sure smac was asking if Tesla has done anything that's good for their customers but not good for their news headlines. His point was that things like free software updates, while good for the customers, are great for the headlines, so Tesla is driven by profit to do these things, not by altruism.

If that's the question being asked, I can think of a couple:

-Voluntary seat latch strike plate recall

-Voluntary seatbelt recall

 

[JRP3]

I'd be surprised if anyone was precycling the cells significantly. It'd be a logistical nightmare if each pack or cell had to spend a couple days being cycled.
Large inventories are the death of a modern production system and having a whole warehouse full of packs that are stuck for a couple of days would be a huge detriment.

It wouldn't be days to put the cells through a few cycles to see how they behave, especially since that behavior is critical to the company.

Not to mention I think it would be pretty obvious to anyone who has been on our a tour if they were doing this, and its never been mentioned.

It's possible that Tesla is trusting Panasonic to do all the test cycling in advance, but I'd certainly expect Tesla to put a couple cycles on the completed packs as well. Frankly I don't see how they could not.

 

[rage_777]

So if Tesla pre-cycles their batteries, then why not measure the batteries then get them back up to 85 kWh? So, if the pack is measuring 81kWh, they should have designed it to hold more.

If flathill is saying the powerwall has double the 7kWh, why didn't Tesla think of that for the 85kWh pack and have it at 90kWh so after the pre-cycles it's now 85?

I also don't believe this stuff about its "ideal" rating is 85kWh so we'll say it an 85kWh battery. That is what a Mathematician would do not an Engineer. Theoretically the motor has 792 bhp at 0 rpms, but realistically it will take milliseconds to get there.

 

[JRP3]

So if Tesla pre-cycles their batteries, then why not measure the batteries then get them back up to 85 kWh? So, if the pack is measuring 81kWh, they should have designed it to hold more.

If flathill is saying the powerwall has double the 7kWh, why didn't Tesla think of that for the 85kWh pack and have it at 90kWh so after the pre-cycles it's now 85?

Because with the specific energy density of the original cells they really didn't have the room to over size the pack that much.

 

[stopcrazypp]

A citation would be nice, but I think it would be prudent for Tesla to cycle cells at least a few times for QC, both before and after they are assembled into a pack. I'd be surprised if they didn't. On the other hand, I'd expect that Panasonic would also cycle the cells a few times and only rate them for capacity after those cycles had reduced the initial capacity.

Well if you look at the Panasonic graph I posted, it is clear Panasonic didn't cycle their cells a few times before rating them (at least didn't cycle past the point of rapid degradation). From the NCR18650A sheet, their "3100mAh" nameplate rating is based on a brand new cell and this rating is used for retail advertising. Within 5 cycles it drops to 3000 mAh (losing 20mAh every cycle), but after that the degradation rate slows by 5.5x (to ~3.6mAh per cycle).

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So if Tesla pre-cycles their batteries, then why not measure the batteries then get them back up to 85 kWh? So, if the pack is measuring 81kWh, they should have designed it to hold more.

If flathill is saying the powerwall has double the 7kWh, why didn't Tesla think of that for the 85kWh pack and have it at 90kWh so after the pre-cycles it's now 85?

I also don't believe this stuff about its "ideal" rating is 85kWh so we'll say it an 85kWh battery. That is what a Mathematician would do not an Engineer. Theoretically the motor has 792 bhp at 0 rpms, but realistically it will take milliseconds to get there.

The Powerwall I believe is rated on usable capacity (as is most grid based energy storage) and also has a cycling guarantee (x-amount of cycles). No EV out there is rated on usable capacity, but rather on nameplate capacity. So different ratings for different applications.

 

[JRP3]

Well if you look at the Panasonic graph I posted, it is clear Panasonic didn't cycle their cells a few times before rating them (at least didn't cycle past the point of rapid degradation).

Well they have to cycle them at least once to get a rating. I think there would be at least a formation charge, a discharge, another charge and discharge for capacity and resistance rating, and then at least one partial charge to 50%. But yes that wouldn't get it past the steep loss part. Frankly there should be a baseline standard where a cell can't be marketed at a capacity if it's still in the steep loss curve.