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

[MikeBur]

Okashira,

I appreciate you laying out the case that there is room for error in wk057's data or at least that there are variables based on his methodology which he has not yet presented here. I assume that you object the spot welder comment from MikeBur, because as far as I've seen you have not stated that you have tested cells and drawn 11.9Wh from them. Will you address that aspect of his post?

If in fact, wk057's testing methodology underestimates the battery capacity in a fashion that happens to be consistent with Tesla's own BMS does it then follow that if the true capacity of the pack is 85Wh, then his calculated capacity of 61Wh for the 60 pack should actually have been ~ 64Wh?

I do find it mildly amusing that, assuming you are correct, the answer to the 85 vs 81 debate will turn out to be essentially the same as the hp debate -- the batteries could theoretically produce that much energy, just only on a test bench -- never in the actual car.

Perhaps it was the spot welder comment, though it wasn't meant in a negative way, rather reminded me of inadvertently doing a little bit of unexpected spot welding that I did when working with high current DC many years back and it made me laugh. Never thought that going misty-eyed would cause such much pith, though ho-hum.

I completely align with the belief this may well be utopic, lab-equipment-and-special-cell-criteria-required, situation. I would like to know if anyone has, and under which circumstances, proven that these cells are tested capable of 11.9Wh. I don't find that a dumb question as this would be a fundamental prerequisite for proving the capacity of this battery. I'd actually like this to be the case, though fear this is not.

 

[jcaspar]

No. Just not paranoid that Tesla is out to deceive the public with a devious plan to make their cars look so much better than the nonexistent competition. I will give them the benefit of the doubt till someone can actually find the rated capacity of the cells. I trust Tesla (the world renown leader in EVs) much more than some Joe with a vendetta against Tesla in his garage with a multimeter.

And whether my battery tests at 85, 80 or even 70 after over two years of ownership, it still has an amazing range, every bit as much as I was promised and expected. No ignorance here, but it is blissful!!:biggrin:

So you blindly trust numbers from manufacture? This is the point of this thread saying the numbers are funny. I guess ignorance is a bliss for some.

 

[dsm363]

Isn't that exactly the problem? Whilst the total capacity of the individual cells may add up to somewhere around 85kWh, we didn't buy a truckload of cells. We bought a car, and the car as a whole only has 81kWh (as reported by its own systems).

And I bought a 1TB hard drive that will never give me 1TB of storage of actual files.

 

[flathillll]

This is the most sadly comical quote from the expert:

"The car's BMS also reports the usable capacity as around 76.5 kWh with a 4 kWh buffer on my own car. See my CAN deciphering document for my CAN deciphering document which includes how to decode this data. The fact that the car reports these values that match perfectly (within 1%) of my cell testing means that Tesla is well aware that these are not actually 85 kWh packs."

The fact his BMS reading matches his cell testing tells you instantly his cell testing was done wrong. The BMS does not report the ideal (spec) capacity, it estimates the capacity based on an algorithm with inputs such as coulomb counting (current readings), resting and dynamic voltage readings, use history, cell modeling (look up tables), etc

 

[JRP3]

I may have missed it but do we have CAN data from a 60 car?

 

[MP3Mike]

70,000 Wh/ 6216 cells = 11.26 Wh/cell

85,000 Wh/ 7104 cells = 11.96 Wh/cell

60,000 Wh/ 5376 cells = 11.16 Wh/cell

Since everybody says the cells are the same between the 60, 70, and 85 packs this is very interesting... So what are they? 11.16, 11.26, or 11.96? Given that the 60 and 70 essentially match, I'm going with that they are correct and that the 85 kWh pack is misrepresented.

It will be really interesting to find out more about the 90 kWh pack...

 

[kennybobby]

... I trust Tesla (the world renown leader in EVs) much more than some Joe with a vendetta against Tesla in his garage with a multimeter.

Don't know who you think is 'some Joe...', surely not wk057 who has one of the highest reputation levels on this forum (only Bonnie has a higher rating).

 

[Auzie]

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

What is short sighted is testing OLD, USED and CYCLED cells with non-representative procedure and proclaiming the result to be bona-fide proof of anything.
..................

A little knowledge is much more dangerous than no knowledge.

This pretty much sums it up.

It is unknown how old the tested cells are

It is unknown how much the cells were used prior to being tested

It is unknown how many cycles they went through

The procedure, method or instrumentation are unknown

Even the raw measurement data is unavailable

One does not need to be a battery expert to know that the cell age, cycle count and use will be reflected in the measurement results, let alone all other factors that okashira outlined in his post

It defies logic to publicly proclaim confident conclusions based on determining cells capacity with some secret method/instrumentation and with so many unknown variables unaccounted for.

 

[Pollux]

There could even have been countervailing weight increases, so that the net gain/loss today relative to 2012 is small. For example: titanium underbody shield.

Alan

I think you've drastically misinterpreted what was actually said. Let's review:



As I've been saying.


[/B]So he's clearly saying there are a number of different components that they have been tweaking to make a bit lighter, yet you are trying to ascribe any and all possible weight reduction to the battery pack. That is obviously not the case.



Again, as I've been saying.

So in summary, any weight reduction in the car has minimal impact on range, and, most importantly, any weight reduction is the result of improvements in many of the car's components, not just the battery pack, and no evidence that it's from a reduction in pack capacity. There is also no support for your guess of 350 lbs of weight reduction, it could be as little as 200 lbs, though there are no figures which I can find to even support that.

 

[okashira]

Possible. Elon did mention that they started using a bit of silicon in the anode when introducing the 90 kWh packs last July.

Thanks for getting into the 70 and finding out about the pack--everybody has been dying to know.

So the M70 cell count would be 14 x 444 = 6216.

70,000 Wh/ 6216 cells = 11.26 Wh/cell

85,000 Wh/ 7104 cells = 11.96 Wh/cell

60,000 Wh/ 5376 cells = 11.16 Wh/cell

Somebody better peer-review my math--my sliderule is getting rusty and hard to read

oops sorry, left out the 90

90,000 Wh/ 7104 cells = 12.67 Wh/cell

They are the same cells.
They dont use different cells in the different packs...
The killed the 60 and just so they could use the same modules and not the bastard modules with missing cells.
They didnt want to call it a 74kWh or 75kWh for marketing reasons ...
The 70 pack is underrated
the 85 pack is possibly a little overrated

 

[cynix]

And I bought a 1TB hard drive that will never give me 1TB of storage of actual files.

That 1TB hard drive is guaranteed to come with at least 1,000,000,000,000 bytes. It usually comes with a bit more, for example when you plug it in the computer might report 1,000,000,218,095 bytes (number is made up, but it's the right magnitude). In fact, it usually comes win quite a bit more capacity they you can't see, as there are reserved sectors used to silently remap bad sectors (kind of like the "bricking protection" capacity, except that hard drive manufacturers don't count them as part of the advertised capacity, unlike Tesla). If there was a file system that had zero overhead, or if it's used to store raw data without a file system, then you could store 1TB of data on it. You might think that's a contrived example, but at least it's achievable (and requires no alterations to the physical hard drive as sold).

On the other hand, if the Tesla cell capacity are indeed overrated and the true capacity is indeed 81kWh, then there's no possible scenario under which you'll get 85kWh out of them, without altering the physical car as sold. You may say you can get 85kWh by pulling out the cells and discharging them at a certain rate down to 0V or something like that, but it's not possible to perform this in the car as sold, and therefore irrelevant to the average consumer.

This seems to be very similar to the 691hp debate. Sure there may be some way of achieving the rating, but not in the car as sold, and even the car's systems reports so.

 

[Cottonwood]

Thanks for getting into the 70 and finding out about the pack--everybody has been dying to know.

So the M70 cell count would be 14 x 444 = 6216.

70,000 Wh/ 6216 cells = 11.26 Wh/cell

85,000 Wh/ 7104 cells = 11.96 Wh/cell

60,000 Wh/ 5376 cells = 11.16 Wh/cell

Somebody better peer-review my math--my sliderule is getting rusty and hard to read

oops sorry, left out the 90

90,000 Wh/ 7104 cells = 12.67 Wh/cell

Interesting numbers...

Here is some simple ratio logic:

The ratio of modules between a 70 and an 85 is 14:16; the ratio of cells between a 70 and an 85 is 6,216:7,104. Both of those reduce to a 7:8 ratio. Therefore, given that the same cells are used, it seems the pack ratings should also be a 7:8 ratio or 70:80.​

 

[dsm363]

That 1TB hard drive is guaranteed to come with at least 1,000,000,000,000 bytes. It usually comes with a bit more, for example when you plug it in the computer might report 1,000,000,218,095 bytes (number is made up, but it's the right magnitude). In fact, it usually comes win quite a bit more capacity they you can't see, as there are reserved sectors used to silently remap bad sectors (kind of like the "bricking protection" capacity, except that hard drive manufacturers don't count them as part of the advertised capacity, unlike Tesla). If there was a file system that had zero overhead, or if it's used to store raw data without a file system, then you could store 1TB of data on it. You might think that's a contrived example, but at least it's achievable (and requires no alterations to the physical hard drive as sold).

On the other hand, if the Tesla cell capacity are indeed overrated and the true capacity is indeed 81kWh, then there's no possible scenario under which you'll get 85kWh out of them, without altering the physical car as sold. You may say you can get 85kWh by pulling out the cells and discharging them at a certain rate down to 0V or something like that, but it's not possible to perform this in the car as sold, and therefore irrelevant to the average consumer.

This seems to be very similar to the 691hp debate. Sure there may be some way of achieving the rating, but not in the car as sold, and even the car's systems reports so.

But as the battery pack is sold in a car you drive just as the hard drive is sold in a computer (usually) that has a file system and an OS on it with overhead yet Apple and others still advertise 1TB for example. If it's true that Tesla came up with the number adding together the cell ratings straight from Panasonic that quickly become not accurate once they are cycled in a battery pack then I see that as similar. Sure, a more accurate rating would be better but as long as the EPA range rating is accurate that's what really matters.

 

[cynix]

But as the battery pack is sold in a car you drive just as the hard drive is sold in a computer (usually) that has a file system and an OS on it with overhead yet Apple and others still advertise 1TB for example. If it's true that Tesla came up with the number adding together the cell ratings straight from Panasonic that quickly become not accurate once they are cycled in a battery pack then I see that as similar. Sure, a more accurate rating would be better but as long as the EPA range rating is accurate that's what really matters.

The hard drive that came with a computer can be erased and used for full capacity if you wanted to. You can't do that with a Tesla battery pack.

Your EPA range rating comment shows that this is again very similar to the 691hp controversy. Tesla is (most likely) technically in compliance with laws/regulations/standards, it's just that these laws/regulations/standards are not what the consumers expect.

 

[Auzie]

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

Your EPA range rating comment shows that this is again very similar to the 691hp controversy. Tesla is (most likely) technically in compliance with laws/regulations/standards, it's just that these laws/regulations/standards are not what the consumers expect.

That seems to be the crux of the issues.

Incorrect interpretations and expectations lead to disappointment.

Consumers expect specifications to be simple, reproducible and precise. That is possible to achieve with simple products, say milk. It is easy for consumers to repetitively check packed volume and get the same result.

More complex products have more complex specifications that can only be precise in a narrow set of controlled conditions that are not easily reproducible in real world conditions.

 

[JRP3]

We've always known that Tesla, or any EV, doesn't allow full use of the pack, and the consumers have been fine with it.

 

[bluetinc]

If someone buys a Mustang 5.0L but if when measured the engine is only 4.0L (all other specs are met just as before, hp, 0-60, mpg, etc.), does no one care, or is Ford in trouble?

 

[bridaus]

If someone buys a Mustang 5.0L but if when measured the engine is only 4.0L (all other specs are met just as before, hp, 0-60, mpg, etc.), does no one care, or is Ford in trouble?

Ahh, some math I can help with!

4/5 = 80%
81/85 = 95.3%

So its more like a 4.76 liter engine was sold

That's if you take the OP data at face value...

Less to write home about eh?

Oh and BTW, I don't care about how many liters, I care about power. But wait, you're telling me I'm sold a 500hp car, and I put it on a dyno and it measures MUCH less!!!! I've been robbed!

The drama in this thread is annoying, unnecessary, antagonistic, and meant to harm therefore shameful. However the data is brilliant, so lets keep at that!

 

[cynix]

More complex products have more complex specifications that can only be precise in a narrow set of controlled conditions that are not easily reproducible in real world conditions.

The car's system is perfectly happy with reporting a full capacity of 81.x kWh, just as it was perfectly happy with reporting a maximum power of xxx hp (the precise number escapes me at the moment). Regardless of how these values are measured/calculated/estimated, if that's how Tesla chose to measure/calculate/estimate them, it's how they should advertise them.

 

[ChadFeldheimer]

Interesting numbers...

Here is some simple ratio logic:

The ratio of modules between a 70 and an 85 is 14:16; the ratio of cells between a 70 and an 85 is 6,216:7,104. Both of those reduce to a 7:8 ratio. Therefore, given that the same cells are used, it seems the pack ratings should also be a 7:8 ratio or 70:80.​

When I bought my car, I debated whether to spend $10,000 for the extra 15kwh (and the additional advertised range and acceleration) advertised on the 85 over the 70. At the time, I calculated that the EPA estimated range on the 85 did not represent an increase over the 70 that was proportional to the increase in rated battery capacity.

This puzzled me.

I knew that the additional weight from the cells should not negatively impact range to the extent predicted by the EPA range estimate, so it was unclear what was driving the discrepancy. In the end, I chalked it up to some oddity in the EPA test cycle. I knew that ICE manufacturers game the cycle with well tuned gear ratios for specific portions of the test, etc - so perhaps some aspect of their test is much more amenable to the 70 versus the 85. No one really puts that much faith in EPA mpg numbers anyways (only useful as a very loose comparison between cars) - so why would the rated range on an EV be any different?

In the end, I spent the extra cash on the 85kwh upgrade.

As a result of the findings in this thread, I'm convinced that regardless of whether or not the 85's 85kwh battery is "correctly" rated, it is "aggressively" spec'd relative to the 60 and 70 - to the extent that those that paid $10k for the 85 over the 70 received only 2/3rds of the bargain (~10kwh instead of 15kwh).

Personally, it leaves a bad taste in my mouth, and I'll certainly keep this experience in mind for the future. Fool me once...