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

[stopcrazypp]

Was there another set of test data than what you posted here last year? This looks more like 3Ah x 3.6V = 10.8 Wh

LOL. So let's do a quick hand integration and arrive at Wh by subtraction. Take the two limits, 4V and 3Ah, that is 12Wh. Since we have a curve we know it MUST be a value less than that. OK, now each square is .2V*.2Ah=0.04Wh. Now count all the full squares between those lines and the top curve, estimating on the semi full ones, and subtract from 12. I got 10.96Wh. Or 77.8kWh for an 85 pack with 7104 cells.


Hmmmmm

Look at test conditions. That is 1A discharge at the slowest one. You aren't going to get the nameplate capacity of any cell at 1A discharge. That test was what I referred to before, where he wasn't trying to get max capacity. To do that most testers use a 0.2A load (he suggested even lower up thread).

For reference, the EPA UDDS cycle is 19.6mph average speed and Model S gets 320+ miles on it, so 16+ hours of discharge, probably 17+ hours if looking at nameplate (AKA C/16 to C/17 discharge). That nicely works out roughly to 0.2A for the cells in question.

 

[MikeBur]

Let me get a new cell in my tester, I am sure I will get 11.9Wh out of one. ;-)

Btw: Model S modules make for a great power supply for a spot welder: )
I have pulled 3,900 amps welding straight to the bus bar. Good thing for only 9ms.


Endless-sphere.com View topic - Tesla Model S 18650 Cell Test Data

Thanks Okashira,

Have you measured 11.9Wh out of one of these cells? I didn't actually see the answer in this, though may have missed it from the tears of laughter, thinking about the next potential Darwin Award for "Battery-powered spot welder", blurring my eyesight... .

The only thing I could find was your old chart, though I need help agreeing to 11.9Wh from that

 

[pupik]

LOL. So let's do a quick hand integration and arrive at Wh by subtraction. Take the two limits, 4V and 3Ah, that is 12Wh. Since we have a curve we know it MUST be a value less than that. OK, now each square is .2V*.2Ah=0.04Wh. Now count all the full squares between those lines and the top curve, estimating on the semi full ones, and subtract from 12. I got 10.96Wh. Or 77.8kWh for an 85 pack with 7104 cells.


Hmmmmm

Yes, almost so say Tesla CANbus my P85D with 10000 miles :wink: So, the old fact...
first question is 77.8kW + 4kW or 77.8kW - 4kW buffer
second question is how much say CANbus in your P90D ??????????

 

[Auzie]

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

No, just done having to defend my data and conclusions against people with no credibility................

I can only imagine how Tesla engineers must feel if they have a spare moment to read this forum

...This was obviously my attempt to show that the capacity difference was significant, using a monetary value derived from Tesla's own pricing, for folks who may or may not have understood the delta.....I could care less about the implications of what the data tells. The data says that customers never received a pack that Tesla labeled "85 kWh" that could actually be charged to 85 kWh in or out of the vehicle. That's a fact based on mountains of data..............Instead it's data that shows that the spec doesn't match the advertised spec........

I'd be very careful when publishing statements that could be defamatory. I assume you must be confident enough to defend your method and data in the court if that scenario plays out.

That said, confidence is irrelevant if it comes to court, what matters is certifications, experience, qualifications and a proper write-up that can stand the scrutiny of experts

.I'm not sure how you came to the conclusion that they're NCR18650BE. We can't both have the same cells, awesome test equipment, and come to drastically different conclusions. Some variable is different...Fun that we have conflicting data...

okashira described his instruments, method and provided a link to some of his results. That notches up his credibility over anyone else that hasn't done that.

....... I mean even though there is lots of data supporting what wk057 has reported in the opening post, we should definitely just assume it is all wrong........

No instrumentation or method provided, hence no validity

 

[kennybobby]

...
No instrumentation or method provided, hence no validity

Not everyone has the time or ability to read and keep up with the rapid pace of wk057's projects and tinkering, but he has described all the instrumentation and methods in various posts while dismantling a couple of tesla battery packs, designing and installing a huge solar array grid on his house, including wiring up all the connections, controllers and other equipment necessary to use the packs to store the solar energy and power-up his house and charge his teslas completely from that system.

And he didn't die of electrical shock or burn down his house or car, and he still has all his fingers and toes.

Oh yeah and in his free time he reverse engineered the CAN busses used by tesla so he could read the actual brick voltages, pack currents, motor torque and power, and all the diagnostic screen info, and described how all that was done in another thread.

Like i said it's difficult to keep up, but he has plenty of validity and credibility amoung the technical crowd. His knowledge, skills and abilities have been demonstrated numerous times--nobody practiced in the art of electrical engineering would doubt his results.

 

[Johan]

Here's another tidbit, real simple stuff, to support the notion that the 85kWh rating is misleading:
Charge fully. Drive at an even pace until you run out of charge. Note the Wh/mile that the car is giving you. Multiply by number of miles driven. You'll be lucky to get even 76.

 

[JRP3]

Flathill clearly has knowledge about the cells and their characteristics, so I value his inputs. Unfortunately his posting style doesn't fit well with this forum and if he can't tone it down a touch is likely to get banned again. (No I don't have the ability to do that nor would I want to, just saying where I see this heading.) Not surprisingly he's clashed with wk who has also suffered banning in the past. It would be nice if we could just stick to data and theory and avoid personal attacks. I'd like to see wk return to this thread and compare data and methods with Okashira and others.

 

[scaesare]

Flathill clearly has knowledge about the cells and their characteristics, so I value his inputs. Unfortunately his posting style doesn't fit well with this forum and if he can't tone it down a touch is likely to get banned again. (No I don't have the ability to do that nor would I want to, just saying where I see this heading.) Not surprisingly he's clashed with wk who has also suffered banning in the past. It would be nice if we could just stick to data and theory and avoid personal attacks. I'd like to see wk return to this thread and compare data and methods with Okashira and others.

Seconded on all points.

 

[tomas]

Here's another tidbit, real simple stuff, to support the notion that the 85kWh rating is misleading:
Charge fully. Drive at an even pace until you run out of charge. Note the Wh/mile that the car is giving you. Multiply by number of miles driven. You'll be lucky to get even 76.

You have to factor in normal degradation. Anyone who did any research bought their tesla knowing there's a capacity drop in first year, then levels off. Anyone who does your simple test who did not do research may not factor in normal degradation or anti brick and get indignant. Bad test.

 

[Cottonwood]

Here is yet another example of "Specsmanship."

In the grow light industry, it is very common to rate LED lights as the sum of the individual LED ratings. For example, an array with 100, 3W LEDs is rated at 300 Watts. The rub comes in the fact that for longevity and to avoid severe heat build up, the LEDs are typically run at half or less of rated power, so a 300 W LED array typically draws less than 150 Watts from the wall. See Galaxyhydro LED Grow Plant Light 300w Greenhouse Indoor Grow Lighting as an example.

That now has gone even further with the new Chip On Board (COB) designs that use a dense array of 64 (8x8) LED chips with a reflector. Because 64x3 or 192 is almost 200, these are rated at 200 Watts per assembly. See High power COB LED Grow Light 800W Panel Flower 64x3W leds - 4*200W as an example.

Specsmanship...

 

[AWDtsla]

Here is yet another example of "Specsmanship."

In the grow light industry, it is very common to rate LED lights as the sum of the individual LED ratings. For example, an array with 100, 3W LEDs is rated at 300 Watts. The rub comes in the fact that for longevity and to avoid severe heat build up, the LEDs are typically run at half or less of rated power, so a 300 W LED array typically draws less than 150 Watts from the wall. See Galaxyhydro LED Grow Plant Light 300w Greenhouse Indoor Grow Lighting as an example.

That now has gone even further with the new Chip On Board (COB) designs that use a dense array of 64 (8x8) LED chips with a reflector. Because 64x3 or 192 is almost 200, these are rated at 200 Watts per assembly. See High power COB LED Grow Light 800W Panel Flower 64x3W leds - 4*200W as an example.

Specsmanship...

Yeah in a commodity market by shady entities. Not when you're Tesla and your nearest competitor already has quarter of the thing you're selling.

 

[Doug_G]

A couple of posts were moved to snippiness

 

[Pajda]

The cells are NCR18650BE, I said this a year ago...
Yes, you can get 11.9Wh out of a cell when new, even close to new.
They are rated at 3200 mAh.

If they are close to NCR18650BE with 3200mAh rated capacity they can't be 11.9Wh. The only cells which are rated as ~12Wh at 3200mAh are LG or Samsung LCO cells with 4,35V charging voltage and 3,75V nominal voltage (I have tested them). But for NCA chemistry you need at least 3300mAh nominal capacity to get close to 12Wh.

Let me get a new cell in my tester, I am sure I will get 11.9Wh out of one. :wink:

I look forward to this test, but I don't expect more than 11,4Wh.

 

[LetsGoFast]

Did you not just read that okashira said the 85kwh rating is correct? He has been testing Model S cells for over a year as have many others. Wk has a vendetta and is in no way a trusted source. Others have claimed he is a day trader. No doubt he is part genius. A boy wonder. This thread has already been picked up my multiple media outlets.

It would be helpful if you could restrain yourself to debating the actual technical points. Your personal assessment of wk's motivations and character is not only unhelpful, it generates noise and reduces my impression of your credibility.

 

[dsm363]

mod note: one post moved to snippiness

 

[JRP3]

If they are close to NCR18650BE with 3200mAh rated capacity they can't be 11.9Wh. The only cells which are rated as ~12Wh at 3200mAh are LG or Samsung LCO cells with 4,35V charging voltage and 3,75V nominal voltage (I have tested them). But for NCA chemistry you need at least 3300mAh nominal capacity to get close to 12Wh.

I look forward to this test, but I don't expect more than 11,4Wh.

Here is one way to get close to 12Wh from them, discharge to 0 volts for a few hours:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=67721#p1022079

 

[okashira]

Well, then it must be true. I mean even though there is lots of data supporting what wk057 has reported in the opening post

Well, it's the lack of data that led me to reply here in the first place.

If one wants to make a technical claim, argument or comparison, they need to provide the data, conditions and peer-review-able technical reporting to back it up.
Too much info is missing in the OP, but from what was said, I can point out the errors and missing information:
-500mA is too high of a current draw to make a Wh capacity determination. A quasistatc discharge rate needs to be used - or in its place a better proxy, such as a pulse discharge or a very slow discharge rate.
-Charge voltage needs to be specified
-Charge cut current needs to be specified
-Discharge cut voltage needs to be specified
-Test temperature needs to be specified
-Kelvin, aka, 2-wire voltage measurement needs to be used.

Reporting also serves another purpose - one should demonstrate they have the technical understanding to even proceed with the experiment, calculations and conclusion they come to. For example, Watts - especially Watt Hours, is not a measurable quantity - it can only be calculated. Thus, one should understand possible sources of error and uncertainty in the measured quantities and how they combine in the final calculation.

Furthermore, Measuring Watts or Watt Hours of a specific period of time of the energy consumed by some device is trivial compared to making a Watt Hour capacity determination of a battery. The second is subject to an order of magnitude of additional variables - such as some of what I specified above. (and it was not a complete list)
Thus - measurement of the energy capacity of battery becomes as much of a matter of opinion (aka - a massive set of conditions need to be agreed upon and standardized) as it is scientific fact. One should point out which variables are subject to opinion and which variables are sources of error in a measurement.

All of the items I pointed out in the list above are sources of actual technical error in the measurement, not the variables that will be subject to opinion - aka - standardization - when making a battery Watt Hour determination. Those will be things such as - acceptable cycle life, calendar life. energy buffer built into the system design, etc.

*off-topic drivel deleted

 

[techmaven]

I greatly appreciate both wk057's and okashira's contributions to this thread and to TMC.

In the end, even if we get data that shows that the technical labeling of the Tesla cells can be accurate, there remains an issue that I think gets to the heart of the matter.

Tesla sold us 85 kWh of cells, but Tesla's 85 kWh pack is really a 81 kWh pack in its intended use. The actual usable amount for driving is even less... at 77-78 kWh. The result still gets the intended range (265 EPA 5 cycle miles) So Tesla wrong here? Now, if the pack is "really" 81, or "really" 85, we have known that the usable amount is 77-78 kWh. I can see both sides of this. There is no standard for labeling here, and it is not uncommon for OEMs to pass along achievable specs, even if that isn't what you can actually achieve (reference my hard drive analogy).

Separately, when they then cooked up the 60 kWh version, they ended up putting in more cells to achieve whatever metrics they wanted and didn't tell us they added extra capacity. For those that are upset that Tesla didn't say so, the 208 EPA miles versus 265 EPA miles is still true. Whether they could achieve that with a 58, 60, 64 kWh pack doesn't change the rated spec. You likely bought based on the rated range spec, not the kWh difference in reality.

 

[Pajda]

Here is one way to get close to 12Wh from them, discharge to 0 volts for a few hours:

https://endless-sphere.com/forums/viewtopic.php?f=14&t=67721#p1022079

Maybe we both read different graphs, but till now I just did not seen any graph where the Tesla cell discharge significantly more than 3100mAh. And if I look on discharge voltage curves I don't see more than 3.6V nominal voltage, so these cells are 11.16Wh at best - exactly as described Wk and you can read from Tesla BMS (díky pupiku :smile: ).

By the way today I have ordered a samples of NCR18650BE and add them to my test schedule.

 

[AWDtsla]

I greatly appreciate both wk057's and okashira's contributions to this thread and to TMC.

In the end, even if we get data that shows that the technical labeling of the Tesla cells can be accurate, there remains an issue that I think gets to the heart of the matter.

Tesla sold us 85 kWh of cells, but Tesla's 85 kWh pack is really a 81 kWh pack in its intended use. The actual usable amount for driving is even less... at 77-78 kWh. The result still gets the intended range (265 EPA 5 cycle miles) So Tesla wrong here? Now, if the pack is "really" 81, or "really" 85, we have known that the usable amount is 77-78 kWh. I can see both sides of this. There is no standard for labeling here, and it is not uncommon for OEMs to pass along achievable specs, even if that isn't what you can actually achieve (reference my hard drive analogy).

Separately, when they then cooked up the 60 kWh version, they ended up putting in more cells to achieve whatever metrics they wanted and didn't tell us they added extra capacity. For those that are upset that Tesla didn't say so, the 208 EPA miles versus 265 EPA miles is still true. Whether they could achieve that with a 58, 60, 64 kWh pack doesn't change the rated spec. You likely bought based on the rated range spec, not the kWh difference in reality.

Right. Even if okashira is right, if I guess at 25kW average highway cruising draw, then I get approximately 1A per cell, plus or minus depending on pack voltage, etc. So even his data says that under normal usage you'll never get 85kWh out of the pack.

...and that still doesn't explain the difference between 60 and 85. Although I don't believe EPA vs EPA is true at all for 70 vs 90.