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

vgrinshpun

Supporting Member
Apr 5, 2013
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upload_2019-4-22_0-46-0.png
 
  • Disagree
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wk057

Senior Tinkerer
Feb 23, 2014
5,656
11,388
Hickory, NC, USA

I'm serious.

And 89 kWh into the charger!? That's idiotic. Even with their DC side numbers that'd be only 87% efficient. The full system efficiency of the gen1 model S is better than that even on a bad day. The Model 3 charger is way better, > 90% efficient, and as high as about 94% in testing.

These. Are. Not. Measured. Values. They. Are. *calculated* (poorly). based. On. Other. Data.

Head? Let me introduce you to Wall. Wall? Let me introduce you to Head.
 

vgrinshpun

Supporting Member
Apr 5, 2013
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Yellow shaded areas on the above document are test measurements.

The data you showed here does not match data produced by professional labs. Your conclusion is that everything that does NOT come from you is BS. That makes perfect sense. Reminds me about this joke:

A senior citizen was driving down the freeway when his wife called his cell phone.

"Herman, I just heard on the news that there's a car going the wrong way on Route 280. Please be careful!"

"It's not just one car," said Herman, "It's hundreds of them!"
 

wk057

Senior Tinkerer
Feb 23, 2014
5,656
11,388
Hickory, NC, USA
Since you're not willing to put anything at stake in defense of your position, how about this:

Post the following:

Photo of a "since last charge" on a 3 that comes anywhere close to the 78 kWh number. (This doesn't exist. photoshops or rooted cars don't count...) (edit: looked through my photos... best I've got is 66... so 12 kWh buffer?! Hahahaha)

Anywhere Tesla even claims more than 74 kWh capacity. (Spoiler: internal documentation specifically states capacity is 74 kWh and "may be rounded to 75 kWh for marketing", although they never did this for now-obvious reasons).


Btw, I suggest you at least purchase and read that SAE document before you get that foot of yours much deeper into your mouth. More spoilers: you're reading the data wrong AND those numbers don't come from where you think they do.
 
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David99

Active Member
Jan 31, 2014
4,850
7,021
Brea, Orange County
Worth an update here.
....

Thanks so much about the info regarding balancing. That explains a lot and matches what I see. I keep an eye on balancing and regardless of what I do or how I charge, it always stays in balance amazingly well. Even after 206k miles and 5 years there is only a 3-4 mV difference (when it's charged 90% or more). At lower the state of charge the difference is usually a little more.
 

wk057

Senior Tinkerer
Feb 23, 2014
5,656
11,388
Hickory, NC, USA
Thanks so much about the info regarding balancing. That explains a lot and matches what I see. I keep an eye on balancing and regardless of what I do or how I charge, it always stays in balance amazingly well. Even after 206k miles and 5 years there is only a 3-4 mV difference (when it's charged 90% or more). At lower the state of charge the difference is usually a little more.

Yeah, the small deltas get very exaggerated/magnified at low SoC, and a bit at high SoC.
 
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Alketi

Member
May 3, 2016
875
2,432
U.S.
Since you're not willing to put anything at stake in defense of your position, how about this:

Post the following:

Photo of a "since last charge" on a 3 that comes anywhere close to the 78 kWh number. (This doesn't exist. photoshops or rooted cars don't count...) (edit: looked through my photos... best I've got is 66... so 12 kWh buffer?! Hahahaha)
75kWh. On Ben Sullins vehicle. You can apologize to @vgrinshpun now.

 

erthquake

Active Member
Mar 16, 2016
1,191
3,511
California
75kWh. On Ben Sullins vehicle. You can apologize to @vgrinshpun now.


I was just thinking of that video. And since it’s the LR RWD 3, Ben would have been able to use even more than 75kWh if Tesla has unlocked the extra 15 miles of range that they now have. Plus it was also quite cold then, as far as southwest climate goes. Ben was wearing a pretty thick coat. Is the energy used to warm up the battery at the beginning of the drive counted in the energy usage meter?
 

vgrinshpun

Supporting Member
Apr 5, 2013
5,886
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I was just thinking of that video. And since it’s the LR RWD 3, Ben would have been able to use even more than 75kWh if Tesla has unlocked the extra 15 miles of range that they now have. Plus it was also quite cold then, as far as southwest climate goes. Ben was wearing a pretty thick coat. Is the energy used to warm up the battery at the beginning of the drive counted in the energy usage meter?

So here we go, 78 kWh @wk057 was looking for. 15 miles of range in M3 is equivalent to more than 3 kWh of energy, assuming that Tesla unlocked additional battery capacity with the update. Looks like evidence on this is not solid, but even if no additional battery capacity was unlocked, something is off with the data reported by @wk057, as he claimed that TOTAL model 3 LR battery capacity is 74 kWh, which would mean that usable capacity is lower - i.e. 72 -73 kWh. Per the Ben video, the usable capacity on his car at that point in time was at least 3 - 2 kWh higher.

I believe that energy used to warm the battery while the car is moving is reflected on the energy usage meter.

It should be also noted that the fact that this energy (75 kWh) was pulled out of the battery when it was cold means that total energy that is possible to extract from the battery was slightly lower than if it would be warmer. In my car (MS P85+ circa 2013) I see more than 1kWh difference between capacity reported in winter vs. summer.
 
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wk057

Senior Tinkerer
Feb 23, 2014
5,656
11,388
Hickory, NC, USA
Oh good lord.

I'm... I'm just not going to bother. I'll let someone else with a brain explain why/how that guy got that number.

And this is why I stopped posting here.

Edit: I guess it's my own fault, since I figured people actually would use a legit more controlled and real world example. I guess I'll have to post a video/screenshot ,one day if I ever get time, of 100 kWh+ discharged on an unmodified model 3. Heck, I'll do it with a short range. Hint: it's easier to do this in winter.

Edit: Since it's been buried by fanboys already, post with facts from the horse's mouth (ie, Tesla's own software): Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)
 
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Yeah, the small deltas get very exaggerated/magnified at low SoC, and a bit at high SoC.

For those of us with 85 packs -- who aren't electrical engineers -- can @wk057 give us the layman version of the data?

Specifically, I've been concerned about a few stories of pre-AP 85s displaying miles above zero, some as high as 20ish, and dropping dead with no warning. I've adjusted my trip computing to increase my buffer accordingly, but obviously that affects range, charging time, etc. How is that explained with regards to the "kludge" buffer, etc.?

After nearly 5 years, I've noticed that the last few times I've attempted to full charge (or did successfully) the car would initially estimate something like "5 minutes remaining" then revert to a simple "charging" status FOR HOURS afterwards, while continuing to draw current.

My assumption has been that years of daily drives between 60-80% just threw off the algorithm and therefore my car's rated range would be reported inaccurately. This gives me some peace of mind re: degradation at the top (oh, it's reading lower than new because it's just off) but also less peace of mind regarding degradation at the bottom (oh, it says 40 miles remaining but it might go dark at 20 and surprise me).

If it's rebalancing/calibrating constantly.... then how trustworthy is the reported state of the battery at the top/bottom?

Don't need to get buried in the electrical details, just need an user's understanding of what my car is telling me (or not). Thanks!

I'd posted some screenshots of the charging behavior here: Tesla Pittsburgh on Twitter
And here: Tesla Pittsburgh on Twitter
 

zdriver

Member
Jul 18, 2016
415
2,563
WI
Is the energy used to warm up the battery at the beginning of the drive counted in the energy usage meter?

IIRC from winter driving, it is. But that only happens when the pack is really cold. Like below freezing.
One thing to note is from my experience, power used for HVAC when not in "Drive", is not counted. So if you sit parked with the heat (or A/C) on, that power is not accounted for in the "since last plugged in" number.
 

AWDtsla

Active Member
Mar 3, 2013
4,262
3,952
NE
I have done a lot of data logging and noticed in my 2014 Model S 85, the point at which it switches to constant voltage charging is always just under 90%.

The switchover point seems to be entirely dependent on cell temperature, where max performance is somewhere past 40C. I gather from anecdotal information that the 90's need an even higher temperature than the 85's.
 

AWDtsla

Active Member
Mar 3, 2013
4,262
3,952
NE
One thing they're now able to do is to calculate out the capacity of individual bricks of cells (96 in the 85/90/100, 84 in the rest) based on a ton of factors and compute this in near real time, in a full range of conditions, with almost magical accuracy. They're basically running physics simulations (similar to how they calculate out unmeasurable metrics in the inverter firmware, like rotor temperature) of the entire pack based on measured power usage/charge, balancer usage, temperature, temperature delta based on coolant flow and coolant temp, predicting temperature gradients, and probably 100 more variables. This is the holy grail of proper balancing for safety and longevity for a battery pack. This is not a dumb system anymore by any means. Knowing the actual capacity of the individual bricks allows them to know exactly which ones need cell bleeders enabled, and for exactly how long. With this data, they can balance on the fly at any SoC, and just use top and bottom SoC windows for fine tuning, validation, and calibration.

The estimate I'm getting (2019.12 cb68c3d) is all over the place. Checking canbus total usable capacity, it bounces between ~79.5kWh and ~80.5kWh, however let's say the car is sitting at 70% SoC, it can randomly drop reported in rated miles by ~10 miles over the course of about 3 hours, while the usable capacity only dropped by 1kWh as above. It will readjust of the course of the next few days/drives and gain the 10 miles back. Repeat after a day after the next charge.

Without a canbus reader and teslafi logging I'd be completely in the dark, and think that vampire drain was 10+ miles in one day. I'm still unable to find the math that makes a 1kWh drop in total capacity equal to a 3kWh drop in current capacity at 70% SoC.
 

wdolson

Well-Known Member
Jul 24, 2015
7,451
9,946
Clark Co, WA
@wk057 to change the subject a bit. I recall somewhere in one of your teardown discussions, you mentioned that you thought there was enough space in the S/X packs for the 2170s with some modification to the module height (and internal layout of course to accommodate the different diameter). Did I dream that or was that your conclusion?
 

vgrinshpun

Supporting Member
Apr 5, 2013
5,886
22,789
PA
Asked the friend at Tesla who leaked a bunch of stuff to me about this, and he said "Just post it"...

So, here's a screenshot of an internal document on the Model 3 battery.

m3batsheetss.jpg


Now seriously. Just stop trying to argue this.

This is just preposterous. You always manage to turn any attempt at serious adult discussion into a farce.

Since when an outdated (where is MR?) general descriptive materials somehow override official test results submitted by Tesla to State and Federal government agencies (CARB and EPA)? These are the latest data from Tesla 1/28/2019 filing.

Here is the summary, pertinent pages and link to actual test data of a physical battery pack. Pertinent test data are highlighted for clarity.

upload_2019-4-22_23-25-4.png



TESLA DATA SHEETS WITH TEST RESULTS:

https://iaspub.epa.gov/otaqpub/display_file.jsp?docid=46584&flag=1

upload_2019-4-22_23-5-1.png

upload_2019-4-22_23-5-43.png


upload_2019-4-22_23-6-13.png
 

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vgrinshpun

Supporting Member
Apr 5, 2013
5,886
22,789
PA
Hey @DavidB what are you disagreeing with?

You clicked "disagree" within the seconds of me posting, so obviously did not even look at data. So what is exactly do you find to disagree? Documents filed by Tesla containing official data sheets?
 
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