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

DJRas

Member
May 9, 2017
646
2,988
Victorville, CA
I re-did my test yesterday one one non-stop drive from 100% charge down to zero (excluding the anti-bricking buffer). Actual zero is impossible, but I had to dead-stick it into the Sheetz parking lot and push it into a Supercharger stall. It wouldn’t go into any gear.

This time it showed 71.8 kWh used in the 240.3 mile trip at 299 Wh/mi (slightly more efficient than the 310 rated for a P85D).

If 85 packs originally had 77.5 useable, then I am down 5.7 from new, or 7.3%. Which doesn’t seem all that good for a pack with only 28K miles.

Battery voltages at 100% charged (five minutes after unplugging with charge complete):
View attachment 427345

Battery voltages at empty:
View attachment 427344

Dashboard with trip info:
View attachment 427342

Maximum rate seen during Supercharging:
View attachment 427343

It seemed it took about 5 minutes after plugging the Supercharger cable in before the car started charging. Group 57 appeared to be about 55 Mac less than any other cell groups. I hope I didn’t damage anything, but isn’t that what the bottom-end buffer is for?
Your data shows pretty good degradation. The TMSpy data also shows that they use the "Nominal" fullpack (includes the 4kWh buffer). Their SoC is the nominal remaining divided bybthe nominal full pack. This when you were at or near zero percent usable TMSpy shows 5+%.

My car prior to 2019.16.1.1 update had similar degradation (about 8%). But now my rated range is 217 miles and Usable full pack of 60.3kWh (23%).

The original 2014 S85 battery was advertised with EPA rated range of 265 miles at 295Wh/mile. That comes out to a usable 78kWh originally usable.

At some point Tesla also change the multiplier used to calculate the rated range displayed on our dashboard. The current multiplier is 276Wh/mile.
I don't have enough data the pinpoint when thst occurred.
 

Blu Zap

Grinning member
Oct 1, 2014
1,094
739
San Rafael, CA.
But now my rated range is 217 miles and Usable full pack of 60.3kWh (23%).
That's what I am seeing Full pack is around 60 kWh. I started with a full topped off battery. Finished with 7% remaining having used 58.1 kWh. So lets forget about miles and talk about kWh. It seems like 2019.16.2 reduced kWh. It had been at about 5% degradation previously. Or 73.15 kWh. Now around 60.0 kWh. So about an 18% loss in kWh thanks to 2019.16.2. Sound right?
 

DJRas

Member
May 9, 2017
646
2,988
Victorville, CA
That's what I am seeing Full pack is around 60 kWh. I started with a full topped off battery. Finished with 7% remaining having used 58.1 kWh. So lets forget about miles and talk about kWh. It seems like 2019.16.2 reduced kWh. It had been at about 5% degradation previously. Or 73.15 kWh. Now around 60.0 kWh. So about an 18% loss in kWh thanks to 2019.16.2. Sound right?
My estimate is 8kWh loss with 2019.16 2.
247×0.276=68.2 kWh... now 60.3
 
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tomas

Out of warranty...
Supporting Member
Oct 22, 2012
4,326
4,247
Santa Barbara/New York
Important to keep the 16.2 discussion in 16.2 thread. Why?

1) not everyone affected. My P85 totally unaffected. Keeping it together helps with the sleuth work to figure out how to know if you are affected.

2) volume of owners (not posts) in that thread influences Tesla to prioritize fix. Shotgun discussion at bottom of years old thread does nothing.

3) this thread is about delivered hardware capacity. Degradation (real, imagined) and software induced reductions of usable capacity (intentional/permanent or accidental/temporary) are another topic.
 
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I re-did my test yesterday one one non-stop drive from 100% charge down to zero (excluding the anti-bricking buffer). Actual zero is impossible, but I had to dead-stick it into the Sheetz parking lot and push it into a Supercharger stall. It wouldn’t go into any gear.

This time it showed 71.8 kWh used in the 240.3 mile trip at 299 Wh/mi (slightly more efficient than the 310 rated for a P85D).

If 85 packs originally had 77.5 useable, then I am down 5.7 from new, or 7.3%. Which doesn’t seem all that good for a pack with only 28K miles.

Battery voltages at 100% charged (five minutes after unplugging with charge complete):
View attachment 427345

Battery voltages at empty:
View attachment 427344

Dashboard with trip info:
View attachment 427342

Maximum rate seen during Supercharging:
View attachment 427343

It seemed it took about 5 minutes after plugging the Supercharger cable in before the car started charging. Group 57 appeared to be about 55 Mac less than any other cell groups. I hope I didn’t damage anything, but isn’t that what the bottom-end buffer is for?

Very good details!
Looking both a TM-Spy and your dashboard, the car's BMS 'believes' you have as much as 5% left even if the car is 'unwilling' to use it...possibly because of Group 57 that is out-lyingly low.

Your 7.3% degradation includes this remaining 5% energy in the battery (which is NOT the brick protection).
Possibly in ideal conditions and after some magical BMS balancing event, that 5% (or part of it) could become usable again and thus your 'true' degradation would be significantly less than 7.3%...if I'm trying to stay positive.

Negatively speaking, if it is group 57 that is creating a large portion of your degradation, you may be experiencing further range decrease if this group continues trending down!!!...in which case, maybe you'll be 'lucky' enough to hit Tesla's warranty threashold..
This graph helps highlighting that Group 57 is an outlier within Tesla's pack and although they don't recognize this data officially, it gives good leverage in your discussions with them if it stays out-of-whack compared with the rest.
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,528
1,728
Pennsylvania, USA
As for the myth about driving the battery to under 10% SOC and AC charging back to 100% to rebalance the cells, over the last week or so I did just that.

First discharged to 5% SOC, overnight 40A charge to 100%, then down to 4% and back to 100%, then down to 2% and back to 96% where the charger shut off well before reaching 100%.

The Pack kWh as reported by TM-Spy was 77.3 at the first complete charge, 76.9 at the second, and down to 73.9 at the third!
9D8DBDDA-4C15-42E2-9F4B-F8E2B000F69B.jpeg


At this point, I thought I was damaging my pack from multiple charges to 100% despite driving the car within ten minutes or so of completing the charge.

After I got to work, my Pack was back to 78.2 kWh.
9888EB75-0D96-4041-AC96-89B411707F73.jpeg


Basically I have no clue where the Pack number is coming from or how it is calculated. My latest charge (40A to 80%) now shows 77.0 kWh.
EA1B0B46-303F-42E3-8DF0-4D67EFFFDCD7.jpeg


Judging by my voltages at my latest charge to 100% (1st image), if I am being limited, it is more of a barbershop shave than a scalping. I won’t be charging to 100% again for quite a while.

At low SOC, my “57” group still shows a good bit lower than the rest.

So basically I have no idea what the software is doing to my pack.
 
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Worth an update here.

Tesla has changed the balancing algorithm many many times over the years. Originally this was a very dumb setup that would only kick in once a cell group reached a threshold voltage, usually around 90-93% SoC. This is no longer the case.

First, let me point out that Tesla's BMS software has come a LONG way... I'd consider it a work of art now. Lots of genius in there. It's absolutely amazing and full kudos where kudos are due here.

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 car balances all the time whenever its needed. It knows when a cell group will need balancing before it's even out of balance... which is really freaking weird when you think about it, especially if you're watching a playback of the pack balancing and voltages and see it engage a balancer on a cell group that doesn't look out of balance at all, and watch it fall completely in line still at the end of a charge or discharge cycle. It keeps track of which groups will need it, which wont, how long they'll need it, how much they've been balanced, etc.

It really is an epic setup now.

The short answer to the balancing question: It balances any time it needs to balance.

As for SoC shenanigans, yes getting closer to 100% or 0% will give it a chance to tune things better... but it's not needed anymore. Just charge like you need to, and drive.


Really fantastic post; clearly indicates use of simultaneous extended kalman filters for prediction of individual 'brick SoC', which enables adaptive balancing.

I'm more impressed that the BMS algorithms are so drastically revised via an OTA update!
 
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EvanLin

Member
Oct 9, 2016
115
158
Asia
Thanks wk057 providing so much information for years. I like these discussions. Just sharing what I saw.

If you could actually get 75 kWh out of a 3 pack, I'd expect dozens or more independent examples all over this forum, YouTube, etc... not just one Tesla fanboy.
An update for this topic.

There are several Scan My Tesla pictures showing 76-79 kWh nominal in recent months. Here is one below.

BTW, does anyone know a good thread/explanation about why energy used in trip meter never came close with nominal kWh, even with driving from 100% to 0% nonstop as Bjorn did?

77kWh.jpg
 
Last edited:

wk057

Vendor & Senior Tinkerer
Feb 23, 2014
5,784
12,601
Hickory, NC, USA
Thanks wk057 providing so much information for years. I like these discussions. Just sharing what I saw.


An update for this topic.

There are several Scan My Tesla pictures showing 76-79 kWh nominal in recent months. Here is one below.

BTW, does anyone know a good thread/explanation about why energy used in trip meter never came close with nominal kWh, even with driving from 100% to 0% nonstop as Bjorn did?

View attachment 543204

Those are just values reported by the BMS, which unfortunately for the Model 3 packs are solely for our benefit. Those particular values are not used by anything in the car, and only people reading CAN data will see them. They don't tend to match values reported by the BMS debug interface.

In any case, my original statement still stands. 100% to 0% drive showing more than 75 kWh consumed on the since-last-charge panel... preferably with a full video (no hilly regen shenanigans).
 

apacheguy

S Sig #255
Oct 21, 2012
5,111
1,305
So Cal
Those are just values reported by the BMS, which unfortunately for the Model 3 packs are solely for our benefit. Those particular values are not used by anything in the car, and only people reading CAN data will see them. They don't tend to match values reported by the BMS debug interface.

Interesting. So are you saying that the CAN message for nominal pack capacity does not match what is displayed in developer mode? If so, then this would seem to imply that we are not reading the right CAN message or it is not decoded properly.
 

MarcG

Active Member
Oct 29, 2014
3,962
5,644
San Francisco
Also, given the fact that most Model 3 LR batteries are closer to 78kWh when new, and given rapid degradation early on, the chances that a new Model 3 owner does 100% to 0% drive nonstop to hopefully see the 75 kWh since last charge is very rare.

I find that most new owners of EVs (which is what most Model 3 owners are) to be initially conservative and shy away from driving the car down to 0%.

That being said, given a lucky new M3 owner that gets 79kWh nominal pack when new, if adventurous enough, it could conceivably be possible to use slightly over 75kWh on a 100% to 0% continuous drive.

The buffer is about 4.5% of nominal pack, so on 79kWh nominal that’s 75.445kWh useable. Of course, the dumbed down Tesla UI does not show decimals, so you would only see 75 kWh, which makes @wk057 correct when stating you may never see over 75kWh displayed in the since-last-charge screen.
 

supratachophobia

Active Member
Sep 24, 2014
3,858
2,759
Columbus, Ohio
Thanks wk057 providing so much information for years. I like these discussions. Just sharing what I saw.


An update for this topic.

There are several Scan My Tesla pictures showing 76-79 kWh nominal in recent months. Here is one below.

BTW, does anyone know a good thread/explanation about why energy used in trip meter never came close with nominal kWh, even with driving from 100% to 0% nonstop as Bjorn did?

View attachment 543204
Because the car doesnt calculate using nominal at the end, it switches to usable as the energy approaches zero. Zero miles on the dash = 4kw remaining for nominal remaining capacity.
 

wk057

Vendor & Senior Tinkerer
Feb 23, 2014
5,784
12,601
Hickory, NC, USA
Also, given the fact that most Model 3 LR batteries are closer to 78kWh when new, and given rapid degradation early on, the chances that a new Model 3 owner does 100% to 0% drive nonstop to hopefully see the 75 kWh since last charge is very rare.

I find that most new owners of EVs (which is what most Model 3 owners are) to be initially conservative and shy away from driving the car down to 0%.

That being said, given a lucky new M3 owner that gets 79kWh nominal pack when new, if adventurous enough, it could conceivably be possible to use slightly over 75kWh on a 100% to 0% continuous drive.

The buffer is about 4.5% of nominal pack, so on 79kWh nominal that’s 75.445kWh useable. Of course, the dumbed down Tesla UI does not show decimals, so you would only see 75 kWh, which makes @wk057 correct when stating you may never see over 75kWh displayed in the since-last-charge screen.

The 78/79 numbers are imaginary. They're the result of incomplete calibration to the real pack, combined with the fudge data in the 3 BMS. The "rapid degradation" at first isn't degradation at all.

(To be clear, the reasoning behind why the CAN-reported values don't match reality may not be, and likely isn't, nefarious... my guess, based on what I can tell from my RE work, is that they just didn't care if those values were accurate since they weren't used by the vehicle... internally, there are more accurate values that aren't reported on CAN and require active polling to retrieve.)
 

MarcG

Active Member
Oct 29, 2014
3,962
5,644
San Francisco
The 78/79 numbers are imaginary. They're the result of incomplete calibration to the real pack, combined with the fudge data in the 3 BMS. The "rapid degradation" at first isn't degradation at all.

(To be clear, the reasoning behind why the CAN-reported values don't match reality may not be, and likely isn't, nefarious... my guess, based on what I can tell from my RE work, is that they just didn't care if those values were accurate since they weren't used by the vehicle... internally, there are more accurate values that aren't reported on CAN and require active polling to retrieve.)

Interesting, so the values reported by CAN that state original full nominal pack of 77.8kWh is all bogus? I've seen that number several times from different owners, so I'm wondering why it's consistently reported across different cars.
 

BigNick

Infamous Fat Sweaty Guy
Dec 3, 2017
1,528
1,728
Pennsylvania, USA
As EVs become more mainstream, savvy customers may demand more transparency into what is going on inside the battery pack. But savvy customers who are willing to pay for a full reporting package will still be outnumbered by those who don’t want to think about the details and just drive it.
Still, even cheap ICE cars usually have a tach on the dash these days.
 

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