Calculate usable battery capacity based on rated miles values

[randvegeta]

The value used per rated mile doesn't change. Your driving can effect actual efficiency, obviously. And as pack degrades and you get less rated miles per charge the value per mile is still the same.

You say that but I am going by the 'rated' line on my graph, not by my average.

I am able to drive slower or faster and get my average below or above the rated line. When I drive exactly ON THE LINE, so my average = rated, the number is usually 188wh/km (or 301wh/m). However, I have seen this number climb to 191wh/km (or 306wh/m).

** Sorry, in my previous post, I may have wrongly stated a wh/m of 313, but I was using a conversion of 60M per 100KM rather than 62 **

In either case, my wh/m is higher than you suggested, and certainly is not a static figure.

I may be located in Europe/Lithuania, but the vehicle is a US import. I'm not sure where the 'rated' figure comes from, or weather or not they update the figure to account for location or weather conditions. Certainly I do not find it particularly difficult to meet this estimate unless the road has a good deal of snow/slush on it. Even at -20c, not really difficult to hit that 188-191 range.

Any way, it seems strange that you and others are saying this number is static and is the figure given by the EPA, and yet, my number is neither static, nor matches the number you or others have given.

I'll take a picture next time! Since people seem not to believe me.

 

[randvegeta]

I recall the same 303 Wh/mi value for achieving Rated range on my very early Sig S85 (delivered in September, 2012). I cross-checked the Trip meter's average energy consumption against the Energy graph's 30-mile averager, on several occasions, and it always came in at 303 or 302 Wh/mi when the predicted range remaining lined up with the Rated range remaining. I'll have to dig back through my photos to see if I can document this: I used to be fairly obsessive about taking snapshots of the Energy graph and Trip meters when on road trips.

This higher consumption value (303 vs 295) may have to do with the higher curb weight of early Model S compared to the cars that rolled off the line a year or two later, after Tesla completed a weight reduction program for the S.

Interesting. If I take my 188wh/km and divide that number by 0.620934, I get 302.76969. So within 0.23wh of your rated 303wh/m reading. Mine is an older (2014) model so it may be the case that the original Model S's really had this higher consumption compare to newer ones.

With 191wh/km, that would be 307.6wh/m. Perhaps the graph is not detailed enough to show if a difference of 1.5% is above or below the rated line?

 

[wk057]

The rated line on the graph does not move. The only thing that can potentially make it move a hair is toggling range mode, but that's up in the air.

And again, I'm unsure how this all plays out when converting from other regions or from km or whatever the case may be there. The numbers I provided are directly from the firmware. I don't know what, if any, modifiers are placed on these numbers when in another region, using kilometers vs miles, using range mode, etc.

The value is "VAPI_ratedWattHourPerMile" in the firmware. I've checked it on real cars of various configurations as well as my bench MCU with simulated configurations. The only values that exist are the ones I provided. I suppose at some point I can try configuring a bench MCU for another region and testing again, but it's time consuming to do so. Also, as far as I can tell this is 295 Wh/mi for the RWD variants in every firmware version I have back to 4.x.

 

[ab26]

Oh, right, should probably note that one as well along with the S 90D. I'm unsure the reasons for those particular discrepancies, but likely just a result of all of the rounding involved along the way to these numbers on Tesla's side.

I am interested in knowing more about this (X 75D) as well. It is really odd and I wondering if a rounding error really led to a huge over-estimate (and why we don't see it in the other packs).

 

[randvegeta]

The rated line on the graph does not move. The only thing that can potentially make it move a hair is toggling range mode, but that's up in the air.

And again, I'm unsure how this all plays out when converting from other regions or from km or whatever the case may be there. The numbers I provided are directly from the firmware. I don't know what, if any, modifiers are placed on these numbers when in another region, using kilometers vs miles, using range mode, etc.

The value is "VAPI_ratedWattHourPerMile" in the firmware. I've checked it on real cars of various configurations as well as my bench MCU with simulated configurations. The only values that exist are the ones I provided. I suppose at some point I can try configuring a bench MCU for another region and testing again, but it's time consuming to do so. Also, as far as I can tell this is 295 Wh/mi for the RWD variants in every firmware version I have back to 4.x.

Interesting.

BTW, you wouldn't happen to know if if replacing the charger on a Model S would be a particularly difficult one? I'm thinking it would be best to change my charger to Euro spec one where I can make use of 3-phase charge points.

 

[nwdiver]

Any incite into the calibration issues? Like why my rated range goes up when I'm on a long road trip with several deep cycles... I typically keep my SOC at 60% and my rated range has dropped to ~230 on my P85... I'm hoping that most of that is a calibration issue and not true degradation. That would suck.

 

[Oyvind.H]

Question: This is my 90D. It appears to me that it has 84,9+4kWh=88,9kWh pack size. Is that correct?

 

[Az_Rael]

All RWD Cars (non-Performance and Performance): 295 Wh/Rated Mile

It appears my energy graph is displaying 300 for my wh/rated mile on my classic P85. I wonder if that is just for ease of display?

 

[AWDtsla]

I don't think a cold pack has anything to do with it, I've noticed it each time I've turned on range mode before heading out on a road trip - and this has been at various times of the year (e.g. June, Sept, Oct...).

That said, most instances were sometime in the a.m, after car sitting in the (unheated) garage overnight, since I was leaving on a trip at beginning of the day. but none of those times would have been particularly cold. Likewise every time I've turned off range mode, I've noticed the rated km displayed go down by a few km. I expect if I go out to my car now and turn on range mode without doing anything else, the displayed rated km will go up slightly... (but I won't do that now, it's definitely cold outside right now!)

I just tried this again. 235.59 miles vs 235.25 miles. So decent chance you wouldn't see it without using the API unless you get lucky.

 

[f-stop]

I just tried this again. 235.59 miles vs 235.25 miles. So decent chance you wouldn't see it without using the API unless you get lucky.

in my case the times I noted it was not from the API, it was always on the instrument cluster display. Just checked it again - I just stopped a charging session to 77% - rated range on the dash shows 298km. If I then turn on range mode setting and wait a few seconds, the display changes to 300km. Turn the setting off and it then goes back to 298.

 

[hacer]

The rated line on the graph does not move...

That's true. It also doesn't draw the line where it should. My refreshed 70D for example has the line exactly on 300 Wh/mi. So the line is pretty much useless.

 

[stopcrazypp]

• 85/P85/85D/P85D - ~81.5 kWh total capacity, ~77.5 kWh usable

...

• All RWD Cars (non-Performance and Performance): 295 Wh/Rated Mile

I'm going to play contrarian again, but as a sanity check, by my math, this suggests: 77.5kWh / (295Wh/Rated mile) = 263 miles rated range for a brand new S85 or P85.

This does not jive with data here that says 265-269 (78.2-79.4 kWh usable) is typical when new, while the OP in the thread reported 274 (which works out to 80.83 usable).
Already lost 4 miles of rated range… | Tesla Motors
Another report of 269 miles at new:
Realistic usable energy in 85kWh pack
Another of 271 miles (79.9 kWh) at new:
Degradation at 94.000 miles
Another of 269-271 miles rated when new:
(New Thread) 2012 Model S P85 - Signature Red - WARRANTY - 8K Miles On New Pack
Another of 269 when new:
One Year, 29K Miles, Still Grinning
272 (80.2 kWh) when new:
Decreasing rated range.
273 (80.5 kWh) when new:
Decreasing rated range.

So either your sample of the ~77.5kWh usable (and thus also the ~81.5kWh) is not the typical/maximum number for a new 85kWh battery or your rated mile conversion is off.

 

[LargeHamCollider]

Question: This is my 90D. It appears to me that it has 84,9+4kWh=88,9kWh pack size. Is that correct?

I suspect that the capacity of recent 90 packs is slightly greater than the capacity of the original 90 packs. There were a number of cases where early 90 owners complained of rapid range loss just after buying, you don't see that anymore which also suggests one or more minor chemistry changes *after* the original launch of the 90 pack.

 

[bxr140]

I'm hoping that most of that is a calibration issue and not true degradation. That would suck.

And...is there a way to reset the calibration?

 

[ohmman]

I suspect that the capacity of recent 90 packs is slightly greater than the capacity of the original 90 packs. There were a number of cases where early 90 owners complained of rapid range loss just after buying, you don't see that anymore which also suggests one or more minor chemistry changes *after* the original launch of the 90 pack.

My 10 month old X90D charged to full at 250 rated yesterday. Rated 257 new. My P85 hasn't been charged to full in a long time, but it might be worth checking.

 

[wk057]

I'm going to play contrarian again, but as a sanity check, by my math, this suggests: 77.5kWh / (295Wh/Rated mile) = 263 miles rated range for a brand new S85 or P85.

This does not jive with data here that says 265-269 (78.2-79.4 kWh usable) is typical when new, while the OP in the thread reported 274 (which works out to 80.83 usable).
Already lost 4 miles of rated range… | Tesla Motors
Another report of 269 miles at new:
Realistic usable energy in 85kWh pack
Another of 271 miles (79.9 kWh) at new:
Degradation at 94.000 miles
Another of 269-271 miles rated when new:
(New Thread) 2012 Model S P85 - Signature Red - WARRANTY - 8K Miles On New Pack
Another of 269 when new:
One Year, 29K Miles, Still Grinning
272 (80.2 kWh) when new:
Decreasing rated range.
273 (80.5 kWh) when new:
Decreasing rated range.

So either your sample of the ~77.5kWh usable (and thus also the ~81.5kWh) is not the typical/maximum number for a new 85kWh battery or your rated mile conversion is off.

Again, the rated range Wh numbers are *directly* from the firmware. They're not "my" numbers.

Further, the BMS calibration is WAY off until a near 0% and near 100% charge is hit. It has no data to go on besides the base data, so when it uses it's base numbers and sees a pack taking slightly more energy than expected to reach a particular voltage or discharging slightly more energy than expected before hitting a particular voltage, it celebrates and bumps the cap artificially. Eventually this averages out, especially if you actually use the capacity of the pack. If you're only doing small DoD and never hitting 100% or 0% ... then I personally wouldn't even trust the range meter at all.

With the 85 packs in particular, I've tested cells from what was basically a brand new pack in my testing. I stand by my findings. I would love to see an IC shot of an "85" showing 80 or more kWh used on a single charge.

 

[stopcrazypp]

Again, the rated range Wh numbers are *directly* from the firmware. They're not "my" numbers.

Further, the BMS calibration is WAY off until a near 0% and near 100% charge is hit. It has no data to go on besides the base data, so when it uses it's base numbers and sees a pack taking slightly more energy than expected to reach a particular voltage or discharging slightly more energy than expected before hitting a particular voltage, it celebrates and bumps the cap artificially. Eventually this averages out, especially if you actually use the capacity of the pack. If you're only doing small DoD and never hitting 100% or 0% ... then I personally wouldn't even trust the range meter at all.

With the 85 packs in particular, I've tested cells from what was basically a brand new pack in my testing. I stand by my findings. I would love to see an IC shot of an "85" showing 80 or more kWh used on a single charge.

If what you say is true, the data I gathered suggests that the baseline capacity of a brand new 85kWh pack is much closer to 85kWh than it is to 80kWh.

Also, I mentioned previously that according to Panasonic's own chart, the NCR18650A loses 3.2% capacity vs max nameplate within 5 cycles (note I'm using this as a similar cell example, not saying this is the cell Tesla uses). So if it takes a full 0-100% cycle to get the capacity, by that time it likely would have gone through more than the equivalent of 5 cycles. Then it becomes impossible to know if the stabilized number is representative of a new cell (just the BMS needing to calibrate) or if it's actual capacity loss from the cycling. This also assumes Tesla/Panasonic haven't done any cycling before the car is delivered.
Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

 

[wk057]

If what you say is true, the data I gathered suggests that the baseline capacity of a brand new 85kWh pack is much closer to 85kWh than it is to 80kWh.

Also, I mentioned previously that according to Panasonic's own chart, the NCR18650A loses 3.2% capacity vs max nameplate within 5 cycles (note I'm using this as a similar cell example, not saying this is the cell Tesla uses). So if it takes a full 0-100% cycle to get the capacity, by that time it likely would have gone through more than the equivalent of 5 cycles. Then it becomes impossible to know if the stabilized number is representative of a new cell (just the BMS needing to calibrate) or if it's actual capacity loss from the cycling. This also assumes Tesla/Panasonic haven't done any cycling before the car is delivered.
Tesla's 85 kWh rating needs an asterisk (up to 81 kWh, with up to ~77 kWh usable)

So now we're back to trying to say the 85 packs use cells that are most similar to NCR18650A cells (false) and that Tesla cycles the packs significantly before delivery (pure speculation, likely false as there is no evidence to support this). I'll note again that I've tested "85" pack cells from a pack that still had the majority of its original from-delivery charge with results that match my original findings.

Keep in mind the rated range advertised for the "85"s: 265 miles ... 78.175 kWh usable new.

Also, it's been noted that enabling/disabling range mode modifies the displayed range by some unknown amount. Did you check all of your examples for this particular case? Were these immediately after charging before actually starting the car? The display adjusts to the BMS values within a minute or so of actually enabling the drive rail when the estimated rated range during a charge is way off. I've personally had my old P85 say 272 miles at 100% at a supercharger at ~5k miles on the odo, then snap back to ~263 miles less than 3 miles down the road. In short, the end of charge number means very little, especially before some calibration has happened. Start the car.

And I'll note, again, that this thread is about rated miles vs usable capacity, not cycle life or cell type or whatever. If you want to pick a stance and then cherry pick potentially unrelated data points that support your view, by all means. I'm sure other reasonable persons will realize this and weigh validity accordingly.

 

[wk057]

I suspect that the capacity of recent 90 packs is slightly greater than the capacity of the original 90 packs. There were a number of cases where early 90 owners complained of rapid range loss just after buying, you don't see that anymore which also suggests one or more minor chemistry changes *after* the original launch of the 90 pack.

I suspect this may also be the case. I have data that shows an upward trend in usable capacity that correlates with VIN increases... but, it's not all that significant and could just be error from limited samples. The best 90 packs I've seen are still below 90 kWh in total capacity, including one I own that only has 301 miles on it.

 

[jeffro01]

Stupid question possibly but would I need to fully charge my 90D (pre-refresh) to 100% before I could do this math? I have always felt like I got screwed on paying for the upgrade from 85 to 90 while it was still out there but haven't felt personally wronged by it enough to make a fuss... Now that I see your math, it makes me VERY curious...

Granted at this point with the car over a year old there isn't anything I can do about it now as Tesla, and they aren't wrong, would say that it's due to natural capacity loss...

Oh and despite any previous postings that were defensive of Tesla and aggressive towards Jason, my perspective has changed a lot since then so please Jason, keep doing what you're doing...

Jeff