juliusa
Active Member
Yes - if your SOC% suddenly drops by 4-6 percentage points there is something wrong. Time for a service appointment.
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I think my car is lying to me...
- Thread starter supratachophobia
- Start date
I didn't see this thread three weeks ago, but I'm surprised no one appears to have mentioned that the EPA rating for the car in kWh per hundred miles includes charging losses.
They measure power pulled from the wall and miles until the car stops, not anything about how much power ends up in the battery (which would be challenging to get in a standardized fashion.)
When the car gives you watt hours per mile in the trip computer or energy screens, that's power from the battery during the time the car is on, so they aren't comparable. (My EPA rating for my X75D is 36 kWh per hundred miles, but the car appears to use around 308 Wh per mile for rated range - implying about 15% losses/overhead.)
They measure power pulled from the wall and miles until the car stops, not anything about how much power ends up in the battery (which would be challenging to get in a standardized fashion.)
When the car gives you watt hours per mile in the trip computer or energy screens, that's power from the battery during the time the car is on, so they aren't comparable. (My EPA rating for my X75D is 36 kWh per hundred miles, but the car appears to use around 308 Wh per mile for rated range - implying about 15% losses/overhead.)
Brando
Active Member
It is a battery.
Battery is in no way = to a gallon of petrol.
Temperature (for example) changes the battery. Take the same measurement at different temperatures and the number WILL be different.
Tesla "manages" some of this temperature changes with a "cooling system" for the batteries.
Get used to it. Stop looking for some precis value - close enough is close enough.
You never knew exactly how many pints in your fuel tank - you won't know exactly how much energy in your battery. Just make sure you have enough. That is why you just plug it in when ever you are parked at home.
Battery is in no way = to a gallon of petrol.
Temperature (for example) changes the battery. Take the same measurement at different temperatures and the number WILL be different.
Tesla "manages" some of this temperature changes with a "cooling system" for the batteries.
Get used to it. Stop looking for some precis value - close enough is close enough.
You never knew exactly how many pints in your fuel tank - you won't know exactly how much energy in your battery. Just make sure you have enough. That is why you just plug it in when ever you are parked at home.
I'm not saying the canbus values are misreported, I am saying that what they actually are representing may be misunderstood, since only Tesla knows what they mean. That's why I asked you about your nominal full pack value reading.
Nominal value divided by EPA consumption is the exact number listed for rated range. When the battery gets below 20% on a long trip, the car begins to use the usable value divided by EPA consumption. It's really not a misunderstanding, the car is giving you information based on one value, then on a completely different value. And it refreshes on it's own, hoping the driver won't notice.
I agree there is something strange going on, but I don't think the 290 Wh/mi number is from the EPA. I think the only numbers that come from EPA is rated range and kWh/100 miles, the later which includes charging and other internal battery losses. I think Tesla uses that 290 number but it doesn't match actual performance. In my car, I consume rated miles at 270 Wh/mi, regardless of what percent charge my battery is reading. I never achieve rated miles at 290 Wh/mi. But when I charge my battery, it charges at close to 290 Wh/mi.
In any case, I think only Tesla could explain what is really going on, but they might not want to.
@wk057 confirmed the watts per mile used for each EPA calculation for each model. I think some people are confused about Tesla "changing" the algorithm. They can improve the estimation and the prediction of the battery degradation and the "remaining" range can be adjusted based on weather conditions for trip estimation. But they can't just change the EPA rated watts per mile to lie to the customer.
If my car actually displayed ~250 miles on a full 100% charge, then we wouldn't be in this thread. But if it did say that, then I'd be barking at Tesla that 15% range degredation is completely unacceptable for a 2.5yr old car.
I don't think @wko57 claimed that number came from the EPA. He showed that it is used by Tesla, not that it comes from the EPA, or used in any EPA calculation. The only EPA spec numbers I have seen are rated range and kWh/100 miles. EPA doesn't give any Wh/mi number, at least I've never seen it.
Also, if you were at 294 rated miles when new, and now are at 272 rated miles, that is 7.5 % degradation.
I must be missing something, isn't Wh/mile just kWh/100 miles multiplied by 10?
Edit: ah, I see from a couple posts earlier you call out that that includes charging losses.
You item D may be incorrect.
The 2015 S90D was EPA rated at 340 Wh/mile (34kWh/100 miles)
Gas Mileage of 2015 Vehicles by Tesla
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Interesting that 340 watts per mile is the EPA number. And if that's the case, then where can they possibly get the other numbers from?
My hang up is this: Whichever way you slice it, Nominal or Usable, you get two numbers. And only one of those numbers faces the owner; the other is never seen anywhere. Assuming that consumption you listed is right, here are all the variations based on 290 and 340 w/m:
New (based on wk057 research)
85.8 nominal brand new
290 w/m = 294 miles (this was actually advertised, correct?)
340 w/m = 249 miles
81.8 usable brand new
290 w/m = 282 miles (wasn't there some advertising that the 90 was 6% better than the 85kwh?)
340 w/m = 240 miles
Brand New Observed After 1 Month
290 miles
84.1kwh (nominal)
80.1kwh (usable)
Now
78.9 nominal
290 w/m = 272 miles (this is the number I see on the dash)
340 w/m = 232 miles
74.9 usable
290 w/m = 258 miles
340 w/m = 220 miles
Ah, 294 was for the 2016 S90D. EPA calls out a range of 270 miles for the 2015 S90D , but they may not have actually tested it per Official EPA Ratings For Refreshed Tesla Model S - 90D Range Is 303.2 Miles Highway
Not sure what Tesla called out, way back machine is being slllooowwww....
I believe the early 90 pack was a chemistry altered 85, whereas the later 90 was a software limited 100 pack. I think early 90s were also the ones that started limiting DC charge rates after some number of cycles.
I have never heard this before, do you have any links to back that up?
Well I'm batting .500
The 85 kWh to 90 kWh shift:
Charged EVs | Tesla tweaks its battery chemistry: a closer look at silicon anode development
But the 90 was never a SW limited 100, Tesla did have an upgrade option for vehicles pre-delivery.
Rereading the article I linked, the change in EPA range may have been due to being an extrapolation from the 85 kWh pack initially. Also says Tesla rated it at 288 Mile range originally.
Just to further my point, if you look at wk057's data on the original P85, he claims that a 85kwh battery was actually 81.5 nominal and 77.5 usable. If you use the 295 wh/mile that was used for coming up with the EPA tests, 77.5kwh gets you 262 miles of EPA range. So obviously Tesla started out using a number very close to, or exactly, the usable capacity when reporting back to the owner. Because, you know, that's called telling the truth. What we need to find out now, and what I'm working on, is are all cars using the algorithm of rated range based on nominal, or do some use usable.
Brando
Active Member
I wish you guys would go test other EV makers and tell us all who is better at "telling the driver the truth" so we can all cancel our Tesla orders and reward the truth tellers with our dollars/orders. That will get Tesla's attention and end all these lies.
Now, just one last thing. How do I use this "truth" to improve my BEV ownership experience exactly?
PS- ..."8 year or unlimited miles Battery and Drive Unit Limited Warranty."....
Vehicle Warranty | Model S and Model X
who else matches the above Tesla warranty??
PPS- how much money will I save over 5 years not buying gasoline? please don't lie.
PPPS - what other cars have fast chargers = to Tesla SuperChargers? which others are faster? I'm tired of wasting time at SuperChargers.
PPPPS- when will Tesla only use solar power for it's chargers? and who will do it before Tesla?
</sarcasm>
Now, just one last thing. How do I use this "truth" to improve my BEV ownership experience exactly?
PS- ..."8 year or unlimited miles Battery and Drive Unit Limited Warranty."....
Vehicle Warranty | Model S and Model X
who else matches the above Tesla warranty??
PPS- how much money will I save over 5 years not buying gasoline? please don't lie.
PPPS - what other cars have fast chargers = to Tesla SuperChargers? which others are faster? I'm tired of wasting time at SuperChargers.
PPPPS- when will Tesla only use solar power for it's chargers? and who will do it before Tesla?
</sarcasm
>
I have a totally uninformed question to ask about all this, as I'm not following this very well. How do we know what the car's battery is able to do? I thought you cannot know the battery capacity while using it.
Aren't all of the number coming from the car just current estimates? The car is guessing how far it thinks you will get based on the battery charge and how you drive the last x miles. If I drive my car like a bat out of hell, uphill, against the wind, my numbers will suck, go the other direction, it's super. Aren't your range number always in flux. MY car only has about 11k miles and it's settling into around 280 wh/mile.
Not trying to cause and issue, just trying to catch up to the concern of battery degradation. We just have to make sure we are getting good numbers... right?
Aren't all of the number coming from the car just current estimates? The car is guessing how far it thinks you will get based on the battery charge and how you drive the last x miles. If I drive my car like a bat out of hell, uphill, against the wind, my numbers will suck, go the other direction, it's super. Aren't your range number always in flux. MY car only has about 11k miles and it's settling into around 280 wh/mile.
Not trying to cause and issue, just trying to catch up to the concern of battery degradation. We just have to make sure we are getting good numbers... right?
Here is what I think is happening and is probably consistent with at least some of what you have observed:
1) The full rated range is determined by dividing the nominal kwh by .290 (.295 for the original 85). In your case, 84.1/.290 = 290 rated miles.
2) The consumption of rated miles is determined by the usable value, in your case 80.1/290 miles = 276 wh/mi in order to achieve rated miles
This also works with your current degraded battery:
78.9/.290 = 272 rated miles
74.9/272 miles = 275 wh/mi in order to achieve rated miles, virtually the same as original case
It's interesting to note that the way wk057 calculates usable matches what the canbus calls the nominal value.
Unlike almost all the other manufacturers, Tesla isn't using history and guessing range based on it for the instrument panel display. The only history based estimate you get on a Tesla is the average of last xx miles one in the center console energy app.
Instead, the Tesla instrument panel offers two choices that are both based on a fixed watt hour per mile number (though different numbers in different car models.) Ideal is some best case scenario, Rated is supposed to match EPA rated range/test cycle.
There is still estimation error, because as you said, the car has to use an alogorithm to guess the chemical state of the battery most of the time due to the flat voltage curve of lithium creeks and the effects of pushing power in and out of the pack on voltage, but it should be a much smaller factor.
I have about a 2 million row CSV file I'm working on right now that tracks and entire discharge cycle from 100% to 5%.
Highlights: total mileage driven was 222 @ 314 wh/mile. If you assume that for the last 3.9kwh (5.2%) I would have driven at the same consumption, I would gone an additional 12 miles. 12+222 is 234 miles....
Usable capacity is 75kwh on the nose when full. 75kwh at 314 wh/mile is 238 (257 miles @ 290 wh/mile). 4 mile vampire drain over the course of the day seems fair.
SO... all that to say, it ends up being 12.9% battery degradation over 2.5 yrs and 64k miles. Seems a bit much to me....
Last fun fact; % remaining appears to be using USABLE CAPACITY.
Last last fun fact, the BMS seems to get super optimistic when the battery is low. At 5%, it estimated the full rated range at 288 miles.
Highlights: total mileage driven was 222 @ 314 wh/mile. If you assume that for the last 3.9kwh (5.2%) I would have driven at the same consumption, I would gone an additional 12 miles. 12+222 is 234 miles....
Usable capacity is 75kwh on the nose when full. 75kwh at 314 wh/mile is 238 (257 miles @ 290 wh/mile). 4 mile vampire drain over the course of the day seems fair.
SO... all that to say, it ends up being 12.9% battery degradation over 2.5 yrs and 64k miles. Seems a bit much to me....
Last fun fact; % remaining appears to be using USABLE CAPACITY.
Last last fun fact, the BMS seems to get super optimistic when the battery is low. At 5%, it estimated the full rated range at 288 miles.
Not sure how you are processing, but for big data sets I change the CSV into binary and use Python+matplotlib for graphing. Runs faster, especially on loading.