Rated miles and battery degradation calculation

[ishareit]

How do you guys calculate your full rated miles short of charging the battery completely?

I had my "Trip" meter on (that always shows current battery in percentage) and changed the setting to show the rated miles on the instrument panel. As soon as the percentage changed on my Trip meter, I noted the rated miles on the instrument panel and did the simple math to get total rated miles.

150 miles with 62% battery gives me 241.9 rated miles (150*100/62), about 3% degradation (S75 at 249 rated miles) with only about 680 miles (in 2 weeks) on the car.

Is this a reliable way to get actual battery capacity and degradation? Is my degradation normal?

 

[fasteddie7]

I wouldn’t call it degradation as much as I would call it the results of your driving patterns. The most accurate way I found to determine the type of range I’m getting is to utilize the energy setting in the instrument cluster and check your watt hours per mile. If you are getting 250 wh/m and there’s 1000 wh in a kilowatt hour, you’d get 4 miles per kilowatt hour and you theoretically have 75 of those puppies, 4 x 75 = 300 miles of range. Of course there’s less in my 75 usable, more like 72 and some change, and word on the street is newer 75s might have greater capacity, you can get a rough idea this way. (I use 250 only because the math is easy)

 

[ishareit]

I wouldn’t call it degradation as much as I would call it the results of your driving patterns. The most accurate way I found to determine the type of range I’m getting is to utilize the energy setting in the instrument cluster and check your watt hours per mile. If you are getting 250 wh/m and there’s 1000 wh in a kilowatt hour, you’d get 4 miles per kilowatt hour and you theoretically have 75 of those puppies, 4 x 75 = 300 miles of range. Of course there’s less in my 75 usable, more like 72 and some change, and word on the street is newer 75s might have greater capacity, you can get a rough idea this way. (I use 250 only because the math is easy)

Sorry if I wasn't clear. I meant the "rated miles" which shouldn't change based on how you drive. "rated miles" is the amount of miles advertised by Tesla. For example, for my car, the rated miles on a full charge is supposed to be 249 and if my car shows anything less, that should be considered a battery degradation.

Please correct me if I am wrong.

 

[fasteddie7]

my experience is that this changes with pattern. My 100% can vary from 252 to 259 based on temperature and my last miles driven. This morning my 90% was 226 three days earlier it was 223. Last time I charged to 100% it was 252, the time before 256. I’ve seen time affect it also, I’ve gone to sleep at 90% with 225 and woke up with 223. I think once it hits your set limit, it can lose a few and not start charging again before you take it off charge. Anyone else have a technical explination?

 

[comanchepilot]

Battery degradation is the decrease in charge capacity of the vehicle. Not decrease in miles obtained due to vampire load, warm temps, cool / cold temps etc.

I think you are looking for a number which is impossible to compute except at the end of an ownership experience.

I think what you need to is schedule a trip of 350 miles or so. Loop it through SC's and carefully note temperature, sun angle, inside temp set, weight in the vehicle etc. because if Day 1 is done on a trip with it being sunny out, your car will warm up faster - meaning more AC effort - if its 80F vs. 65F again - different battery chemistry at the different temperatures.

The ONLY way to determine battery degradation is to do the same trip over the same roads in the same traffic and weather condtions and compare it to the same trip 1, 2 or 4/5/6 years later. Then you see what you have left when you stop to charge at each point. The drop from year to year is battery degradation . . .

However, you will see more of a drop on a 85 to 45 degree day that you will see in 8 years. At least thats their hope. . .

 

[Darmie]

Being a new Tesla owner I'm no expert on the topic but I will offer my 2.345 cents. I will first say that there is a LOT of gray matter when it comes to these numbers and what rated miles actually represent (IMHO). Before we received out car, I used the 300wh per mile just to help with the math. Now that we have the car and I dug a little deeper, rated miles is a calculation that comes from the EPA. From here, you will see they use a calculation of 286 watts per mile. Q: What is "Rated Range"? - Tesla Motors Wiki
But, that's a rated range of 265 miles. Now what I found from using TeslaFI since I've owned the car, I believe my s 75 uses approx 275 watts per mile to conform to the rated miles displayed. I'll share some screen captures from teslafi that show the Efficiency of several of my day drives. With a full tank, I also show 243. I mainly documented that as a reference since the car is new. So, If I understand it correctly, if I were to drive and only use approx 276 watts per mile, then I would have the amount of range left on a charge that shows on the screen. I also use the trip tab under the watt meter on main screen to show percentage of charge at arrival. I've also noticed that if you want to be above the line, just slow down. Sometimes hard to do on these fast moving Texas highways though. Hope this helped. I forgot to mention the main reason to take the picture is to see what this number appears to be over time and that I believe will be the degradation on battery performance. Now, only time will tell.

 

[Ugliest1]

To me, since Tesla doesn't give us nearly enough information to accurately measure, getting into huge math is essentially doing precise measurements with a teaspoon but gathering the data with a backhoe. So my backhoe solution is: charge to 100%, what's the rated miles/kilometers. Go have fun for a week or a month or a year. At some point, charge to 100% again, what's the rated distance. Realize that the number will change a little over time, down OR up. Over time, you'll get a vague idea.

Personally, on an almost 4 year old car with 95,000km, the 100% number at new was 425km and now it's anywhere between 406 and 413 -- so, about a 4% degradation. APPROXIMATELY. More tellingly, the first couple of years showed the most decrease; it's been at 406 lowest for two years (i.e. no loss).

Note that Tesla will also occasionally tweak the algorithm they use for Rated Miles/Kilometers, and you won't know when or by how much. So again, I think it's impossible (IMPOSSIBLE, I say! ) to get precise measurements.

 

[ishareit]

Good information, thanks everyone.

If I call their charge state API, I get the following battery miles. The car is currently at 80% SoC

"charging_state": "Complete",
"charge_limit_soc": 80,
"battery_range": 193.44,
"est_battery_range": 199.14,
"ideal_battery_range": 242.2,
"battery_level": 80,
"usable_battery_level": 80,

Anyone knows the difference between battery_range, est_battery_range and ideal_battery_range? Also when will the battery_level not match the usable_battery_level?

 

[jmitchell]

I've been wondering this as well. I have an 85 with almost 70k miles, and at 100% charge the estimated range showed 244 miles. When the car was new did it show the EPA estimated 265 miles, or some other number?

 

[Brass Guy]

Not sure, but most likely:

Battery range is the range displayed with "Range" set at "Rated"
Est battery range is probably range based on some driving history or other conditions.
Ideal range is the range that would be displayed with the "Range" set at "Ideal"

The last one (Ideal) I am very sure of. It has also been speculated here on TMC that Ideal Range has never been altered by Telsa updates, and there are some here that still post their rated range using Ideal for comparison sake.

Note: The "Range" setting is under Units and Format. Rated is supposed to represent driving habits that would achieve EPA range. "Ideal" is possible to achieve driving a constant ~55 mph on level ground with no HVAC and no wind on a nice day.
I think that in other countries the 2 settings are "Rated" and "Typical", where Typical is closer to what people actually get; ie lower than rated, and their "Rated" display is higher than ours due to differing testing procedures.

 

[jmitchell]

Not sure, but most likely:

Battery range is the range displayed with "Range" set at "Rated"
Est battery range is probably range based on some driving history or other conditions.
Ideal range is the range that would be displayed with the "Range" set at "Ideal"

The last one (Ideal) I am very sure of. It has also been speculated here on TMC that Ideal Range has never been altered by Telsa updates, and there are some here that still post their rated range using Ideal for comparison sake.

Note: The "Range" setting is under Units and Format. Rated is supposed to represent driving habits that would achieve EPA range. "Ideal" is possible to achieve driving a constant ~55 mph on level ground with no HVAC and no wind on a nice day.
I think that in other countries the 2 settings are "Rated" and "Typical", where Typical is closer to what people actually get; ie lower than rated, and their "Rated" display is higher than ours due to differing testing procedures.

Thanks for that. I checked and the 244 at 100% was "rated" while "ideal" shows 262 miles at 90% charge.

Does anyone here remember what "rated" number their 85 showed at 100% charge when it was new?

 

[Brass Guy]

Mine read 272 the day I picked it up. Back then, Tesla delivered cars fully charged.

 

[Ugliest1]

Thanks for that. I checked and the 244 at 100% was "rated" while "ideal" shows 262 miles at 90% charge.

Does anyone here remember what "rated" number their 85 showed at 100% charge when it was new?

Jan 2014 pickup S85, 28 km on the odometer, a 100% charge netted 425km or 264mi. Now, almost 4 years and 94,000km later 100% gets 406km (252mi).

 

[tnt1971]

Thanks for that. I checked and the 244 at 100% was "rated" while "ideal" shows 262 miles at 90% charge.

Does anyone here remember what "rated" number their 85 showed at 100% charge when it was new?

It depends on which 85. There was an 85S, 85D, and a P85D. I have the 85D, which had 275 rated miles on its first range charge. After just about 30k miles, it has 272. 244 from 265 is a big drop. I doubt it was that high initially.

 

[Rocky_H]

about 3% degradation (S75 at 249 rated miles) with only about 680 miles (in 2 weeks) on the car.

You have less than 700 miles on your car; you don't have any real degradation yet. What you do have is what all of these cars get within the first few months. The calculating algorithm of the car trying to estimate how much energy is in the battery gets a little bit inaccurate. All of these cars will appear to drop somewhere around 5-10ish miles off of their full charge within the first 6 months or so because of this, but then it usually stays pretty steady for another couple of years. There are a couple of things you can do to get the reading a little closer to accurate, but that's just to give you a warm fuzzy feeling.

 

[jmitchell]

It depends on which 85. There was an 85S, 85D, and a P85D. I have the 85D, which had 275 rated miles on its first range charge. After just about 30k miles, it has 272. 244 from 265 is a big drop. I doubt it was that high initially.

Mine is just an 85. The EPA rated range is 265, but Google shows 253, but I don't know where Google gets the number. If the Google number is accurate then I've only lost about 3.55%, which isn't bad.

 

[Rocky_H]

Mine is just an 85. The EPA rated range is 265, but Google shows 253, but I don't know where Google gets the number. If the Google number is accurate then I've only lost about 3.55%, which isn't bad.

Yes, 265 rated miles was the original value for the S85 and P85, but not the dual motor versions.