Range Loss Over Time, What Can Be Expected, Efficiency, How to Maintain Battery Health

[MarcG]

I didn't have deg when I started, and I haven't had any still. Anywhere from 308 to 312 miles. Can't say why, just luck, probably.

You did get lucky, but that’s most likely because you got a battery with a significant amount of energy more than the equation that corresponds to your EPA range gives for battery capacity. (You probably also have lower degradation rates than most, but you do have battery degradation nonetheless).

It works like this: the displayed range in our cars is calculated by dividing the battery capacity the BMS reports by a constant for the model type. For example, if your BMS reports 75 kWh and your model’s EPA constant is 240 Wh/mi (or 0.24 kWh/mi), your rated range is 75/0.24 = 312 miles.

However, all cars are shipped with batteries that have varying capacities. So to avoid complaints from new owners, Tesla added a logic to the calculation that caps the displayed range to the EPA rated range for each model.

Say your model is supposed to get 310 miles when new: in the example above, this corresponds to 310 * 0.24 = 74.4 kWh. However, most cars will ship with at least 75 kWh when new, which should technically show 312 miles, but Tesla chooses to display 310 instead. So even if the battery loses 0.6 kWh, the rated range will show zero degradation when in fact it has already started happening.

So for those who get lucky and get a battery pack with, say, 77 kWh (321 rated miles, if using the sample constant above), they will appear to have no perceived degradation by just observing rated miles until over 2.6 kWh (or 11 miles equivalent) have actually been lost.

Of course, using a CAN bus reader such as Scan My Tesla will show this is not true, as it is possible to read the nominal full pack remaining that the BMS reports via CAN.

 

[KenC]

Thanks for all of that. I suppose we should say "visible" deg, since there's hidden deg, as you point out. Most questions are about that "visible" deg, so its just simpler to talk about that.

 

[MarcG]

Thanks for all of that. I suppose we should say "visible" deg, since there's hidden deg, as you point out. Most questions are about that "visible" deg, so its just simpler to talk about that.

Sure, it's just less indicative of a battery's true degradation. Keeping track of only "visible" deg makes it harder to compare apples to apples because each battery has a different starting point (capacity).

I've been keeping track of my car's reported rated range when charging completes (see first graph below) since I bought it about a year ago, but only recently got a CAN bus setup to read actual BMS reported capacity values.

You can clearly see the lack of perceived degradation in the first few months, during which my car appeared to always have about 310 miles worth of range, but you can bet your house on the fact that there was clearly degradation during that time.

The second graph shows the equivalent capacity in kWh over time (I have similar graphs over odometer, for those interested in geeking out over data). My guess is that my battery pack actually started around 78kWh total capacity, and steadily degraded until about late last year. It has been relatively stable since, though I definitely do expect more deg over time.

 

[ran349]

Sure, it's just less indicative of a battery's true degradation. Keeping track of only "visible" deg makes it harder to compare apples to apples because each battery has a different starting point (capacity).

I've been keeping track of my car's reported rated range when charging completes (see first graph below) since I bought it about a year ago, but only recently got a CAN bus setup to read actual BMS reported capacity values.

You can clearly see the lack of perceived degradation in the first few months, during which my car appeared to always have about 310 miles worth of range, but you can bet your house on the fact that there was clearly degradation during that time.

The second graph shows the equivalent capacity in kWh over time (I have similar graphs over odometer, for those interested in geeking out over data). My guess is that my battery pack actually started around 78kWh total capacity, and steadily degraded until about late last year. It has been relatively stable since, though I definitely do expect more deg over time.

So, if the BMS was doing what you claim, capping the actual capacity at 310 miles, when you had originally 78 kWh of energy, or about 318 miles of actual range, then if you were charged to 100% you should have driven approximately 8 miles before you saw any miles tick off from the battery icon at 310 miles.

Did you ever observe anything like that?

 

[MarcG]

So, if the BMS was doing what you claim, capping the actual capacity at 310 miles, when you had originally 78 kWh of energy, or about 318 miles of actual range, then if you were charged to 100% you should have driven approximately 8 miles before you saw any miles tick off from the battery icon at 310 miles.

Did you ever observe anything like that?

No. The displayed range drops at a different rate. More elegantly explained in this thread:

Performance not getting 310 miles promised

The charging constant can be used to provide quick predictions of full pack energy - any partial charge and if you use that constant you have to make adjustments if you want to predict current available energy (it’s a slope + offset formula).

My belief explained elsewhere is this is not a cap in the strict sense - just a cap on the displayed value - they inflate every mile instead until the capacity drops below a certain value. There’s not a hidden “buffer” of energy above 310 miles for example - I think when the car is new and very energetic, each mile just contains more energy. And over time that comes down to a fixed value with no change in miles. Then miles start disappearing.

 

[ran349]

No. The displayed range drops at a different rate. More elegantly explained in this thread:

Performance not getting 310 miles promised

Okay, I am familiar with that thread. I thought you were describing something a little different with regard to the capping.

As @AlanSubie4Life said (my bolding):

My belief explained elsewhere is this is not a cap in the strict sense - just a cap on the displayed value - they inflate every mile instead until the capacity drops below a certain value. There’s not a hidden “buffer” of energy above 310 miles for example - I think when the car is new and very energetic, each mile just contains more energy. And over time that comes down to a fixed value with no change in miles. Then miles start disappearing.

In that case, what I described( a delay in rated miles changing) would not happen.

 

[MarcG]

Okay, I am familiar with that thread. I thought you were describing something a little different with regard to the capping.

As @AlanSubie4Life said (my bolding):


In that case, what I described( a delay in rated miles changing) would not happen.

Yep, I agree with you. And sorry I wasn’t clear earlier.

 

[flyin' low]

Sep 2018 M3P is my car. After 41k miles, I get 258 miles at 90% charge. 18" wheels, no mods. A couple of months ago, full charge stopped at 296 miles. Winters here in PNW I lose 30-40% on top of the miles I've driven. I haven't gotten a full charge to 310 miles ever and even after some of the updates, I never got to 325 (I didn't care for that much).
Any advice/tips to charge in any way to really test the battery out? TIA.

 

[SleeperService]

Sep 2018 M3P is my car. After 41k miles, I get 258 miles at 90% charge. 18" wheels, no mods. A couple of months ago, full charge stopped at 296 miles. Winters here in PNW I lose 30-40% on top of the miles I've driven. I haven't gotten a full charge to 310 miles ever and even after some of the updates, I never got to 325 (I didn't care for that much).
Any advice/tips to charge in any way to really test the battery out? TIA.

Same configuration and age as my car. A few more miles (I'm just under 37k miles). What's your daily drive and charging routine? For reference (at least prior to the pandemic lockdown) mine is generally 36 miles on the interstate in the morning at 80+ mph, at work for ~9 hours [open parking lot], 36 miles at 80+ mph home, at that point the battery level is between 50 and 60% depending on whether it's winter or summer, scheduled departure charge to 90%, rinse and repeat. Right now I've got 272 miles at 90% charge. Since the lockdown the car has been sitting in the garage, plugged in, with the charge set at 50%.

 

[flyin' low]

Same configuration and age as my car. A few more miles (I'm just under 37k miles). What's your daily drive and charging routine? For reference (at least prior to the pandemic lockdown) mine is generally 36 miles on the interstate in the morning at 80+ mph, at work for ~9 hours [open parking lot], 36 miles at 80+ mph home, at that point the battery level is between 50 and 60% depending on whether it's winter or summer, scheduled departure charge to 90%, rinse and repeat. Right now I've got 272 miles at 90% charge. Since the lockdown the car has been sitting in the garage, plugged in, with the charge set at 50%.

Thanks for your reply.
I charge daily as I drive 100 miles to work 4 times a week at about 70-80 mph mostly. I clock about 2000-2500 miles a month. AC on at 1 all the time. I used to charge to 80% until a month or so ago and I pushed it to 90%. When parked at work (8-9 hours), I lose about 2-3 miles range. Since the temps have increased a bit, the wh/m has also improved. So I don't think the usage is erroneous; I'm just bummed that the 90 and 100% charge miles have dropped significantly. I guess the battery warranty is 120k miles or 6 years. I will be taking the car into the service center when distancing guidelines ease up a bit.

 

[FlMikey]

Sure, it's just less indicative of a battery's true degradation. Keeping track of only "visible" deg makes it harder to compare apples to apples because each battery has a different starting point (capacity).

I've been keeping track of my car's reported rated range when charging completes (see first graph below) since I bought it about a year ago, but only recently got a CAN bus setup to read actual BMS reported capacity values.

You can clearly see the lack of perceived degradation in the first few months, during which my car appeared to always have about 310 miles worth of range, but you can bet your house on the fact that there was clearly degradation during that time.

The second graph shows the equivalent capacity in kWh over time (I have similar graphs over odometer, for those interested in geeking out over data). My guess is that my battery pack actually started around 78kWh total capacity, and steadily degraded until about late last year. It has been relatively stable since, though I definitely do expect more deg over time.

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I'm pretty new to EV's, Tesla and the M3 so still ramping up and forgive me if this is a daft observation. If I understand your chart correctly, after 1 year it looks like you had a 3.23% loss of range (310 -> 300). Is that 3.23% supposed to remain constant through the life of the car? I hope not as that would mean that after 10 years, the car would have a range of 223 miles approximately (coming from 310), so about 28% loss?

 

[VT_EE]

I'm pretty new to EV's, Tesla and the M3 so still ramping up and forgive me if this is a daft observation. If I understand your chart correctly, after 1 year it looks like you had a 3.23% loss of range (310 -> 300). Is that 3.23% supposed to remain constant through the life of the car? I hope not as that would mean that after 10 years, the car would have a range of 223 miles approximately (coming from 310), so about 28% loss?

Based on most of the old Model S vehicles out there, you'll have more range loss the first year than in subsequent years. Having said that, you are driving a car using a Li ion battery (same as your phone). Do not expect it to last forever. 10 years is a long time and some people have unrealistic assumptions on longevity. Most 10 year old ICE cars with 200k miles are either dead or on their way out.

 

[mrgoogle]

It’s a lottery. Our model 3 is missing -11% capacity from the start (SR+) Tesla can’t help me and sais everything is fine.

 

[Atari2600]

I just looked into my drop, which isn't that bad, but it started just before 18,000 miles and I was on the same software version when the drop occurred so it wasn't that. I was on 2019.28.2 when the slide started. I have been pretty stable 10,000 miles and many firmware versions later.

My graph is from TeslaFi and I am using the beta fleet compare graph.

 

[Jason_G]

It’s a lottery. Our model 3 is missing -11% capacity from the start (SR+) Tesla can’t help me and sais everything is fine.

I have a 9/18 P3 build, and mine only shows ability to charge to 282 miles of rated range instead of 310. I am also seeing ~10-12% effective loss in capacity, and have been since receiving.

 

[KenC]

Just an update to show how 3rd-party apps like Stats, and I believe TeslaFi, use the SOC api that is temperature-dependent. Here's my latest Rated Range data from Stats exported into Excel, with temperature data overlaid. Temp in red, Rated Range in blue. The polynomial best-fit curves are almost identical. The sharp drops in blue, are the blue snowflake days. When I do the math manually, Rated Range divided by SOC, I get anywhere from 308 to 312 miles, even on the coldest Winter days.

I really wish they'd use the non-temp-dependent SOC API, since what 3rd party apps like Stats show, isn't just battery deg and BMS drift, but also seasonal temperature effects.

My chart starts in winter, Jan 2019, where Rated Range seems to average 303miles, then when Summer hits, it's 310miles then as Winter returns, it dropped to 304miles, then now that it's warmed up, it's about 308miles and continuing its upward climb.

 

[Am12345]

I have the Model 3 SR (not plus), so I have an EPA of 220 miles- and what I’ve looked up online-50kwh battery. I picked it up in March, and I have noticed I’m not getting anywhere near the EPA (or whats stated when charged to 100% - 219miles)

I read somewhere charging it to 100% once might help and ‘reset’ the battery, so I did that two days ago. I traveled 141 miles and it ran me down to 12%. Details from the car provide I’m doing 229 Wh/mi and used 32kWh....doesn’t seem right that I came down to 12% at those stats. I used sentry mode for 2 hours.

 

[pl8dlikafiddle]

I have the Model 3 SR (not plus), so I have an EPA of 220 miles- and what I’ve looked up online-50kwh battery. I picked it up in March, and I have noticed I’m not getting anywhere near the EPA (or whats stated when charged to 100% - 219miles)

I read somewhere charging it to 100% once might help and ‘reset’ the battery, so I did that two days ago. I traveled 141 miles and it ran me down to 12%. Details from the car provide I’m doing 229 Wh/mi and used 32kWh....doesn’t seem right that I came down to 12% at those stats. I used sentry mode for 2 hours.

There are idle/vampire losses associated with the car sitting, and in addition, the use of Sentry Mode also adds to the "non-metered" losses that is not accounted for in the 32 kWh that the car is reporting it used.

Also keep in mind there's a bottom and top buffer to protect the battery - roughly 4-4.5%.

On the bright side, your 219mi 100% charge is doing better than my SR+ with 16,000miles. My SR+ is currently hovering between 215-218 miles of rated range.

 

[KenC]

I have the Model 3 SR (not plus), so I have an EPA of 220 miles- and what I’ve looked up online-50kwh battery. I picked it up in March, and I have noticed I’m not getting anywhere near the EPA (or whats stated when charged to 100% - 219miles)

I read somewhere charging it to 100% once might help and ‘reset’ the battery, so I did that two days ago. I traveled 141 miles and it ran me down to 12%. Details from the car provide I’m doing 229 Wh/mi and used 32kWh....doesn’t seem right that I came down to 12% at those stats. I used sentry mode for 2 hours.

Your driving usage was 32kWh. Your non-driving usage was 12kWh. If you leave Sentry and Climate Protection on, you could easily lose over 1 mile of range per hour. In two days, you could potentially lose 50+ miles of range. Is that 12kWh worth or range? It could be.

 

[nimbuzz]

Hey guys, No offense intended but are there any real battery engineers here? I am not but I have been driving EVs for 15 years and have read a lot. Tesla may have cutting edge-state-of-the-art tech that makes my past observations obsolete (?) As I understand it; it is a challenge for the computer to calculate exact range/SOC of a battery especially while sitting--under load is somewhat easier.

Variable 1--Somebody just now = page 56 brought up seasonal temperatures affecting 100% calculations.
Variable 2--I think even Tesla confirmed the standard technique of now and then draining a pack then charging to 100% to recalibrate the battery and the SOC computer.

If these two things are true they could explain some of our discrepancies--no?

2018 M3 Dual