Model Y Battery Calibration

[Wennfred]

Hello everyone, I wanted to share this with anyone interested in restoring those lost range miles. May 2020 Build AWD with 19” Gemini wheels.

So this Model Y with 17,385 miles has degraded to 294 miles on 100%

when I first got the car it was rated at 326 but I only would max out at 316 miles at 100% charged.

So a few weeks ago I took a trip to Yuma Az from San Diego, Ca. It’s about 2 hours 45 minute run at around 187 miles. Starting miles was 294.

Since that trip I have ran the battery down to 5% and most times 8-9% to the full 100%

I kept doing this and saw the range increasing, it would stay at 302 for a few cycles and then get to 306 and then stay at 308 for 3 cycles and this last time I charged at 20 Amps to 100% and it took me back to 310 a miles, that’s all I wanted to see.

The reason for this excessive battery calibration and I think I did this like 11 times, not the 3 or 4 cycles was that tomorrow I head out on a road trip to Tennessee and from there to Key West, Tampa, New Orleans and back home. Here are some pictures of today’s results.

Fred

 

[jcanoe]

Thank you for sharing your results. After 10+ full charge to deep discharge cycles of the Tesla's battery your Tesla now displays 5% more range than if you had just driven the Tesla, charged as you had been doing for the past year. If you are traveling cross country and presumably using the Supercharger network would you ever be in a situation where the additional 5% (16 miles) of estimated range would make a difference? I would plan on stopping to charge at a Supercharger every 2 to 3 hours (at most) so the additional range would not be a factor.

 

[sgalla04]

Thank you for sharing your results. After 10+ full charge to deep discharge cycles of the Tesla's battery your Tesla now displays 5% more range than if you had just driven the Tesla, charged as you had been doing for the past year. If you are traveling cross country and presumably using the Supercharger network would you ever be in a situation where the additional 5% (16 miles) of estimated range would make a difference? I would plan on stopping to charge at a Supercharger every 2 to 3 hours (at most) so the additional range would not be a factor.

I'm curious to know if this "increase in range" is really true or just a visual calculation. Specifically, let's say true 100% is 320 miles and it is showing 290. Are you able to theoretically still travel the 320 even though it shows 290? I realize you aren't going to bring it down to 0% and in real life you can expect lower than the estimate, but curious to know if you are actually gaining true range or just showing a more accurate expected range. Because if the entire time the car is still able to drive 320 miles, then calibrating it isn't too important. But I get it, for road trips then it will better calculate distances and % to next supercharger. So I do see a benefit.

Does anyone know if their car is actually able to drive further post a calibration or is it just a visual estimate improvement?

 

[silverstoned83]

I'm curious to know if this "increase in range" is really true or just a visual calculation. Specifically, let's say true 100% is 320 miles and it is showing 290. Are you able to theoretically still travel the 320 even though it shows 290? I realize you aren't going to bring it down to 0% and in real life you can expect lower than the estimate, but curious to know if you are actually gaining true range or just showing a more accurate expected range. Because if the entire time the car is still able to drive 320 miles, then calibrating it isn't too important. But I get it, for road trips then it will better calculate distances and % to next supercharger. So I do see a benefit.

Does anyone know if their car is actually able to drive further post a calibration or is it just a visual estimate improvement?

Yes, you can* travel further than what is displayed.. because this is not dependent on whether or not the BMS sees the available capacity. In fact, there was an article that was recently posted about this particular subject, which I think was on electrek.co.

Unlike a ICE's gas tank, an EV's battery capacity is very difficult to measure.. even for the BMS. In the end, the max potential range is dependent on the available battery capacity, which can only be accurately measured by going on a +300 mile road trip in one go. You then use the Wh/mi and distance traveled (GPS) results, while factoring in the percent error in distance traveled that the vehicle believes it traveled, to do the math and reveal the available capacity. Being that you are often unable to discharge down to 0%, you can add the remaining charge on top of the measured capacity from 100% down to wherever you had to end the test.

In the end, the accuracy of the calibration does not impact the distance that the MY is able to travel, the only control you have over that is with your right foot.

 

[mark95476]

This is a great data point for fellow owners!

You've put on a lot of miles in the past year and your battery degradation is almost nil.

It's pretty amazing that the best way to maintain your Tesla's battery is to use it constantly fully.

Thanks for sharing.

Hello everyone, I wanted to share this with anyone interested in restoring those lost range miles. May 2020 Build AWD with 19” Gemini wheels.

So this Model Y with 17,385 miles has degraded to 294 miles on 100%

when I first got the car it was rated at 326 but I only would max out at 316 miles at 100% charged.

So a few weeks ago I took a trip to Yuma Az from San Diego, Ca. It’s about 2 hours 45 minute run at around 187 miles. Starting miles was 294.

Since that trip I have ran the battery down to 5% and most times 8-9% to the full 100%

I kept doing this and saw the range increasing, it would stay at 302 for a few cycles and then get to 306 and then stay at 308 for 3 cycles and this last time I charged at 20 Amps to 100% and it took me back to 310 a miles, that’s all I wanted to see.

The reason for this excessive battery calibration and I think I did this like 11 times, not the 3 or 4 cycles was that tomorrow I head out on a road trip to Tennessee and from there to Key West, Tampa, New Orleans and back home. Here are some pictures of today’s results.

View attachment 663686

View attachment 663687
View attachment 663688

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Fred

 

[MY-Y]

It's a bit ironic that the way to show the least degradation is to deep charge to 100% many times - which accelerates degradation.

 

[silverstoned83]

It's a bit ironic that the way to show the least degradation is to deep charge to 100% many times - which accelerates degradation.

There's nothing ironic about it from my perspective. You're helping the BMS see the capacity that was invisible to it by demonstrating that there is in fact available capacity beyond what it was estimating.

 

[pho35]

Hmm gotta try this approach. I've tried a few even the one suggested by Service (discharge to 20% and charge to 100% 3 times) but none help. I'm in the same boat in terms of range, bought it for almost a year and I'm floating at 293mi at 100%.

 

[rjpjnk]

I doubt this exercise is changing battery capacity. Most likely it is just calibrating the estimator.

 

[Y Not]

will try this too. I also tried the recommended solution by Service and I'm still capped at a displayed range of 258 miles at 100% for my MYP.

 

[Ruffles]

Did you wait for the car to sleep at those low battery states? I've started trying to recalibrate the BMS and am seeing improvements but I'm just curious about your process.

 

[TomServo]

I doubt this exercise is changing battery capacity. Most likely it is just calibrating the estimator.

I believe this is the case. I wish EV’s could figure out a way to display something that doesn’t trigger these concerns.

 

[Darmie]

Good to hear. I guess the key is to drop it below 10 percent down to 5 percent. Not sure if I want to do that to far from home charger though.

I just let TeslaFI figure it out and not worry about it. I'm usually in Percentage mode anyway.

 

[steve841]

This should be automated by Tesla software....

Seems to me that if 100% = 310 miles / 80% = 260 miles, etc .. . the BMS should compensate or adjust to those corresponding numbers ... of course degradation would have to be accounted for. Which Tesla should have ample data to incorporate.

 

[laughMan]

our MY has only 4400 miles, but max out at only 304 miles at 100%.
I read about the BMS reset procedure, but doesn’t it also hurt the battery life by draining and full charging the battery??
what cause the range to increase after the BMS reset?? if it is a SW calibration error, shouldn’t tesla fix it by software upgrade???

 

[TomServo]

This calibration stuff reminds me of a saying my father was fond of saying decades ago - "Figures don't lie, but liars figure".

What I want to know is HOW MUCH energy (kWh) was available in my battery when NEW and NOW. The exact or even expected number of miles you can get from that energy is really unknown, or a GUESS at best. There are too many variables to calculate to any degree of accuracy.

Give me those two numbers and I can figure out the rest. So I guess we need to buy the SMT gizmo to know this.

 

[rjpjnk]

What I want to know is HOW MUCH energy (kWh) was available in my battery when NEW and NOW. The exact or even expected number of miles you can get from that energy is really unknown, or a GUESS at best.

Correct. All that matters is how much energy the battery can hold (capacity). The rest is just blipiddy blip, but it is so much fun to talk about it seems to go on and on...

 

[Rocky_H]

I read about the BMS reset procedure, but doesn’t it also hurt the battery life by draining and full charging the battery??

Yes it does, which is why all of this trying to "tune in" the BMS estimation algorithm is not doing anything beneficial for the battery. It is entirely just about making uptight anal retentive people get a warm fuzzy feeling that the number appears more "right".

what cause the range to increase after the BMS reset??

Thing1: Trying to read the amount of energy in a battery has always been a challenging and complicated endeavor. It is not at all like measuring sugar in a measuring cup or spoon, where you can look right at it, or scrape it flat across the top to see exactly how much is there. It doesn't work like that.

Thing2: So the battery estimation systems have to look for certain signs, like voltage levels, along with trying to measure and track how much energy is going into and out of the battery.

Thing3: With some battery types, like Ni-cad, they have a more noticeable slope of reducing voltage as they are running "low". But with lithium ion batteries, they have a very flat voltage level throughout most of their middle range. That is a benefit for a lot of uses, but makes them hard to read their fullness. The battery reading systems never get to see much voltage change if they are not getting to the low or high end to mark that as an end point, so the estimates drift.
As an interesting side example of this, I get the low battery warning from my Xbox controller when using the Ni-cad rechargeable AA batteries, but not with the lithium ones that just shut off with no warning, because they are managed to stop output before they get to that lower point where the voltage drops off really fast.

if it is a SW calibration error, shouldn’t tesla fix it by software upgrade???

Ha! Uh, they have been doing that for 15+ years! They have a very good estimation algorithm, but it can only work from the information it is being given. And if you never let it see a high or low point with a different voltage, you are not giving it enough information to work with to measure it accurately. Lack of information in its use cases is not something that can be "fixed" by a software upgrade.

I was just commenting about this in another thread last week. New owners are always wanting these two things at the same time, which just can't happen, because they are opposite, conflicting goals.

Treat the battery the nicest.
Have the most accurate battery reading.

You don't get to have both at the same time. The healthiest thing for the battery is small charge/discharge cycles in the middle of the state of charge. But that is also what is giving the least information for the car to read the state of the amount of energy in the battery, so the estimate is going to get fuzzy.

 

[TomServo]

I found this several months ago and just plugged in my numbers as the car sits after 13 months and 9K miles.

The results came to 71.14 kWh

How accurate is this? Is that saying I'm able to pull 71.14 kWh from my battery when new it was about 72.5 kWh? So essentially I have almost NO degradation even though the BMS is reporting I have 294 miles of range?

 

[MY-Y]

The energy screen approach gives the BMS kWh estimate. I've used the scanmytesla app to directly read the capacity, and it agrees with the energy screen math (within a couple of tenths). The max range also gives this same number.

For me, this number dances all over the place. If I do my normal routine of charging from ~60% to 80% each day, my reported capacity drops to ~67.5 kWh 1-(67.5/77.8)=14% "degradation." The average for the 100 similar cars in teslafi is 8%.

Not thrilled with this number, I've tried various tricks to "calibrate" the BMS. As far as I can tell, only one of the discussed techniques works. Charge to 100% (for me, that includes the >2kWh added in the hour after my car reads 100%) and then drive it down pretty far (~20%). This can be over several trips / days. Let the car sleep when not driving for this charge cycle.

Unfortunately, this "calibration" is very short lived.
July 1, range = 282, 2 cal trick cycles... July 12, range = 291.7.
August 8, range dropped to 288, 100% to 5% cal trick, range = 295.8. Almost average.
3 weeks later, range = 282.79.

Lessons learned:
1. True degradation is hard to know.
2. The BMS error is fixed mainly by charging for an hour past 100% to add the energy that the BMS didn't think the battery could hold.
3. Daily use, and every trip I take aren't impacted by degradation at all.
4. Paying close attention to "degradation" only reduces how much I enjoy the car, with no upside.
5. The best approach is to not pay attention to this, and not bother with the "calibration" unless you are selling the car.