How I Recovered Half of my Battery's Lost Capacity

[Bad Dolphin]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

Hey WattBeatsGas—

We, too, are of the reluctant senior set. But my wife has always, and still does, like muscle cars, so she’s quite happy with her AWD Model 3! Like your wife, she found the car at first inhibiting due to unfamiliar controls. But with time, we have learned its idiosyncrasies. (Every ICE car has them, too!)

For your bug on the windshield where the heck is the wiper control challenge, there still is a wand control for that. A quick touch to the end of the left control stem gives you one wipe, great for driving in mist. A longer press gives you windshield washer spray and one swipe.

Basically, spend more time with your manual and you’ll find all sorts of things you can do without going deep into menus while driving!

And now, back to the GREAT battery estimation fine tune thread!

Sincerely,
Bad Dolphin


I own a Model 3 and drive it only infrequently ... especially now during the Covid-19 crimp on places to go. Now I'm sure all you young'uns out there will puzzle over how I could possibly lose some sharpness in my senior years; after all, you (and I, too, when I was a young'un) are bright, quick on your feet, sharp memory, and all the rest of the admirable characteristics of not-old humans, AND YOU'LL NEVER GIVE IN TO THE RAVAGES OF AGE, EITHER. Am I not right?

The Tesla autos have sometimes been called, with pride, "a computer on wheels." However, when I describe my M3 that way to others, it's with an inward groan. Why? It is so difficult to do anything, even simple things like open the glove box. In all the ICE cars I've ever driven, it's been easy. A/C? Sure, just reach over WITHOUT HAVING TO TAKE MY EYES OFF THE ROAD and make the adjustments by touch. No way to do that in my computer on wheels.

(btw, I fully expect there will be many crash descriptions of seniors taking their eyes off the road too long and crashing into some innocent car, guard rail at the edge of a cliff, or oncoming fully loaded semi.)

Or, say you want to flip on the windshield wipers to wash off a bug flattened right in your line of vision. If you’re like me, you’ll have to pull over to the side of the road and browse through the logical decision tree on the touch screen (that saves a lot of weight, I’m sure) before you can home in, minutes later, on the part of the algorithm that gives you several choices for windshield wiper activation.

This retired aerospace engineer, who helped design the control system of the GPS satellite decades ago, longs for the simplicity of an old ICE car! Same for my wife, who refuses to drive the M3 because it is “Too complicated.”

Elon! Here’s a demographic that you might not reach until you design a simple ecar: The really senior cohort that really doesn’t need 0 – 60 in 3 seconds. (I tried to think of a name for a senior-appropriate Tesla that could be added to the S3XY lineup, but I nodded off. Maybe after my nap.)

 

[Pricedm]

A/C? Sure, just reach over WITHOUT HAVING TO TAKE MY EYES OFF THE ROAD and make the adjustments by touch. No way to do that in my computer on wheels.

Use voice command! Right button on the steering wheel. Just yesterday, in a rain storm, I activated voice control and said "turn on rear defroster." Ta-da, it's on. PS-- my 3 likes a "please" at the end of each command

 

[2Old2Bold]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

Dear WattBeatsGas,

I get it! I am getting ready to enter my 7th decade. My woodworking partner who is 15 years my senior inspired me to get serious, give up my old convertible ICE car and get a Model 3 Long range. He was an early adopter and is on his 3rd S.

Like all of us, old habits are hard to break. That said I spent a lot of time in the first month of ownership to get all the setting just the way I like them. That's how I got over my learning curve. This minimizes, 'while driving changes' which makes my life, and 'No Name's' (that's what I call my TM 3) better.

Now I will NEVER go back to an ICE car. My wife gets a bit upset when go someplace in her Subaru, get to destination, I get out and walk away while the car is still running. heh heh, that's how much the Model 3 has retrained me

Now to the point of this article...
- Bought the M3 in Nov 2018, have about 20,000 miles on it. Generally run it down to about 20% before charging at home.
- Charge every other week or so, sometimes longer in between.
- Took 3 round trips to RI about 1,400 miles, charge to 100% before leaving, use the Super Charger network on route.
- My daily commute to woodshop is about 2 miles. Occasional 100 ish mile local trips once a month or so.
- Sentry mode is normally on except when parked at home

I have not seen much degradation at all, about 10 miles / 3% loss life to date. Maybe it is my retired lifestyle or Irish luck, but I am happy with battery behavior thus far,

Thanks for listening

 

[Wennfred]

Like many others, I have been concerned with loss of 100% indicated battery range on one of my Model 3s. My P3D (build date 9/13/2018, delivery date 10/8/2018) had gotten down to 270.3 miles at 100% charge on January 20, 2020, at about 30,700 miles, which is a loss of 40.8 miles since the car was new.

I posted about going to the service center to talk with them about battery degradation, which I did on March 9, 2020. It was a great service appointment and the techs at the Houston Westchase service center paid attention to my concerns and promised to follow up with a call from the lead virtual tech team technician. I detailed this service visit in the following post:

Reduced Range - Tesla Issued a Service Bulletin for possible fix

While that service visit was great, the real meat of addressing the problem came when I spoke to the virtual tech team lead. He told me some great things about the Model 3 battery and BMS. With the knowledge of what he told me, I formulated a plan to address it myself.

So here is the deal on the Model 3 battery and why many of us might be seeing this capacity degradation.

The BMS system is not only responsible for charging and monitoring of the battery, but computing the estimated range. The way it does this is to correlate the battery's terminal voltage (and the terminal voltage of each group of parallel cells) to the capacity. The BMS tries to constantly refine and calibrate that relationship between terminal voltage and capacity to display the remaining miles.

For the BMS to execute a calibration computation, it needs data. The primary data it needs to to this is what is called the Open Circuit Voltage (OCV) of the battery and each parallel group of cells. The BMS takes these OCV readings whenever it can, and when it has enough of them, it runs a calibration computation. This lets the BMS now estimate capacity vs the battery voltage. If the BMS goes for a long time without running calibration computations, then the BMS's estimate of the battery's capacity can drift away from the battery's actual capacity. The BMS is conservative in its estimates so that people will not run out of battery before the indicator reads 0 miles, so the drift is almost always in the direction of estimated capacity < actual capacity.

So, when does the BMS take OCV readings? To take a set of OCV readings, the main HV contactor must be open, and the voltages inside the pack for every group of parallel cells must stabilize. How long does that take? Well, interestingly enough, the Model 3 takes a lot longer for the voltages to stabilize than the Model S or X. The reason is because of the battery construction. All Tesla batteries have a resistor in parallel with every parallel group of cells. The purpose of these resistors is for pack balancing. When charging to 100%, these resistors allow the low cells in the parallel group to charge more than the high cells in the group, bringing all the cells closer together in terms of their state of charge. However, the drawback to these resistors is that they are the primary cause of vampire drain.

Because Tesla wanted the Model 3 battery to be the most efficient it could be, Tesla decided to decrease the vampire drain as much as possible. One step they took to accomplish this was to increase the value of all of these resistors so that the vampire drain is minimized. The resistors in the Model 3 packs are apparently around 10x the value of the ones in the Model S/X packs. So what does this do to the BMS? Well, it makes the BMS wait a lot longer to take OCV readings, because the voltages take 10x longer to stabilize. Apparently, the voltages can stabilize enough to take OCV readings in the S/X packs within 15-20 minutes, but the Model 3 can take 3+ hours.

This means that the S/X BMS can run the calibration computations a lot easier and lot more often than the Model 3. 15-20 minutes with the contactor open is enough to get a set of OCV readings. This can happen while you're out shopping or at work, allowing the BMS to get OCV readings while the battery is at various states of charge, both high and low. This is great data for the BMS, and lets it run a good calibration fairly often.

On the Model 3, this doesn't happen. With frequent small trips, no OCV readings ever get taken because the voltage doesn't stabilize before you drive the car again. Also, many of us continuously run Sentry mode whenever we're not at home, and Sentry mode keeps the contactor engaged, thus no OCV readings can be taken no matter how long you wait. For many Model 3's, the only time OCV readings get taken is at home after a battery charge is completed, as that is the only time the car gets to open the contactor and sleep. Finally, 3 hours later, OCV readings get taken.

But that means that the OCV readings are ALWAYS at your battery charge level. If you always charge to 80%, then the only data the BMS is repeatedly collecting is 80% OCV readings. This isn't enough data to make the calibration computation accurate. So even though the readings are getting taken, and the calibration computation is being periodically run, the accuracy of the BMS never improves, and the estimated capacity vs. actual capacity continues to drift apart.

So, knowing all of this, here's what I did:

1. I made it a habit to make sure that the BMS got to take OCV readings whenever possible. I turned off Sentry mode at work so that OCV readings could be taken there. I made sure that TeslaFi was set to allow the car to sleep, because if it isn't asleep, OCV readings can't get taken.

2. I quit charging every day. Round-trip to work and back for me is about 20% of the battery's capacity, and I used to normally charge to 90%. I changed my standard charge to 80%, and then I began charging the car at night only every 3 days. So day 1 gets OCV readings at 80% (after the charge is complete), day 2 at about 60% (after 1 work trip), and day 3 at about 40% (2 work trips). I arrive back home from work with about 20% charge on that last day, and if the next day isn't Saturday, then I charge. If the next day is Saturday (I normally don't go anywhere far on Saturday), then I delay the charge for a 4th day, allowing the BMS to get OCV readings at 20%. So now my BMS is getting data from various states of charge throughout the range of the battery.

3. I periodically (once a month or so) charge to 95%, then let the car sleep for 6 hours, getting OCV readings at 95%. Don't do this at 100%, as it's not good for the battery to sit with 100% charge.

4. If I'm going to take a long drive i.e. road trip, then I charge to 100% to balance the battery, then drive. I also try to time it so that I get back home with around 10% charge, and if I can do that, then I don't charge at that time. Instead, let the car sleep 6 hours so it gets OCV readings at 10%.

These steps allowed the BMS to get many OCV readings that span the entire state of charge of the battery. This gets it good data to run an accurate calibration computation.

So what's the results?

On 1/20/2020 at 30,700 miles, I was down to 270 miles full range, which is 40.8 miles lost (15.1 %). The first good, accurate recalibration occurred 4/16/2020 at 35,600 miles and brought the full range up to 286 miles. Then another one occurred on 8/23/2020 at 41,400 miles and brought the range up to 290 miles, now only a 20 mile loss (6.9 %).

Note that to get just two accurate calibration computations by the BMS took 7 months and 11,000 miles.

So, to summarize:

1. This issue is primarily an indication/estimation problem, not real battery capacity loss.
2. Constant Sentry mode use contributes to this problem, because the car never sleeps, so no OCV readings get taken.
3. Long voltage stabilization times in the Model 3 prevent OCV readings from getting taken frequently, contributing to BMS estimation drift.
4. Constantly charging every day means that those OCV readings that do get taken are always at the same charge level, which makes the BMS calibration inaccurate.
5. Multiple accurate calibration cycles may need to happen before the BMS accuracy improves.
6. It takes a long time (a lot of OCV readings) to cause the BMS to run a calibration computation, and therefore the procedure can take months.

I would love if someone else can perform this procedure and confirm that it works for you, especially if your Model 3 is one that has a lot of apparent degradation. It will take months, but I think we can prove that this procedure will work.

Thank you very much, will try these methods and report back on a week, I turned off Sentry mode and also use TezLab to put the Model 3 in Deep sleep.

This is where I am at today.

Fred

 

[Raechris]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

I own a Model 3 and drive it only infrequently ... especially now during the Covid-19 crimp on places to go. Now I'm sure all you young'uns out there will puzzle over how I could possibly lose some sharpness in my senior years; after all, you (and I, too, when I was a young'un) are bright, quick on your feet, sharp memory, and all the rest of the admirable characteristics of not-old humans, AND YOU'LL NEVER GIVE IN TO THE RAVAGES OF AGE, EITHER. Am I not right?

The Tesla autos have sometimes been called, with pride, "a computer on wheels." However, when I describe my M3 that way to others, it's with an inward groan. Why? It is so difficult to do anything, even simple things like open the glove box. In all the ICE cars I've ever driven, it's been easy. A/C? Sure, just reach over WITHOUT HAVING TO TAKE MY EYES OFF THE ROAD and make the adjustments by touch. No way to do that in my computer on wheels.

(btw, I fully expect there will be many crash descriptions of seniors taking their eyes off the road too long and crashing into some innocent car, guard rail at the edge of a cliff, or oncoming fully loaded semi.)

Or, say you want to flip on the windshield wipers to wash off a bug flattened right in your line of vision. If you’re like me, you’ll have to pull over to the side of the road and browse through the logical decision tree on the touch screen (that saves a lot of weight, I’m sure) before you can home in, minutes later, on the part of the algorithm that gives you several choices for windshield wiper activation.

This retired aerospace engineer, who helped design the control system of the GPS satellite decades ago, longs for the simplicity of an old ICE car! Same for my wife, who refuses to drive the M3 because it is “Too complicated.”

Elon! Here’s a demographic that you might not reach until you design a simple ecar: The really senior cohort that really doesn’t need 0 – 60 in 3 seconds. (I tried to think of a name for a senior-appropriate Tesla that could be added to the S3XY lineup, but I nodded off. Maybe after my nap.)

I don't have a M3 (MS) but can't you use the talk button to control nearly all the M3 vehicle functions (E.g. wipers, glove box). This is not intended to be snarky but helpful tip if you have not tried it. My MCU1 is not very responsive to speech but when it works it works well.

 

[jpfive]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

I own a Model 3 and drive it only infrequently ... especially now during the Covid-19 crimp on places to go. Now I'm sure all you young'uns out there will puzzle over how I could possibly lose some sharpness in my senior years; after all, you (and I, too, when I was a young'un) are bright, quick on your feet, sharp memory, and all the rest of the admirable characteristics of not-old humans, AND YOU'LL NEVER GIVE IN TO THE RAVAGES OF AGE, EITHER. Am I not right?

The Tesla autos have sometimes been called, with pride, "a computer on wheels." However, when I describe my M3 that way to others, it's with an inward groan. Why? It is so difficult to do anything, even simple things like open the glove box. In all the ICE cars I've ever driven, it's been easy. A/C? Sure, just reach over WITHOUT HAVING TO TAKE MY EYES OFF THE ROAD and make the adjustments by touch. No way to do that in my computer on wheels.

(btw, I fully expect there will be many crash descriptions of seniors taking their eyes off the road too long and crashing into some innocent car, guard rail at the edge of a cliff, or oncoming fully loaded semi.)

Or, say you want to flip on the windshield wipers to wash off a bug flattened right in your line of vision. If you’re like me, you’ll have to pull over to the side of the road and browse through the logical decision tree on the touch screen (that saves a lot of weight, I’m sure) before you can home in, minutes later, on the part of the algorithm that gives you several choices for windshield wiper activation.

This retired aerospace engineer, who helped design the control system of the GPS satellite decades ago, longs for the simplicity of an old ICE car! Same for my wife, who refuses to drive the M3 because it is “Too complicated.”

Elon! Here’s a demographic that you might not reach until you design a simple ecar: The really senior cohort that really doesn’t need 0 – 60 in 3 seconds. (I tried to think of a name for a senior-appropriate Tesla that could be added to the S3XY lineup, but I nodded off. Maybe after my nap.)

I resemble this.

 

[Rickland]

Like many others, I have been concerned with loss of 100% indicated battery range on one of my Model 3s. My P3D (build date 9/13/2018, delivery date 10/8/2018) had gotten down to 270.3 miles at 100% charge on January 20, 2020, at about 30,700 miles, which is a loss of 40.8 miles since the car was new.

I posted about going to the service center to talk with them about battery degradation, which I did on March 9, 2020. It was a great service appointment and the techs at the Houston Westchase service center paid attention to my concerns and promised to follow up with a call from the lead virtual tech team technician. I detailed this service visit in the following post:

Reduced Range - Tesla Issued a Service Bulletin for possible fix

While that service visit was great, the real meat of addressing the problem came when I spoke to the virtual tech team lead. He told me some great things about the Model 3 battery and BMS. With the knowledge of what he told me, I formulated a plan to address it myself.

So here is the deal on the Model 3 battery and why many of us might be seeing this capacity degradation.

The BMS system is not only responsible for charging and monitoring of the battery, but computing the estimated range. The way it does this is to correlate the battery's terminal voltage (and the terminal voltage of each group of parallel cells) to the capacity. The BMS tries to constantly refine and calibrate that relationship between terminal voltage and capacity to display the remaining miles.

For the BMS to execute a calibration computation, it needs data. The primary data it needs to to this is what is called the Open Circuit Voltage (OCV) of the battery and each parallel group of cells. The BMS takes these OCV readings whenever it can, and when it has enough of them, it runs a calibration computation. This lets the BMS now estimate capacity vs the battery voltage. If the BMS goes for a long time without running calibration computations, then the BMS's estimate of the battery's capacity can drift away from the battery's actual capacity. The BMS is conservative in its estimates so that people will not run out of battery before the indicator reads 0 miles, so the drift is almost always in the direction of estimated capacity < actual capacity.

So, when does the BMS take OCV readings? To take a set of OCV readings, the main HV contactor must be open, and the voltages inside the pack for every group of parallel cells must stabilize. How long does that take? Well, interestingly enough, the Model 3 takes a lot longer for the voltages to stabilize than the Model S or X. The reason is because of the battery construction. All Tesla batteries have a resistor in parallel with every parallel group of cells. The purpose of these resistors is for pack balancing. When charging to 100%, these resistors allow the low cells in the parallel group to charge more than the high cells in the group, bringing all the cells closer together in terms of their state of charge. However, the drawback to these resistors is that they are the primary cause of vampire drain.

Because Tesla wanted the Model 3 battery to be the most efficient it could be, Tesla decided to decrease the vampire drain as much as possible. One step they took to accomplish this was to increase the value of all of these resistors so that the vampire drain is minimized. The resistors in the Model 3 packs are apparently around 10x the value of the ones in the Model S/X packs. So what does this do to the BMS? Well, it makes the BMS wait a lot longer to take OCV readings, because the voltages take 10x longer to stabilize. Apparently, the voltages can stabilize enough to take OCV readings in the S/X packs within 15-20 minutes, but the Model 3 can take 3+ hours.

This means that the S/X BMS can run the calibration computations a lot easier and lot more often than the Model 3. 15-20 minutes with the contactor open is enough to get a set of OCV readings. This can happen while you're out shopping or at work, allowing the BMS to get OCV readings while the battery is at various states of charge, both high and low. This is great data for the BMS, and lets it run a good calibration fairly often.

On the Model 3, this doesn't happen. With frequent small trips, no OCV readings ever get taken because the voltage doesn't stabilize before you drive the car again. Also, many of us continuously run Sentry mode whenever we're not at home, and Sentry mode keeps the contactor engaged, thus no OCV readings can be taken no matter how long you wait. For many Model 3's, the only time OCV readings get taken is at home after a battery charge is completed, as that is the only time the car gets to open the contactor and sleep. Finally, 3 hours later, OCV readings get taken.

But that means that the OCV readings are ALWAYS at your battery charge level. If you always charge to 80%, then the only data the BMS is repeatedly collecting is 80% OCV readings. This isn't enough data to make the calibration computation accurate. So even though the readings are getting taken, and the calibration computation is being periodically run, the accuracy of the BMS never improves, and the estimated capacity vs. actual capacity continues to drift apart.

So, knowing all of this, here's what I did:

1. I made it a habit to make sure that the BMS got to take OCV readings whenever possible. I turned off Sentry mode at work so that OCV readings could be taken there. I made sure that TeslaFi was set to allow the car to sleep, because if it isn't asleep, OCV readings can't get taken.

2. I quit charging every day. Round-trip to work and back for me is about 20% of the battery's capacity, and I used to normally charge to 90%. I changed my standard charge to 80%, and then I began charging the car at night only every 3 days. So day 1 gets OCV readings at 80% (after the charge is complete), day 2 at about 60% (after 1 work trip), and day 3 at about 40% (2 work trips). I arrive back home from work with about 20% charge on that last day, and if the next day isn't Saturday, then I charge. If the next day is Saturday (I normally don't go anywhere far on Saturday), then I delay the charge for a 4th day, allowing the BMS to get OCV readings at 20%. So now my BMS is getting data from various states of charge throughout the range of the battery.

3. I periodically (once a month or so) charge to 95%, then let the car sleep for 6 hours, getting OCV readings at 95%. Don't do this at 100%, as it's not good for the battery to sit with 100% charge.

4. If I'm going to take a long drive i.e. road trip, then I charge to 100% to balance the battery, then drive. I also try to time it so that I get back home with around 10% charge, and if I can do that, then I don't charge at that time. Instead, let the car sleep 6 hours so it gets OCV readings at 10%.

These steps allowed the BMS to get many OCV readings that span the entire state of charge of the battery. This gets it good data to run an accurate calibration computation.

So what's the results?

On 1/20/2020 at 30,700 miles, I was down to 270 miles full range, which is 40.8 miles lost (15.1 %). The first good, accurate recalibration occurred 4/16/2020 at 35,600 miles and brought the full range up to 286 miles. Then another one occurred on 8/23/2020 at 41,400 miles and brought the range up to 290 miles, now only a 20 mile loss (6.9 %).

Note that to get just two accurate calibration computations by the BMS took 7 months and 11,000 miles.

So, to summarize:

1. This issue is primarily an indication/estimation problem, not real battery capacity loss.
2. Constant Sentry mode use contributes to this problem, because the car never sleeps, so no OCV readings get taken.
3. Long voltage stabilization times in the Model 3 prevent OCV readings from getting taken frequently, contributing to BMS estimation drift.
4. Constantly charging every day means that those OCV readings that do get taken are always at the same charge level, which makes the BMS calibration inaccurate.
5. Multiple accurate calibration cycles may need to happen before the BMS accuracy improves.
6. It takes a long time (a lot of OCV readings) to cause the BMS to run a calibration computation, and therefore the procedure can take months.

I would love if someone else can perform this procedure and confirm that it works for you, especially if your Model 3 is one that has a lot of apparent degradation. It will take months, but I think we can prove that this procedure will work.

isn’t battery/range also affected by temperatures? Especially reduced range in cold weather?

 

[MikeHolliday]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

I own a Model 3 and drive it only infrequently ... especially now during the Covid-19 crimp on places to go. Now I'm sure all you young'uns out there will puzzle over how I could possibly lose some sharpness in my senior years; after all, you (and I, too, when I was a young'un) are bright, quick on your feet, sharp memory, and all the rest of the admirable characteristics of not-old humans, AND YOU'LL NEVER GIVE IN TO THE RAVAGES OF AGE, EITHER. Am I not right?

The Tesla autos have sometimes been called, with pride, "a computer on wheels." However, when I describe my M3 that way to others, it's with an inward groan. Why? It is so difficult to do anything, even simple things like open the glove box. In all the ICE cars I've ever driven, it's been easy. A/C? Sure, just reach over WITHOUT HAVING TO TAKE MY EYES OFF THE ROAD and make the adjustments by touch. No way to do that in my computer on wheels.

(btw, I fully expect there will be many crash descriptions of seniors taking their eyes off the road too long and crashing into some innocent car, guard rail at the edge of a cliff, or oncoming fully loaded semi.)

Or, say you want to flip on the windshield wipers to wash off a bug flattened right in your line of vision. If you’re like me, you’ll have to pull over to the side of the road and browse through the logical decision tree on the touch screen (that saves a lot of weight, I’m sure) before you can home in, minutes later, on the part of the algorithm that gives you several choices for windshield wiper activation.

This retired aerospace engineer, who helped design the control system of the GPS satellite decades ago, longs for the simplicity of an old ICE car! Same for my wife, who refuses to drive the M3 because it is “Too complicated.”

Elon! Here’s a demographic that you might not reach until you design a simple ecar: The really senior cohort that really doesn’t need 0 – 60 in 3 seconds. (I tried to think of a name for a senior-appropriate Tesla that could be added to the S3XY lineup, but I nodded off. Maybe after my nap.)

I am a senior also and love my Model Y. If you are having a problem, use Voice Commands...

You only need to push the Right Button on the Steering Wheel and state, Turn on Air Conditioner, Turn off Air Conditioner, Increase Fan 5 or Decrease Fan 3, Set Climate Control 72 degrees, Play Beetles Music, Play Simon & Garfunkel, Play Disney Music (for grandkids), Open Frunk, Open Trunk, Set Cruise to 75, Windshield Wipers Speed 2, Windshield Wipers Auto, Windshield Wipers Off, Open Easter Eggs…

I love Voice Commands!!!

 

[Dave EV]

Like many others, I have been concerned with loss of 100% indicated battery range on one of my Model 3s. My P3D (build date 9/13/2018, delivery date 10/8/2018) had gotten down to 270.3 miles at 100% charge on January 20, 2020, at about 30,700 miles, which is a loss of 40.8 miles since the car was new.

I posted about going to the service center to talk with them about battery degradation, which I did on March 9, 2020. It was a great service appointment and the techs at the Houston Westchase service center paid attention to my concerns and promised to follow up with a call from the lead virtual tech team technician. I detailed this service visit in the following post:

Reduced Range - Tesla Issued a Service Bulletin for possible fix

While that service visit was great, the real meat of addressing the problem came when I spoke to the virtual tech team lead. He told me some great things about the Model 3 battery and BMS. With the knowledge of what he told me, I formulated a plan to address it myself.

So here is the deal on the Model 3 battery and why many of us might be seeing this capacity degradation.

The BMS system is not only responsible for charging and monitoring of the battery, but computing the estimated range. The way it does this is to correlate the battery's terminal voltage (and the terminal voltage of each group of parallel cells) to the capacity. The BMS tries to constantly refine and calibrate that relationship between terminal voltage and capacity to display the remaining miles.

For the BMS to execute a calibration computation, it needs data. The primary data it needs to to this is what is called the Open Circuit Voltage (OCV) of the battery and each parallel group of cells. The BMS takes these OCV readings whenever it can, and when it has enough of them, it runs a calibration computation. This lets the BMS now estimate capacity vs the battery voltage. If the BMS goes for a long time without running calibration computations, then the BMS's estimate of the battery's capacity can drift away from the battery's actual capacity. The BMS is conservative in its estimates so that people will not run out of battery before the indicator reads 0 miles, so the drift is almost always in the direction of estimated capacity < actual capacity.

So, when does the BMS take OCV readings? To take a set of OCV readings, the main HV contactor must be open, and the voltages inside the pack for every group of parallel cells must stabilize. How long does that take? Well, interestingly enough, the Model 3 takes a lot longer for the voltages to stabilize than the Model S or X. The reason is because of the battery construction. All Tesla batteries have a resistor in parallel with every parallel group of cells. The purpose of these resistors is for pack balancing. When charging to 100%, these resistors allow the low cells in the parallel group to charge more than the high cells in the group, bringing all the cells closer together in terms of their state of charge. However, the drawback to these resistors is that they are the primary cause of vampire drain.

Because Tesla wanted the Model 3 battery to be the most efficient it could be, Tesla decided to decrease the vampire drain as much as possible. One step they took to accomplish this was to increase the value of all of these resistors so that the vampire drain is minimized. The resistors in the Model 3 packs are apparently around 10x the value of the ones in the Model S/X packs. So what does this do to the BMS? Well, it makes the BMS wait a lot longer to take OCV readings, because the voltages take 10x longer to stabilize. Apparently, the voltages can stabilize enough to take OCV readings in the S/X packs within 15-20 minutes, but the Model 3 can take 3+ hours.

This means that the S/X BMS can run the calibration computations a lot easier and lot more often than the Model 3. 15-20 minutes with the contactor open is enough to get a set of OCV readings. This can happen while you're out shopping or at work, allowing the BMS to get OCV readings while the battery is at various states of charge, both high and low. This is great data for the BMS, and lets it run a good calibration fairly often.

On the Model 3, this doesn't happen. With frequent small trips, no OCV readings ever get taken because the voltage doesn't stabilize before you drive the car again. Also, many of us continuously run Sentry mode whenever we're not at home, and Sentry mode keeps the contactor engaged, thus no OCV readings can be taken no matter how long you wait. For many Model 3's, the only time OCV readings get taken is at home after a battery charge is completed, as that is the only time the car gets to open the contactor and sleep. Finally, 3 hours later, OCV readings get taken.

But that means that the OCV readings are ALWAYS at your battery charge level. If you always charge to 80%, then the only data the BMS is repeatedly collecting is 80% OCV readings. This isn't enough data to make the calibration computation accurate. So even though the readings are getting taken, and the calibration computation is being periodically run, the accuracy of the BMS never improves, and the estimated capacity vs. actual capacity continues to drift apart.

So, knowing all of this, here's what I did:

1. I made it a habit to make sure that the BMS got to take OCV readings whenever possible. I turned off Sentry mode at work so that OCV readings could be taken there. I made sure that TeslaFi was set to allow the car to sleep, because if it isn't asleep, OCV readings can't get taken.

2. I quit charging every day. Round-trip to work and back for me is about 20% of the battery's capacity, and I used to normally charge to 90%. I changed my standard charge to 80%, and then I began charging the car at night only every 3 days. So day 1 gets OCV readings at 80% (after the charge is complete), day 2 at about 60% (after 1 work trip), and day 3 at about 40% (2 work trips). I arrive back home from work with about 20% charge on that last day, and if the next day isn't Saturday, then I charge. If the next day is Saturday (I normally don't go anywhere far on Saturday), then I delay the charge for a 4th day, allowing the BMS to get OCV readings at 20%. So now my BMS is getting data from various states of charge throughout the range of the battery.

3. I periodically (once a month or so) charge to 95%, then let the car sleep for 6 hours, getting OCV readings at 95%. Don't do this at 100%, as it's not good for the battery to sit with 100% charge.

4. If I'm going to take a long drive i.e. road trip, then I charge to 100% to balance the battery, then drive. I also try to time it so that I get back home with around 10% charge, and if I can do that, then I don't charge at that time. Instead, let the car sleep 6 hours so it gets OCV readings at 10%.

These steps allowed the BMS to get many OCV readings that span the entire state of charge of the battery. This gets it good data to run an accurate calibration computation.

So what's the results?

On 1/20/2020 at 30,700 miles, I was down to 270 miles full range, which is 40.8 miles lost (15.1 %). The first good, accurate recalibration occurred 4/16/2020 at 35,600 miles and brought the full range up to 286 miles. Then another one occurred on 8/23/2020 at 41,400 miles and brought the range up to 290 miles, now only a 20 mile loss (6.9 %).

Note that to get just two accurate calibration computations by the BMS took 7 months and 11,000 miles.

So, to summarize:

1. This issue is primarily an indication/estimation problem, not real battery capacity loss.
2. Constant Sentry mode use contributes to this problem, because the car never sleeps, so no OCV readings get taken.
3. Long voltage stabilization times in the Model 3 prevent OCV readings from getting taken frequently, contributing to BMS estimation drift.
4. Constantly charging every day means that those OCV readings that do get taken are always at the same charge level, which makes the BMS calibration inaccurate.
5. Multiple accurate calibration cycles may need to happen before the BMS accuracy improves.
6. It takes a long time (a lot of OCV readings) to cause the BMS to run a calibration computation, and therefore the procedure can take months.

I would love if someone else can perform this procedure and confirm that it works for you, especially if your Model 3 is one that has a lot of apparent degradation. It will take months, but I think we can prove that this procedure will work.

Informative post, which I basically summarize as:

Charge to whatever SOC you feel is best, then recharge once you get below 100 miles or so.

Another observation which many people have been saying for a long time - change the display to show % instead of miles and stop worrying about it! No actual range has been lost.

That said, the comments about the balancing resistors being made 10x smaller to reduce vampire drain and thus balancing taking longer, don't make any sense to me. The amount of energy required to balance the pack is the same whether you use large resistors or small resistors is the same, so the load put on each module by the balancing circuit should have no effect on vampire drain in the BMS. Also, if Tesla wanted to reduce this error, they could easily change the BMS to pause balancing for a long enough to get accurate OCV voltages before proceeding with balancing, eliminating the need for the car to sit for 3 hours before taking OCV data.

 

[Webeevdrivers]

Have you tried voice commands? There are quite a few now.
Tap and let go; then speak after a moment or two. (old way was tap and hold).
See this list:
V10.2 Tesla Voice Commands

wow. Invaluable. Thanks.

 

[11dString]

Thank you for such a detailed explanation. Great post!

 

[LDMD7]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

Not at all. OP is merely explaining that actual range > predicted range if the car doesn’t get a chance to sleep and perform this process. Your M3 will be just as awesome to drive whether you do as OP did.

As for reaching for the A/C, it’s muscle memory. I’m 61 and are ICE controls easier? Sure! But your brain builds new pathways when you do things that are difficult. Which helps you maintain your faculties and protects you from memory loss and that slippery slope.

So a Tesla can help you stay young!

 

[Jromf]

I know this is written in English but, dag nab it, I can barely understand it. Even with a law school education. Will study it, though.

 

[FarmerDave]

I also think that there are too many simple functions which require using the touch screen and that doing so while driving is dangerous. With my previous car I could adjust the temperature and fan speed without taking my eyes off of the road. Same with operating the wipers. Then too there is the problem having the type size too small to read while wearing distance glasses. I really to like the car, but the controls are likely to cause a crash.

As mentioned previously, you can operate the wipers for a quick sweep by pressing the button on the end of the stalk, or hold it in for the washer. Temperature & fan speed can be changed using voice commands after pressing the right hand button on the steering wheel.

As with most devices, for best results RTFM.

 

[CSFTN]

I am impressed with the technical acumen detailed here. It saddens me, though, because it is just one more piece of evidence to me that Tesla autos are not for the senior set (of which I am a reluctant member).

Respectfully disagree. You could jus drive it and don't worry about the miles of range. Just do that which the Nav tells you, and you will be fine. Unless of course you are traversing a gap of 300+ miles with somewhere between 0 and 2 DCFC on the route.

 

[SoloPilot]

We could build an app that charges the vehicle to specific levels each evening. That would help generate many calibration points.

 

[ElectricMozart]

My LR AWD range has been steadily declining over the past 2 years and I'm nearly at the level the OP has at 272 miles at 100% SOC. I've tried lots of "calibrations" with no luck. However, this information is promising so I'll try this too with some hope. My commute is 130 miles roundtrip so I usually charge daily but I will try to rest the battery at different SOC's and see if it helps. Thank you for this info. Here's hoping.

Edit, forgot to mention, I just had my battery breather valves replaces this week due to unusual loud pops when supercharging. Coincidentally, I lost another 8 miles of range shortly after. Unsure if it had anything to do with it.

 

[ElectricMozart]

Another observation which many people have been saying for a long time - change the display to show % instead of miles and stop worrying about it! No actual range has been lost.

However the car thinks the range has been lost. I'm unlikely to drive my car to 0 to find out if its hiding range so I drive within the 20-90% of the battery displayed range. I recently went on a 800 mile drive with a 250 mile stretch with no tesla charging. My displayed range is 272 miles and my car's nav plotted the route as if I could make it with 10% left at my destination. Well, I could not..even driving at the rated wh/mi, I was gonna be stuck so luckily I had the foresight to buy the expensive Chademo adapter and plug in at a 3rd party charger on the way to add another 20% or so. Point is, on long drives, its good to know what the cars estimated range in miles is because outside major interstates, tesla charging can be vastly spread out and the nav estimations are far to optimistic.

 

[earthwormjim]

Another observation which many people have been saying for a long time - change the display to show % instead of miles and stop worrying about it! No actual range has been lost.

I hate when this suggestion is posted. It display true ignorance on the part of the poster, and belittles people legitimately concerned with the batteries in their car. The range display is our only readily available window into the supposed health of the batteries.

Besides, percentage will still reveal the issue you are trying to bury your head into the sand to not see. You'll see that your ending percentage after your daily commute will be lower and lower, despite maintaining the same wh/mi and charging habits. My commute, which used to take my car from 90% to 76-75%, now takes my car from 90% to 68-67%, despite maintaining roughly same wh/mi average.

 

[gaswalla]

there are lots of really smart people here.. so impressed
and a bunch of people who keep posting about how to open the glovebox with voice command