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Battery degradation or BMS error?

Hi everyone, I slow-charge (220v) my model 3 to 90% (confirmed by the battery% display). Initially, it used to estimate a 90% range of 232 miles, but it has steadily been dropping. Yesterday I saw an estimate of 225 miles when I unplugged. I only have 4k miles on it, and I average about 210-220wh/mile so I doubt the lower estimate is down to driving habits. I also haven't seen an upward recalibration with supercharging.

On the one hand, I'm not that worried since it's only a 7 miles drop, but I don't know if that type of monotonic decrease is everyone's experience, and within BMS margin of error.

Thoughts? Thanks!
 
Hi everyone, I slow-charge (220v) my model 3 to 90% (confirmed by the battery% display). Initially, it used to estimate a 90% range of 232 miles, but it has steadily been dropping. Yesterday I saw an estimate of 225 miles when I unplugged. I only have 4k miles on it, and I average about 210-220wh/mile so I doubt the lower estimate is down to driving habits. I also haven't seen an upward recalibration with supercharging.

On the one hand, I'm not that worried since it's only a 7 miles drop, but I don't know if that type of monotonic decrease is everyone's experience, and within BMS margin of error.

Thoughts? Thanks!

Well within the margin of error. I don’t think supercharging will have any effect on calibration.
 

ewoodrick

Well-Known Member
Apr 13, 2018
5,289
4,293
Buford, GA
You didn't really indicate how long that you have had the car. But at 4000 miles, I'm going to guess maybe 4 months.
Every few months, let it charge to 100%, and that's preferably as you take a longer trip, because you need take a longer trip for personal sanity sake.

7 mile is nothing to think about. Software updates could have caused that differential.
 
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sperkin

Active Member
Mar 23, 2017
1,010
1,185
Los Angeles, CA
The range indicated is not accurate. I think it’s based on how you drove. Most will not agree, and I can’t prove it. I only have some personal experiences and examples.

Below graph, you can see I drove 231 miles on 7/15, and 175 miles on 7/19, but in fact I only drove 90 miles on both days. I lost a lot of range, but vampire drain is so low that it didn’t even show. You can see 7/11 and 7/17 also. It’s weekdays and I just commute to work and back. Never went over 90 miles, but shows I drove more than 150+ miles.

There are times I get to work with 140miles of range in the day, but return at night with 155miles of range.

Also, those days that it registered I drove a lot of miles was when I drove my car hard the last 5 minutes before shutting down the car. I would get home with 210mile range at night but in the morning only about 170 miles of range. Then I would drive 45 miles to work and it would show 140 miles left, but later shows 155 after work. The battery indicate that I only used 15miles of battery to go 45 miles.

So just take range indicator as an average range. Not actual so any little changes you see is probably normal. In an other thread about Supercharging you can see my battery is degrading, but I’m sitting at a supercharger now and it looks like I’m going to get 310 at full charge. Will update my other thread once i’m Full.

5E60F9B4-7FF3-475E-9ECA-3948B0B1DD31.jpeg
82B293C8-2D00-4E59-9FAE-2421B162B03F.jpeg
 
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darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,178
Canada
You didn't really indicate how long that you have had the car. But at 4000 miles, I'm going to guess maybe 4 months.
Every few months, let it charge to 100%, and that's preferably as you take a longer trip, because you need take a longer trip for personal sanity sake.

OP, don't do this. Don't charge to 100% unless you are headed on a trip and 90% won't get you reasonably safely to your next supercharger stop. There's no point to charge to 100% and damage the battery. My car recalibrated down and up several times over the course of a few months and I never charge to 100% to acheive this. I'm back to where I started 5000 mi after getting the car, 90% is the same as 90% on day one. In the intervening time I saw as much as 5 miles lower, if not 6, at 90%.
 
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darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,178
Canada
The range indicated is not accurate. I think it’s based on how you drove. Most will not agree, and I can’t prove it. I only have some personal experiences and examples.

The Model 3 battery gauge is NOT a guess-o-meter that guesses your range based on past driving. That's the "projected" number in the Energy App. You can see this in the Tesla programming API where "battery_range" matches the display, and "est_battery_range" matches the last 30 miles (or last 50 km) energy app projected #.

Miles on the dashboard next to the battery icon are a direct mapping of underlying estimated kWh in the pack multiplied by a fixed constant for your specific model/trim of car. You can think of "miles" there as "units of energy".
 
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I have a Model 3 LR RWD (325 mile range) that I bought in March 2019. Up until say three weeks ago, charging to 80% showed the range as 260-262 and charging it to 90% showed the range as 291-293 (80% of 325 = 260 and 90% of 325 = 292.5).

Now, over the past 2 weeks or so, charging to 80% has dropped from 260ish to 257 to 255. Similarly, 90% dropped from 290ish to 287 to 285. I contacted the service center and they asked me to bring the battery down to 10-15% and then charge it to 90% and leave it unplugged for a while so it can re-calibrate. I did that and charging to 90% just showed the range as 282 after completion...:/

My driving/charging habits have not changed. The only thing I can think of is that my car was not receiving updates a few weeks ago, so I took it in just before I started noticing the drop and they had pushed 2019.28.3.1 on it. I have noticed the range drop ever since. The numbers seem to be more in sync with the 310 range AWD. Is this something to worry about? Is it possible that the muppet that pushed the update to my car probably thought it was a 310 range AWD and screwed something up? Btw, I only have about 8200 miles on it.
 
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darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,178
Canada
@darth_vad3r Informative posts - what are your charging habits?

I have an SR+ and use ~20% daily for commuting. I used to charge to 90% daily at work for a couple months until I saw the light and realized I didn't need to leave my battery so high all the time. Now I aim for 70-50% cycle and creep up to 90's pre-weekend or pre-trip.
 

VT_EE

Active Member
Apr 22, 2017
2,533
3,560
Earth
I have a Model 3 LR RWD (325 mile range) that I bought in March 2019. Up until say three weeks ago, charging to 80% showed the range as 260-262 and charging it to 90% showed the range as 291-293 (80% of 325 = 260 and 90% of 325 = 292.5).

Now, over the past 2 weeks or so, charging to 80% has dropped from 260ish to 257 to 255. Similarly, 90% dropped from 290ish to 287 to 285. I contacted the service center and they asked me to bring the battery down to 10-15% and then charge it to 90% and leave it unplugged for a while so it can re-calibrate. I did that and charging to 90% just showed the range as 282 after completion...:/

My driving/charging habits have not changed. The only thing I can think of is that my car was not receiving updates a few weeks ago, so I took it in just before I started noticing the drop and they had pushed 2019.28.3.1 on it. I have noticed the range drop ever since. The numbers seem to be more in sync with the 310 range AWD. Is this something to worry about? Is it possible that the muppet that pushed the update to my car probably thought it was a 310 range AWD and screwed something up? Btw, I only have about 8200 miles on it.
They changed something. Mine has done the exact same thing.
 
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OP, don't do this. Don't charge to 100% unless you are headed on a trip and 90% won't get you reasonably safely to your next supercharger stop. There's no point to charge to 100% and damage the battery. My car recalibrated down and up several times over the course of a few months and I never charge to 100% to acheive this. I'm back to where I started 5000 mi after getting the car, 90% is the same as 90% on day one. In the intervening time I saw as much as 5 miles lower, if not 6, at 90%.
I totally agree with DarthVader. Do not charge to 100% for any reason other than you want to drive far. You don't need to calibrate anything like SoC or worry about balancing. The advice to charge to 100% is unscientific and not ideal for your battery.
 
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They changed something. Mine has done the exact same thing.

Any luck with yours? I am at 280-282 at 90%, 251-252 at 80%. and 312 at 100%

I spoke with another tech from the same SC who at first said that the EPA was 310. I had to correct him and point out the difference between AWD and RWD to which he responded saying that it was expected degradation. I am not sure if he was actually providing me an educated response or was just blowing me off.

I have set up an appointment with a different SC. they have not "released" my appointment yet, so we will see.
 

VT_EE

Active Member
Apr 22, 2017
2,533
3,560
Earth
Any luck with yours? I am at 280-282 at 90%, 251-252 at 80%. and 312 at 100%

I spoke with another tech from the same SC who at first said that the EPA was 310. I had to correct him and point out the difference between AWD and RWD to which he responded saying that it was expected degradation. I am not sure if he was actually providing me an educated response or was just blowing me off.

I have set up an appointment with a different SC. they have not "released" my appointment yet, so we will see.
My 100% has been floating between 306 and 316. All this variation is due to software and not the battery failing. I’ve now set the range estimate to % and don’t pay attention anymore. I continue to use the energy app which is much better at estimating range on trips.
 

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