Decreasing rated range.

[glhs272]

I wonder, would operating a battery pack out of balance for long periods cause permanent range degradation over the long term compared to a pack kept in balance all other things being equal? The thinking being that because some cells are operating consistently at higher voltage than other cells, they will wear unevenly. Either the higher voltage cells degrade faster because of the higher voltage or the lower voltage cells degrade faster due to higher current draw and thus being stressed more I don't know. And because the battery pack will only charge until the highest voltage cells reach their target voltage, the rest of the pack may be able to take more charge but can't because a few of them have "aged" faster than the others. Sort of the weakest link situation. Therefore a battery pack that is consistently balanced over it's lifetime will wear the cells more evenly, thus allowing more of the cells to reach full charge. Anyway, this is poorly explained but I think some of you might catch what I am saying, so what are your thoughts, bogus or a potential issue?

- - - Updated - - -

Question about 90% "balancing" method: I've never witnessed the trickle charge "solid green ring of light" at the charge port that you get when doing a 100% range charge. Does this happen during a 90% charge?

No, I don't see the trickle charge happen during a 90% charge. However, that doesn't mean it's not balancing. My understanding is balancing is occurring inside the battery at the BMB level, by bleeding off voltage to the cell groups that are higher than the rest. It doesn't need to be charging to balance. It just need to be at a high enough state of charge in order to accurately balance, thus if the state of charge is below 90% the software says "don't bother balancing".

Also, I will note that this is my "conjecture" based off what I have personally experienced and what I have seen inside the battery. This is not a fact and I don't want people to think that I have some special inside knowledge of Tesla's engineering. Although I will admit that I am an engineer professionally and mostly work in electro hydraulic control systems engineering and software.

 

[FredTMC]

Glhs... Thanks for your explanation. I figured it was part of this "shunting" that has been discussed...

 

[hans]

I wonder, would operating a battery pack out of balance for long periods cause permanent range degradation over the long term compared to a pack kept in balance all other things being equal? The thinking being that because some cells are operating consistently at higher voltage than other cells, they will wear unevenly.

It shouldn't. That's why we see lower range because the higher cells are not allowed to go any higher than the normal maximum allowed voltage. If these cells were allowed to go to a higher voltage that would cause more permanent damage. That's my understanding at least.

 

[Vger]

Yes, this has been observed and reported in this thread. Turning on range mode seems to add 2-4 miles rated range.

Ahh, I guess that partially explains my recent 270 mi range charges; I have been running in range/Eco mode this whole trip, since the weather is moderate (both ways). Next time I do one on the way home, I will turn off range mode after the charge and see what is displayed.

 

[qwk]

Question about 90% "balancing" method: I've never witnessed the trickle charge "solid green ring of light" at the charge port that you get when doing a 100% range charge. Does this happen during a 90% charge?

Yes

 

[mknox]

Ahh, I guess that partially explains my recent 270 mi range charges;

Are you speaking of 270 Ideal or Rated miles? I always use (and speak of) Rated Miles and that might be part of my confusion. I believe your car has an A-pack battery like mine. I never saw anything above 265 Rated Miles when the car was new, but that would translate, I believe, to 300 Ideal Miles.

 

[Vger]

Are you speaking of 270 Ideal or Rated miles? I always use (and speak of) Rated Miles and that might be part of my confusion. I believe your car has an A-pack battery like mine. I never saw anything above 265 Rated Miles when the car was new, but that would translate, I believe, to 300 Ideal Miles.

Rated miles. I did see 270 a few times when new, but again, that would have been with the Range/Eco setting in force. Without that, my original rated miles on a range charge would have been closer to 265. On Tuesday AM, I will do a range charge as I leave here and head to Chicago before head back west on I-90. I plan to check what the reading is in both Range/Eco and non-Range/Eco mode.

I think that the re-calibration that Tesla did with 5.9(?), combined with recent deep cycling on the road trip, combined with Range/Eco mode all together resulted in these recent eye-popping 100% charge numbers.

- - - Updated - - -

BTW, I always operate the car in the units of the country I am in, so while it is alway kms in Canada, since I am in the US for this trip, that is why I am reporting miles.

 

[tezco]

I wonder if the eco setting algorithm also adjusts the calculated rated range figure slightly, depending on the outside temperature? Does the ideal figure also vary at the same SOC, if eco is selected or deselected?

 

[RomainiacWV]

So as expected, the response I recieved was a bit generic regarding the battery from recent SC visit. Engineering said they looked at the battery and that the capacity was "normal". They did not give me a total capacity read.

I guess the most confusing thing is that they said I should return to "daily" charging as recommended in the owner's manual at 90%. They said to stop 60% charge and felt that the range would come back "in time". I have issue with this as I dont feel the manual explicitly tells you to charge at 90% does it?? I'll have to look later. I know the center console says to charge to "daily needs". When I addressed this with Sc they simply agreed, and said that they dont know why there is a descrepency.

In tongue and cheek, I was told to "follow Tesla engineers" advice and not "forum" advice. I am a medical provider and I do understand the frustration with patients self diagnosing online. However, I feel there is often alot more good advice on here than not.

The fact they want me to charge at 90% lends creedance to the "imbalance" theory but they would not commit to it and say that software still involved.

Going to be roadtripping the car and cycling the battery later this month several times. Going to give it through that period. If range loss continues or shows no significant improvement, plan to write a letter to Tesla, just asking they answer some basic questions on how to best care for this car. I will post again here and on Tesla forum if it comes to it. A bit frustrated but know that they will make it right in the end. Hoping I see some miraculous range recovery like others have with deep cycle.

Looking forward to next week, X res holder so hoping that is revealed but know that the III would make a huge splash

 

[tezco]

...I guess the most confusing thing is that they said I should return to "daily" charging as recommended in the owner's manual at 90%. They said to stop 60% charge and felt that the range would come back "in time"...

My manual says to set the charge limit anywhere between 50 and 90% for maximum battery longevity, so I'd trust the manual over the SC banter. I don't think that you damaged the battery by leaving it at 60%. I'm certainly not going to follow the advice of some forum members who advocate setting routine charging @ 100%.

 

[slyastro]

I just passed the 60 000 Miles mark (96 954 KM) with my Model S. With range mode ON, I get 362 KM (225 Miles) at 90% and 403 KM (250 Miles) at 100%.

My battery pack is the «A» version.

 

[AmpedRealtor]

I'm one of those people who has been charging as little as possible and have generally kept my car in the 50%-70% range. I've only max charged (100%) twice. The last time I max charged, it only went to 289 ideal miles. Since then, I've been keeping the car at 90% per the service center's advice after they checked my battery. After two weeks at 90%, I am now up to 296 ideal miles at 100% and rising. Even if it doesn't go above 296 ideal miles, that still reflects only a 1.3% degradation after 1 year and 13,000 miles. Not bad!

Use ideal miles to check your battery capacity, not rated miles. I have a B pack.

 

[jyc]

We've generally been charging on the low side for our vehicle, which now has 27,500 miles on a B pack.

Was down to 218 rated miles for a 90% charge, and then decided for the last 4 weeks, to charging up to 90% overnight. Slightly less charging during the day at work, and ran the pack down to 23 rated miles a few days ago and supercharged to 160 to get home. Since then 90% has increased 6 rated miles to 224 and still seems to be rising.

Seems reassuring that the battery isn't really all that degraded (even though I'm not using ideal miles as suggested by AmpedRealtor).

 

[brianman]

Use ideal miles to check your battery capacity, not rated miles. I have a B pack.

Ew. No thanks. If I'm going to go with fantasy coefficients, I want to use one that's at least closer to my actual usage.

That said, +1 to the request to have an option to replace every mi,km and mph/kph unit related to energy or power in the UI with kW or kWh, respectively.

 

[tomas]

Ew. No thanks. If I'm going to go with fantasy coefficients, I want to use one that's at least closer to my actual usage.

That said, +1 to the request to have an option to replace every mi,km and mph/kph unit related to energy or power in the UI with kW or kWh, respectively.

Honest officer, I really did not know I was going 90! My car only reports kW!

 

[brianman]

Honest officer, I really did not know I was going 90! My car only reports kW!

Hence the qualifier. The speedometer isn't "related to energy or power" (at least not directly).

 

[AmpedRealtor]

Ew. No thanks. If I'm going to go with fantasy coefficients, I want to use one that's at least closer to my actual usage.

That said, +1 to the request to have an option to replace every mi,km and mph/kph unit related to energy or power in the UI with kW or kWh, respectively.

Looking at ideal miles is a better way of determining what's really in your battery. Why? Because ideal range calculation has not been changed, but Tesla keeps tweaking the rated range algorithm as has been shown with the numbers changing after specific software updates. Tesla has also stated that the rated range algorithm has been changed a number of times to better estimate range in real world driving conditions. As such, it's not a good indicator of whether you have any battery degradation. It's a moving target.

Ideal mile calculation hasn't changed. Based on my latest numbers, I'm seeing 254 rated miles and 296 ideal miles. Based on ideal miles, if they don't rise over time, I've lost 1.3% capacity. Based on rated range, I've lost 4.2% capacity, or over 3x as much. It's not a good metric for determining battery loss, if any.

 

[nwdiver]

I've got a 'B' pack with ~55k miles on it... I've been getting ~245 miles rated range @ 100% SOC. I usually charge to ~160 miles for daily travel. I have noticed that when I charge to 100% SOC my range will sometimes stay at 246 for ~10 miles even though my 'since last charge' meter indicates I've used ~3kWh.

 

[AmpedRealtor]

I've got a 'B' pack with ~55k miles on it... I've been getting ~245 miles rated range @ 100% SOC. I usually charge to ~160 miles for daily travel. I have noticed that when I charge to 100% SOC my range will sometimes stay at 246 for ~10 miles even though my 'since last charge' meter indicates I've used ~3kWh.

What is your ideal range number at 100%?

 

[brianman]

Looking at ideal miles is a better way of determining what's really in your battery.

So you have confidence that the rated calculation has changed but that ideal never will? Interesting.

- - - Updated - - -

Looking at ideal miles is a better way of determining what's really in your battery.

We'll just have to (hopefully) agree to disagree here.

When I get, say, 200 miles of range per charge and metric A says I should be getting 221 and metric B says I should be getting > 250 then I like metric A better.

"What's really in your battery" is not of interest for this purpose.

And for the record, once again, Projected got it better than either Rated, Ideal, Typical, or anything else Tesla has done with my firmware since. I wish I could get Projected back on my instrument cluster, but Tesla owns all the cards here. I'm powerless in this regard.