Decreasing rated range.

[SteveS0353]

My 2014 85kWh Model S is a ~3 months old, and I've driven ~4,700 miles. When the pack was new, a range charge was 267 miles (expected, software version 5.12). I picked the vehicle up at the Fremont factory with a range charge and drove to San Diego, and then up and down California a couple of times. I've range charged a handful of times, and mostly charged with my HPWC at 56A to 70% SoC each night.

There has been a few software updates since new, and it's now on 6.0 (1.67.43), the last update in the last week or so. Sometime in the last week or so, I noticed that the 70% SoC range has dropped from 187 to 180. I've driven the car down to the yellow (<50 miles remaining) a few times in the last couple of weeks, then recharged to 70% SoC each night.

Today, I range charged (first time in a long while), and it reached 255 miles before signaling completion. That's a 4.5% reduction in max rated range, roughly consistent with the 70% SoC range reduction from 187 to 180.

I didn't expect that rate of degradation in ~3 months and 4,700 miles. Before I tackle the San Diego SC about this, I thought I'd ask the good folks on this forum if this is "normal". Could this be a software update artifact? Does my battery need rebalancing -- and how do I do that? Do I have cause for concern?

 

[tomas]

Try charging at 90% for 10 days. That will balance. If you don't get 5 mi back I'd be surprised. Regardless, your experience not odd, most batteries drop 5% year 1 then little thereafter.

 

[gaswalla]

My 2014 85kWh Model S is a ~3 months old, and I've driven ~4,700 miles. When the pack was new, a range charge was 267 miles (expected, software version 5.12). I picked the vehicle up at the Fremont factory with a range charge and drove to San Diego, and then up and down California a couple of times. I've range charged a handful of times, and mostly charged with my HPWC at 56A to 70% SoC each night.

There has been a few software updates since new, and it's now on 6.0 (1.67.43), the last update in the last week or so. Sometime in the last week or so, I noticed that the 70% SoC range has dropped from 187 to 180. I've driven the car down to the yellow (<50 miles remaining) a few times in the last couple of weeks, then recharged to 70% SoC each night.

Today, I range charged (first time in a long while), and it reached 255 miles before signaling completion. That's a 4.5% reduction in max rated range, roughly consistent with the 70% SoC range reduction from 187 to 180.

I didn't expect that rate of degradation in ~3 months and 4,700 miles. Before I tackle the San Diego SC about this, I thought I'd ask the good folks on this forum if this is "normal". Could this be a software update artifact? Does my battery need rebalancing -- and how do I do that? Do I have cause for concern?

your 'problem' is due to charging to 70%.... please try charging to 90% as suggested... try it every day for 3 weeks, and then range charge it twice in a row .. you will be over 260 miles guaranteed.

 

[SteveS0353]

Try charging at 90% for 10 days. That will balance. If you don't get 5 mi back I'd be surprised. Regardless, your experience not odd, most batteries drop 5% year 1 then little thereafter.

your 'problem' is due to charging to 70%.... please try charging to 90% as suggested... try it every day for 3 weeks, and then range charge it twice in a row .. you will be over 260 miles guaranteed.

Thanks Guys. I will do the 90% SoC charge starting tonight.

 

[Cottonwood]

Thanks Guys. I will do the 90% SoC charge starting tonight.

In my opinion, doing a range (100%) charge two or three times in a row is worth much more then the 10, 90% charges. It's all about balance and calibration.

 

[ModelS4Taos]

In my opinion, doing a range (100%) charge two or three times in a row is worth much more then the 10, 90% charges. It's all about balance and calibration.

After following this thread since the beginning, I have to agree with this statement. It seems to be the case with all the forums I follow (Leaf, I-Miev). The Model S, leaf and I-Miev all spend a lot of time balancing at 100%. In other words, once a car is at 100% it can stay there for over an hour before it stops charging - because it is balancing. In the case of the I-Miev, Mitsubishi sent a notice to all of their customers that they should periodically take the car down to below 20%, then charge to 100% without interruption. It used to be a service item for the dealers to do during schedule maintenance, but now Mitsubishi's customers are encouraged to do it themselves so that the cars get balanced more frequently. Last time I house-sat for my friend - I had use of the I-Miev while their away - the I-Miev balanced for a hour and 20 minutes (at very low amps) at 100% before it stopped charging. Again this was the recommended maintenance procedure from Mitsubishi. Also, it is important to remember that 100% is not really 100%(4.2volts). The I-Miev's 100% is at 4.015volts, which I believe is 93%. So those of you who are balancing at 90% may actually be balancing at 84%.

One thing that makes the Model S so mysterious is there is no known way to get can-bus data from the OBDII port. Both the I-Miev and the Leaf have aftermarket Bluetooth adapters which send can-bus data to an android app. This gives you data of voltage of each cell, reading of every temperature sensor, and shunt information. This takes a lot of guessing out of the equation. Until someone figure out how to access the the Model S BMS data directly it will be hard to be sure at exactly what percentage the Model S really starts balancing at. Leaf owners are already figuring out how to put MIM devices on the canbus to get more torque out of the motor, something the Model S does not need more of. :wink: Eventually someone will decode the the the Model S bus (linbus, canbus, etc.) messages and it will be better for everyone. The answers will be in the data from the car.

 

[brianman]

In my opinion, doing a range (100%) charge two or three times in a row is worth much more then the 10, 90% charges. It's all about balance and calibration.

Advice should come with warnings. This type of calibration might increase your degradation, so you have to decide how important it is to you to get "fresh, balanced" reporting.

 

[tomas]

+1. One simple tenet: absent indisputable knowledge to contrary, follow mfg.'s instructions. 90% is max of daily charge. So happens it also balances. Range charge when you need it, and only then. Yes, a few range charges might appear to balance faster, but why do it when it is not recommended?

 

[Mnlevin]

We have had our car since May 5 2013 and have nightly charged to 90%. While the range has slipped a little, I believe the advice from the factory has been right. We rarely leave the car unplugged in the garage. We charge it virtually every night. I do a 100% charge about 1-2 times per month. While I hate to see my numbers drop, they haven't been that much. Currently my 90% is between 175-178 and 100% is about 198. At this point we have just under 38k on the odometer.

 

[Cottonwood]

In my opinion, doing a range (100%) charge two or three times in a row is worth much more then the 10, 90% charges. It's all about balance and calibration.

Advice should come with warnings. This type of calibration might increase your degradation, so you have to decide how important it is to you to get "fresh, balanced" reporting.

You are absolutely correct; my omission!!

My advice and practice: Only do 100% charges when you need to, don't leave the car at 100%, but don't be scared of doing a 100% charge.

I got 265 rated miles on a 100% charge when I got the car in September 2012. That dropped to about 255-257 within a year and 12,000 miles. My most recent 100% charges get me 255 rated miles at a little over 2 years and 24,000 miles. Before the slider bar, I did normal charges, normally, and then range charges when needed. Now that I have the slider, I charge to 80% for day-to-day driving, but have no qualms about doing a 100% charge before a trip. After a couple of 100% charges on a trip, I sometimes gain 1-3 miles rated range at the 100% level. My car is an early Sig P85 with its original A battery.

 

[mknox]

Try charging at 90% for 10 days. That will balance. If you don't get 5 mi back I'd be surprised. Regardless, your experience not odd, most batteries drop 5% year 1 then little thereafter.

Consider yourself surprised. I switched back to 90% over a month ago and saw a 3 mile improvement. (I get 218 miles @ 90%, A-pack, 35,000 miles)

 

[hans]

Until someone figure out how to access the the Model S BMS data directly it will be hard to be sure at exactly what percentage the Model S really starts balancing at. Leaf owners are already figuring out how to put MIM devices on the canbus to get more torque out of the motor, something the Model S does not need more of. :wink: Eventually someone will decode the the the Model S bus (linbus, canbus, etc.) messages and it will be better for everyone. The answers will be in the data from the car.

Otmar has figured out some Tesla linbus commands as part of his stretchla project. He's the guy to do it.

Parts, Seat and LIN Hacking, Video Update #3 | Stretchla Blog

 

[AmpedRealtor]

After following this thread since the beginning, I have to agree with this statement. It seems to be the case with all the forums I follow (Leaf, I-Miev). The Model S, leaf and I-Miev all spend a lot of time balancing at 100%. In other words, once a car is at 100% it can stay there for over an hour before it stops charging - because it is balancing. In the case of the I-Miev, Mitsubishi sent a notice to all of their customers that they should periodically take the car down to below 20%, then charge to 100% without interruption. It used to be a service item for the dealers to do during schedule maintenance, but now Mitsubishi's customers are encouraged to do it themselves so that the cars get balanced more frequently. Last time I house-sat for my friend - I had use of the I-Miev while their away - the I-Miev balanced for a hour and 20 minutes (at very low amps) at 100% before it stopped charging. Again this was the recommended maintenance procedure from Mitsubishi. Also, it is important to remember that 100% is not really 100%(4.2volts). The I-Miev's 100% is at 4.015volts, which I believe is 93%. So those of you who are balancing at 90% may actually be balancing at 84%.

One thing that makes the Model S so mysterious is there is no known way to get can-bus data from the OBDII port. Both the I-Miev and the Leaf have aftermarket Bluetooth adapters which send can-bus data to an android app. This gives you data of voltage of each cell, reading of every temperature sensor, and shunt information. This takes a lot of guessing out of the equation. Until someone figure out how to access the the Model S BMS data directly it will be hard to be sure at exactly what percentage the Model S really starts balancing at. Leaf owners are already figuring out how to put MIM devices on the canbus to get more torque out of the motor, something the Model S does not need more of. :wink: Eventually someone will decode the the the Model S bus (linbus, canbus, etc.) messages and it will be better for everyone. The answers will be in the data from the car.

What hard evidence is there that the Model S balances anything at 100%? Someone posted a response from Tesla about this some time ago. Basically Tesla said that pack balancing is something that occurs in the background and that charging to 100% is not a trigger for pack balancing. The extended time charging at low amps after hitting 100% is basically filling the batteries to the absolute maximum. As you get closer and closer to the top of the battery, you must reduce the current in order to not overcharge and damage an individual cell. Elon's analogy is filling a glass of water. You can set the faucet on full in the beginning, but as the glass gets closer to the rim you must slow down the faucet's rate of flow in order to avoid the water from overrunning the glass. This is otherwise known as the taper curve.

Pack balancing is an internal process that happens in the background, with no user accessible trigger point, and it does not require additional current from the wall to do its job. The trickle charge after hitting 100% is simply a reduction in current to keep the cells from "spilling over" as they fill up to the very, very top of their range. The issue with the range algorithm not displaying the correct range is a calibration issue, which requires running the car from 100% to below 20% and then charging back up to 100%. This retrains the algorithm to better estimate the top and bottom range of the battery, but is also not good for the battery's long term health. This is straight from Jerome Guillen.

Apple recommends fully charging and discharging its laptops once a month in order to keep the charge indicator accurate. I believe the Model S is no different in this regard and it has nothing to do with balancing.

 

[tomas]

Consider yourself surprised. I switched back to 90% over a month ago and saw a 3 mile improvement. (I get 218 miles @ 90%, A-pack, 35,000 miles)

No, not surprised. My advice was not for you, it was for a specific person who cited specific facts.

 

[scaesare]

Pack balancing ... does not require additional current from the wall to do its job. The trickle charge after hitting 100% is simply a reduction in current to keep the cells from "spilling over" as they fill up to the very, very top of their range.

I'm not sure what you are trying to describe here.

Balance appears to occur via bleed resistors that can drop the charge of individual modules (aka "bricks"), down to the level of the others, thus balancing them. As this is bleeding charge off to the lowest brick, current form the wall is supplied to bring them all up as they fall in to balance.

The current is reduced, as it's necessary to supply the lower modules at a reduced rate so as to match the bleed rate of those modules already at a max SOC.

 

[tomas]

OK, I know this won't stop the conjecture and debate, but hopefully will help the non-EE types (like myself) who just want instructions.

We have only 2 things to rely on: recommendations from Tesla Motors, and experiential data.
Tesla recommends: range charge only when you need it, do daily charge at any level 90 or less, but don't be afraid to charge to 90 on a regular basis, + plug in whenever you can
Experience indicates: there are two things that pretty conclusively improve rated range 1) charging to 90% or more on a regular basis, 2) draining to 20% or less and charging up to 100%
I personally do not do the latter, because I seldom have need to use a range charge. Since I know I can always "restore" rated range by a few weeks of 90% charging, I would not do a gratuitous range charge.

Those who think they know how the BMS works are welcome to theorize all they wish, but until we get a Tesla charging manual or the BMS code gets released, it is all guesswork. Educated guesswork by some pretty smart people I'm sure, but still guesswork. If I've got to guess: it is balancing (vs. calibrating) at 90. That's because I've had months of NEVER draining to less than 50, and charging to 90 still seems to restore range.

PS, someone recently posted that they do 100% charges at superchargers. I do not and would not. It defeats the purpose of a quick charge. The sweet spot (in terms of a large and quick charge) is probably 10 to 80%. The supercharger is ramped down to such a low rate of charge as it approaches 100% that it defeats the purpose of the supercharger.

 

[AmpedRealtor]

Just to remind everyone of what Jerome Guillen had to say about this thread subject:

A senior tesla executive's comforting answer to concerns re:

 

[djp]

We have only 2 things to rely on: recommendations from Tesla Motors, and experiential data.

We also have professional advice from an academic with a deep understanding of battery chemistry, and industry studies on battery lifespan, which recommend the lower the SOC the better for battery longevity.

Why do Li-ion Batteries die? And how to improve the situation?

 

[mknox]

No, not surprised. My advice was not for you, it was for a specific person who cited specific facts.

I assumed your response was in reply to SteveS0353 who had been charging to 70% which was exactly what I had been doing. Only difference is his car would be newer with fewer miles than mine. Do you think it's something to do with the generation of battery pack in the car?

 

[WarpedOne]

We also have professional advice from an academic with a deep understanding of battery chemistry, and industry studies on battery lifespan, which recommend the lower the SOC the better for battery longevity.

We do have that, but we don't know exactly which battery voltage corresponds with 265 miles rated range. Is it 3.98, 3.99, 4.00, 4.01, 4.1 or 4.2?
Is it at 1 second after charging end, 10 seconds after that or 10 minuts after that? Cell voltage drops quite a bit in 'short time' after end of charging.

What cell voltage translates into "Charge now"? What voltage translates into 100miles RR?
How does voltage drop with discharging? Is it liner, superlinear, some other "curve relation"?
This and much more details we just don't know. Much of those detail change with slight chemistry "improvements" that are being made through time. Some of those details change with cells aging, and all of them differ between different cells.

That is why I continue to repeat that that range display is no better than Leaf' GOM - Guess-O-Meter.
What Tesla should not do is they should not pretend they know the current capacity of the pack down to 1/300 accuracy.
If they reduced that fake accuracy that down to only 2% steps people would be much less upset about that 1 mile range drop.