Decreasing rated range.

[qwk]

For the first time ever, I purposely ran my battery down to 0 rated miles. I plan to charge to 100% tonight to see what my max capacity is. However, we all know with 5.6+ firmware that there is capacity "hidden" after 0 rated miles. Using visiabletesla (great app) I see that I still have 8% left, which should be about 6.8kWh.

1/ Does anyone with experience trying to force the car to rebalance know if it makes a difference charging from a starting point of 8% vs ~1%? I'm willing to drive the car around the neighborhood to get the SOC lower. I've charged to 100% before (from 50-70%) and my max rated range is still degraded.

I don't think it it will matter. For the roadster it was driving it on a single key turn to 30% of charge left, which is way more than the 8% you mention. Driving it that low on charge will do more harm than good.

 

[Dave EV]

I don't know where you got the 74 cells per brick. Just because each module has 444 cells(or whatever number for that matter), doesn't necessarily mean that they have an even number of cells each.

I got it from the numbers you posted and the fact that there are 6 bricks per module as confirmed through the diagnostic screen.

For sure each module does not have to have the same number of cells. But each brick does have to have the same number of cells.

 

[qwk]

I got it from the numbers you posted and the fact that there are 6 bricks per module as confirmed through the diagnostic screen.

For sure each module does not have to have the same number of cells. But each brick does have to have the same number of cells.

I never posted that there were 74 cells per brick. There really isn't a "brick" per say, as there was in the roadster, just cells wired in both series and parallel.

 

[bluetinc]

Your welcome.

The problem with a simple voltage calculation is that rated range is a complex calculation, that takes multiple inputs into account. Nobody but Tesla engineering knows how rated range is calculated. On top of that, it's constantly changing, so that makes it impossible to come to any meaningful conclusions.

I'm not sure what you mean when you say we can't use rated range to talk about energy just because there is some complexity to how a rated number is generated inside the car to display to the driver.

The amount of energy to drive one mile under the EPA test is defined by Tesla, along with the EPA and it is a set energy unit. The number of Rated miles displayed to the user may be much more complex, but that doesn't make talking about "rated miles" as an energy unit invalid. And yes, the EPA has documented the number of kW used in 100 miles during the EPA tests, and that is a "rated mile" energy unit. That part of it is not changing with any software and it is public.


We can use Jules, or Wh, or kWh, or rated range. Yes rated ranges energy unit can vary a bit (~302 on newer cars, or ~306 Wh/mi on the oldest cars) and yes the cars available rated range is modified by the software to try to account for the cold battery and warming, but I don't think that has any bearing in this case. Isn't the question simply: If the battery is out of balance, how much does that reduce the range displayed by? In this case it's about half a volt on pack voltage. If you want to accurate to within a few percent, you can take that is that voltage on top of the pack range.

If you want to attempt to be more accurate, you can take pack capacity ~80kWh * .576/110.4 =~ 417Wh. If it makes you feel better you can then choose your own favorite rated/ideal mile energy unit, or none at all. Of course, I trust my understanding rated mile energy units more than any pack capacity calculations, but that's just me.

If you are really looking for issues with my simple voltage -> energy calculation you should point out that a battery doesn't hold the same amount of energy per volt thorough it's range. While true, the amount of energy at the top and bottom of the voltage range is the smallest, and would only server to reduce the impact of the pack being out of balance.

I have noticed that the biggest factor that goes into rated range is pack battery temperature. With FW 5.8, the car reports much lower rated miles when the Temps are below 32*F, but this does not necessarily mean that the vampire load is higher at those temps. Unfortunately there is not a way to measure this accurately, because even if you use a dedicated meter, the pack heater will take significant energy to warm the pack before it will start charging. I guess what I'm trying to say is, the vampire loads appear to be the same regardless of temps, BUT the rated range reported is lower when it's cold, because of the rated range calculation algorithm.

Again, while true, I'm not sure why this has any effect on talking about balancings effect on range.

 

[djp]

I never posted that there were 74 cells per brick. There really isn't a "brick" per say, as there was in the roadster, just cells wired in both series and parallel.

The cells wired in parallel can be considered a "brick", same as the Roadster. If there are 444 cells per "sheet" and six bricks per sheet then that implies 74 cells per brick on the 85kWh pack.

I agree each brick should have the same number of cells, otherwise some bricks would be stressed more than others.

Based on the pack voltages it appears the architecture is:

85kWh: 16 sheets x 6 bricks x 74 cells

60kWh: 14 sheets x 6 bricks x 60 cells

Model S Battery Voltage?

 

[agileone]

I have a 60 kWh pack that was showing ~ 170 on a standard charge. Tried several range charges over the past several weeks and it charged to 193. It was somewhat disconcerting. Today, I took it to the supercharger in Greenwich CT and sat there for 1.5 hours. Interestingly, the pack is now balanced. Did a range charge and it went to 206 rated miles. Probably would have gone to 210 - but charging slows considerably as the pack reaches capacity. Have had the vehicle since March 1 2013. With the exception of several campgrounds and supercharger visits, it is charged at 12 amps/110 v. At the SC, it was charging at or above 120 kWh at times.

Thanks for all your contributions. Now, if they can only fix the “vampire drain” issue on the 60 kWh….

Iz, under what conditions do you do your charging : inside/outside ? temp ?

Giving me hope, because i am getting the same low numbers on standard charges since a few months, on my 60kWh, that is a week older than yours ...

 

[Iz]

Iz, under what conditions do you do your charging : inside/outside ? temp ?

Giving me hope, because i am getting the same low numbers on standard charges since a few months, on my 60kWh, that is a week older than yours ...

Hi agileone, the vehicle is outdoors. Temperatures here have ranged from 1 - 32 F over the past several weeks. Past few days under 20 F. It appears that once the charge is complete, there is an ongoing drain to keep the battery warm as well as other processes ("vampire load"). Not certain how much shore power is used. After returning from the SC Tuesday, evening the vehicle was left unplugged and lost about 18 miles in a 12-hour period. Temps were ~ 15 F.

 

[walla2]

My December 2012 Sig with A battery at 4500 miles got a range charge last week of 257. I almost always charge at 5 - 10 amps on a 240.

 

[aviators99]

My December 2012 Sig with A battery at 4500 miles got a range charge last week of 257. I almost always charge at 5 - 10 amps on a 240.

Is this the original ("A") battery?

 

[tomas]

My December 2012 Sig with A battery at 4500 miles got a range charge last week of 257. I almost always charge at 5 - 10 amps on a 240.

I just got range charge of 252, dec 2012 p85 a battery 13k mi.
I'm waiting to see what spring numbers are. As recently as august I was getting 265. Which tells me drop is either a) weather related, b) software related, c) balancing, or d) a sudden vs gradual degradation. Degradation seems the least likely because I would expect it to be gradual. Though I admit I know zilch about battery physics.

- - - Updated - - -

Is this the original ("A") battery?

That's what walla said!!!

 

[brianman]

That's what walla said!!!

I think he was asking for confirmation that this was his original/first battery, not just whether it was A labelled.

 

[aviators99]

I just got range charge of 252, dec 2012 p85 a battery 13k mi.
I'm waiting to see what spring numbers are. As recently as august I was getting 265. Which tells me drop is either a) weather related, b) software related, c) balancing, or d) a sudden vs gradual degradation. Degradation seems the least likely because I would expect it to be gradual. Though I admit I know zilch about battery physics.

- - - Updated - - -


That's what walla said!!!

Actually, it was hard to tell, because he said, "with A battery at 4500 miles" (as opposed to "with an A battery at 4500 miles").

 

[rlang59]

Actually, it was hard to tell, because he said, "with A battery at 4500 miles" (as opposed to "with an A battery at 4500 miles").

According to the battery table in the wiki it is.

Battery table - Tesla Motors Club - Enthusiasts & Owners Forum

 

[qwk]

I'm not sure what you mean when you say we can't use rated range to talk about energy just because there is some complexity to how a rated number is generated inside the car to display to the driver.

The amount of energy to drive one mile under the EPA test is defined by Tesla, along with the EPA and it is a set energy unit. The number of Rated miles displayed to the user may be much more complex, but that doesn't make talking about "rated miles" as an energy unit invalid. And yes, the EPA has documented the number of kW used in 100 miles during the EPA tests, and that is a "rated mile" energy unit. That part of it is not changing with any software and it is public.


We can use Jules, or Wh, or kWh, or rated range. Yes rated ranges energy unit can vary a bit (~302 on newer cars, or ~306 Wh/mi on the oldest cars) and yes the cars available rated range is modified by the software to try to account for the cold battery and warming, but I don't think that has any bearing in this case. Isn't the question simply: If the battery is out of balance, how much does that reduce the range displayed by? In this case it's about half a volt on pack voltage. If you want to accurate to within a few percent, you can take that is that voltage on top of the pack range.

If you want to attempt to be more accurate, you can take pack capacity ~80kWh * .576/110.4 =~ 417Wh. If it makes you feel better you can then choose your own favorite rated/ideal mile energy unit, or none at all. Of course, I trust my understanding rated mile energy units more than any pack capacity calculations, but that's just me.

If you are really looking for issues with my simple voltage -> energy calculation you should point out that a battery doesn't hold the same amount of energy per volt thorough it's range. While true, the amount of energy at the top and bottom of the voltage range is the smallest, and would only server to reduce the impact of the pack being out of balance.



Again, while true, I'm not sure why this has any effect on talking about balancings effect on range.

In simple terms what I was trying to say is that the rated range display is a guess-o-meter. Its far better than the Leaf's, but it still isn't exact(remaining battery capacity is very difficult to measure accurately). Trying to get a sense of battery degradation, or comparing different Model S batteries from rated range displayed, is akin to pissing into the wind.

- - - Updated - - -

The cells wired in parallel can be considered a "brick", same as the Roadster. If there are 444 cells per "sheet" and six bricks per sheet then that implies 74 cells per brick on the 85kWh pack.

I agree each brick should have the same number of cells, otherwise some bricks would be stressed more than others.

Based on the pack voltages it appears the architecture is:

85kWh: 16 sheets x 6 bricks x 74 cells

60kWh: 14 sheets x 6 bricks x 60 cells

Model S Battery Voltage?

So how do you explain the 60kwh pack configuration? The math simply doesn't work for equal "brick" counts.

The reason that I didn't post exactly how the battery was wired, is because the answer is, I don't know for sure. I haven't completely taken one apart, yet.

 

[Iz]

I just got range charge of 252, dec 2012 p85 a battery 13k mi.
I'm waiting to see what spring numbers are. As recently as august I was getting 265. Which tells me drop is either a) weather related, b) software related, c) balancing, or d) a sudden vs gradual degradation. Degradation seems the least likely because I would expect it to be gradual. Though I admit I know zilch about battery physics.

Agree. Degradation seems to be less likely at this point. I just balanced my 60 kW pack this week. However, due to weather and perhaps software, there is a drop in range throughout the day and while driving. Some can be attributed to having the heater on (I keep it low). Seems the cold weather just zaps the battery somewhat. The black box in all this is perhaps software and what routines are implemented to keep the battery warm (temperatures, cycle time).

 

[djp]

So how do you explain the 60kwh pack configuration? The math simply doesn't work for equal "brick" counts.

The reason that I didn't post exactly how the battery was wired, is because the answer is, I don't know for sure. I haven't completely taken one apart, yet.

I don't know the exact configuration either, I'm just making some educated guesses based on what we know about the pack voltages, the diagnostics screen, and the Roadster. I'm also assuming the 85 and 60 use the same 3.1Ah capacity cells, which I think is a pretty good assumption, but could be wrong.

The math works:

60 cells/brick * 6 bricks/sheet * 14 sheets * 3.1Ah/cell * 3.86V nominal / 1000 = 60.3kWh

74 cells/brick * 6 bricks/sheet * 16 sheets * 3.1Ah/cell * 3.86V nominal / 1000 = 85kWh

 

[tomas]

In simple terms what I was trying to say is that the rated range display is a guess-o-meter. Its far better than the Leaf's, but it still isn't exact(remaining battery capacity is very difficult to measure accurately). Trying to get a sense of battery degradation, or comparing different Model S batteries from rated range displayed, is akin to pissing into the wind.

Yes but a mild wind. As compared to my BMW X1, which can calculate as many as 450 miles or as few as 250 miles remaining on an identically full tank. I guess we are just more sensitive to the wind because charging is not yet ubiquitous. :wink: I am with you in suspecting that it is more algorithm than degradation. I hope one of the geniuses on this forum figures out how to prove cause so we know for sure.

 

[hans]

I have a 60 kWh pack that was showing ~ 170 on a standard charge. Tried several range charges over the past several weeks and it charged to 193. It was somewhat disconcerting. Today, I took it to the supercharger in Greenwich CT and sat there for 1.5 hours. Interestingly, the pack is now balanced. Did a range charge and it went to 206 rated miles. Probably would have gone to 210 - but charging slows considerably as the pack reaches capacity. Have had the vehicle since March 1 2013. With the exception of several campgrounds and supercharger visits, it is charged at 12 amps/110 v. At the SC, it was charging at or above 120 kWh at times.

Interesting that the range charge (100% charge) on the DC Supercharger balanced your pack successfully while several attempts to do the same via AC sources and the charger(s) in your car did not. I wonder if the firmware or BMS with the onboard charger in the loop is not as capable at balancing the pack.

Of course it could just be that repeated attempts to balance via range charges just happened to result in success when you were on a SuperCharger.

Has anyone else tried to balance a "degraded" pack on a SuperCharger just to see if it's better at the task? Not that we need SuperCharger stations full of trickle charging owners (that would be bad) but it might be an interesting experiment to try once or twice.

 

[Denarius]

Interesting that the range charge (100% charge) on the DC Supercharger balanced your pack successfully while several attempts to do the same via AC sources and the charger(s) in your car did not. I wonder if the firmware or BMS with the onboard charger in the loop is not as capable at balancing the pack.

Of course it could just be that repeated attempts to balance via range charges just happened to result in success when you were on a SuperCharger.

Has anyone else tried to balance a "degraded" pack on a SuperCharger just to see if it's better at the task? Not that we need SuperCharger stations full of trickle charging owners (that would be bad) but it might be an interesting experiment to try once or twice.

I recently ranged charged at home to 253 prior to a road trip, on my way back I did a range charge at a supercharger and after waiting for charging to completely finish I was at 252, so I don't think the supercharger is doing any better at balancing.

 

[walla2]

Yes. It is my original A battery. It's my super battery. The one that I've been told by Tesla techs seems to have a bit more beast mode/go in it. Sorry for the confusion.

I'll find out if the extra power is true this spring at the drag strip in town.