Just throwing this out, would it be better to limit the 40kw packs to the top portion of the pack? What I mean is that the 40kw cars would use the capacity from 20-60kw vs 0-40kw.
In terms of battery life, my opinion would be to limit the back in the middle. Don't give all the way to the bottom, and don't give all the way to the top. Say, stop the pack at approx 20% from the bottom, so the pack is never DEEP discharged, and then limit the top end to 90%ish, that way it is NEVER sitting at 100%. That would be a ideal range to provide approx 40kW.
The ONLY reason I think they are not doing this, in my opinion is as follows.
Say, someone runs their "40" down to nothing and the car stops driving. Now, that person would be on the phone complaining to tesla "why" can't I use the remaining 20% to get home, or "why" cant you unlock it "just this once" to let me get off the freeway and to a charging station etc... By limiting it to the bottom end, they are saving their phone support many headaches on that.
Now, Idea time, if they limit it how I said above, LET them use the remaining 20%, BUT limit the overall kW output. we already know the car can limit output at low SOC, why not let them then use the last 20%, but limit the car to say, 25 or 30kW. I've already hit that low on my 60 when running on "fumes", yah, you "could" get er up to freeway speeds, but it would take a hell a long time to get to freeway speeds, and then all it takes is a gust of wind and your slowed wayyy down. Limiting to 25 or 30kw would make the car impractical for continued use accept to get the car to a safe place/place to charge, Like a LIMP Mode. (Yes, I know that was a massive run-on sentence).
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Third max range charge in about 5 days....I only got 190 miles this time so I lost a mile possibly
I think islandbayy is the exception more than the rule when it comes to battery degradation.
So far, with quite a number of people I've talked to in private to help solve issues (both with battery balancing, and other vehicle related issues), I am definitely not the exception.
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Yes, if Tesla were to make that suggestion that would be very bad and a good way to make an anti-customer. That was why I was suggesting it
and really only if it was something he was considering anyway. Like if he felt that the 40's range wasn't enough for his actual usage and/or he underestimated his daily usage. Meaning he has an "out" for getting more range that us 60 owners don't have. Not trying to stir things up, just trying to be helpful.
The range my 60 has at max charge has not changed appreciably, but I don't think that it is anything unique to my 60 or islandbayy's 60. I suspect it is just how they are being used. Keep in mind, just a couple of months ago Islandbayy was reporting that he couldn't get more that 192 miles from a range charge. Now a few months later he is getting up to 208. So to me that says this is not a permanent degradation issue. I think (could be wrong) that mostly is related to temperature and balance of the pack. Islandbayy certainly does not baby his pack. He full cycles it often (large depth or charge) which should put the most wear on his pack. It may be that this type of usage is actually better for keeping it in balance. Or, it maybe just doing a range charge at a supercharger that is making the difference.
I don't expect anyone here reading this to do anything to their cars such as range charge or balance or anything. I say these things for discussion purposes. I will however, put my money where my mouth is and do this experimenting on my own car.
For those who are having real issues with their cars and don't want take amateur advice from us on TMC, they really should go to Tesla for this. And if we are lucky, they will share what they have learned.
Update:
As you can see, Islandbayy's 60 is not unique. I am at 14,500 miles and still get a 203mile range charge at -2*F. I suspect it will do better when it warms up and with a little bit more balancing.
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Quite correct where a few months ago I couldn't get it over 192 on a range charge. It was 100% temperature related. I remember us and Montgom discussing that at the Chancery
It was the poor range charge that got me experimenting on the SPECIFICS that effect the range of the Model S, and how the Model S handles Temp changes, balancing etc...
I experimented quite a bit with both outdoor temps and indoor temps at my shop, to discover where the big "hits" come from in cold temps. In fact, in theory, I should be able to exceed my original delivery range of 209 if I get my car in temps of 100*F +. It should theoretically go up to about 213ish, maybe more!
And yes, I beat the living crap out of my pack, at least, compared to most people. I push this thing to it's absolute limits!
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I have not read this whole thread, so I hope I'm not repeating anything or missing a point.
I don't believe balancing cells improves overall life, meaning I don't think it reduces the rate of long term degradation, but I do believe it improves the available range at the time and would be worth doing if you need the extra range but since we don't know how the S manages this, it's currently impossible to time the charging. I don't recommend regularly deep cycling the battery with the hopes that it balances the cells accept for the times you really need to max the range. If you are pushing the battery daily to the point where you are stressing about it on a 40 kW S, I'd highly recommend unlocking the 60kW ability. The folks on the Leaf forum who were constantly deep cycling to test capacity were ironically the one's who appeared to see the fastest long term degradation. The Leaf is a different beast, it doesn't have TMS and likely allows more of the packs capacity to be accessed, but still, I think it is worth erring on the side of caution even with the S. the effect of ambient temperature on capacity has been tracked carefully on the Leaf forum. most of the losses experienced during winter, recover with the warmer weather. While the S does have temperature management, the battery is subject to ambient temps most of the time. from what I've seen, it appears the TMS doesn't kick in unless at the extremes. some warming appears to happen during preconditioning of the car but I'm pretty sure the battery is still effected by ambient temps. warming up the battery before range charging would likely improve the short term capacity. Unfortunately we have no temperature gauge to monitor. I would suggest that it's very difficult with the S to find an apples to apples basis on which to be absolutely sure how much the fluctution in rated range is due to ambient temps vs cell imbalance vs long term degradation. If your garage is conditioned, and the S sits there long enough to "cold soak" the battery to the ambient temperature and you do all the kind of scientific controls that Tony Williams did for the Leaf, then you might be able to nail it down with certainty but wow, it's a lot of work with such a large battery and so many variables that are hard to control.
To max out the range on the Leaf, I would use the prewarming function to heat up the car for sometimes, a couple of hours, then top off the charge one last time, then drive as far as I could without the climate control on. The Tesla S should warm the battery at least some with preconditioning. I would also drive the Leaf very conservatively and on rare occasion in the winter I'd even take along rechargable chemical heat packs to keep my feet warm and eliminate climate control use. fortunately the Tesla S has a much more efficient heater than the 2011/12 Leafs.
As the battery ages and/or if not conditioned and you want to max out the range predictably (down to the mile or your destination), you need to drive in such a way as to consume a consistent MPkW or WPM and adjust the speed by slowing down when you go up hills, accurately keeping the energy draw consistent, calculate periodically to see if you are within range of your destination and adjusting accordingly ... especially important in the winter!
I got pretty burned out paying so much attention to range with the Leaf and decided the 85 kW battery option for the S was worth it's weight in gold... I almost never think about it. It's very important that people factor in the seasonal cycling of range and long term degradation when considering which pack to include with the order of the S. A larger battery allows for more shallow, mid pack cycling, and I'm quite convinced that that will help long term life of the battery, even if it mutes cell balancing in the short run. at the very least, a larger pack gives you precious peace of mind.
the good news is, cold ambient temps most certainly improve long term life of batteries. those who see a big drop in rated range in the winter which bounces back in the spring are likely going to see longer overall life of the pack. with the Leaf, it appears that long term rate of degradation follows a pattern of altitude and latitude surely correlating to ambient temps, the further south you go, the worse it gets. It's going to take a while with the S to see if a similar pattern plays out. I expect that the TMS in the Tesla S adequately protects the pack from extreme temperatures, so we shouldn't see the accelerated, permanent dropping off of range that so many of the Leaf owners down south are seeing during summer but I think it's safe to say that cooler ambient temps will still be better for the battery long term and still tend to reduce range in the short term during cooler months.
May want to go back and read the whole thread. A balanced battery pack, DOES, increase the overall life of the cells. The lower voltage cells get discharged to a lower state of charge more often, and the higher voltage cells are kept at a Higher state of charge more often. This causes abnormal ware, and premature failure in some cells causing even more issues, as well as other problems. Grab a pot of coffee, and enjoy the thread for a hour
As for cold ambient temps improving the life of the batteries, yes and no. Lithium batteries like cool, NOT COLD. At 32*F and below, they do not "like". Will it cause many issues? No, you will loose regen. And you will have a limit on power draw. Exceed the limits on power draw(not possible with the Model S) and you can damage them. CHARGE lithium batteries when their below 32*F, and you will PERMANENTLY damage them. Thats why the Model S (and even the leaf) have a Pack heater. The car will heat the batteries to above 32*F to charge regardless of the settings. Charging lithium below freezing Will, without question, cause Permanent capacity loss (The Anode gets itself electroplated, read whole thread for more detailed explanation. It's closer to the beginning)
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I understood you were trying to be helpful, and it is appreciated.
I and others have taken our concerns to Tesla, but as far as I know, after Fremont looks at our batteries (remotely), we all get the same "battery is normal" response. Only time I ever hear any mention of "balancing" is here, never from anybody at Tesla. I will be escalating my concerns within a few days. If anybody has any suggestions re: an appropriate Tesla contact, I would very much appreciate that info.
The fact that some of you have seen essentially no degradation leaves me hopeful that this really is a balancing issue that can have a happy resolution.
As I keep saying, people do not realize how much Temps greatly impact range. Even when the packs at 50*F does the range begin to drop. But yes, Tesla needs to bring forward some help to 40 owners. I still would really like a option to balance the pack (charging screen button) that will balance at any (reasonable) state of charge.
