That is the problem with the 40kW if there is really 60kW of batteries and they only balance properly at a full charge. I think this may be the case for lithium batteries but only really have experience with 6 cell different chemistry batteries.
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Could Tesla's engineers really designed a battery pack that won't balance unless fully charged and yet still market the 40kWh pack? Can this really be?
Sorry I'm not saying that it is like that for sure but it would suck if it was. There aren't very many 40 packs maybe we'll hear some more data soon
islandbayy
Active Member
the packs will balance when not at 100%, just that charging to full makes the process quicker. I'm at a loss as without knowing their software, I can only guess.
SCW-Greg
Active Member
Our cars are from the same era, if you will (I was right behind you on the forums each of us eagerly waiting for our Model S' to arrive).
For me... 90% now = 220, 100% = 256 miles.
I'll cross 12,000 miles tomorrow. Almost 8 months.
4,046 total kW, 336 avg kW/miles
It is still winter months here (lows right now around 30, highs hitting 50 ish), and cold temps will hinder full output/range.
Otherwise flawless operation.
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I welcome your guess as to why Hans and I have 60 packs with far fewer miles than you, far fewer deep cycles than you, charge in warmer temps than you, and we both are showing max rated miles anywhere from 13-15 rated miles fewer than you. The only thing Hans (among other 60 owners showing similar numbers to mine) and I don't do that you do is regularly range charge and have deep cycles.
Even with sleep mode? My car always seems to enter sleep mode immediately upon charge completion and I don't think it can balance while asleep. But really, how long should it take to balance? 30 minutes - an hour? Why doesn't it just stay awake during this period of balancing and then fall asleep? Can you address these points in your video guide, please?
islandbayy
Active Member
Videos already being uploaded, about 22 minutes long.
battery managment system should be independent of the rest of the vehicle (in my opinion). the pack must be monitored constantly, temperatures, discharge etc... once again the problem is partially that I don't know the in depth details of how the software is setup.
Now, I really wish we had a option we could hit in the touch screen to equalize (balance) the pack. on the ev's I used to build, I had 2 nice devices (mind you that these were all lead acid batteries but outcome is the same). one device was called a pack tracker, connected to each individual battery, and reported voltages of each, to list the driver monitor for bad or worn out batteries/ cells . the next, it's been a while but I think it was called batteryEQ. also connected to each battery, and worked constantly. it would nonstop shuffle charge from the higher voltage batteries to the lower volt ones, to equalize then. now, the Model S doesall of this automatically. however, as their system is proprietary, we just don't know how this system operates on the models, how often, his long it will run for at all etc ... all we do know is that when charging to 100% soc, the BMS actuvates and starts doing the balance, and that it can take multiple times to complete this.
I hate to add more complexity to this, but if anyone is really comparing, the mileage on the car is not adequate as a data point. You need to also use the average Wh/mi in order to measure degradation. The Panasonic charts relate to number of charging cycles. If possible, we should look at (odometer * (Wh per Mile / 1000)) to get kW used. These is a big difference in Wh/mi depending on driving style and where you live. Easily up to 100 Wh/mi average difference at the extreme. I baby my car in a warm climate and my lifetime average is around 317. I'm being a bit conservative with that number because I can't tell you exactly, because Tesla keeps resetting my trip computer.
Hey, good to hear from you.
Interesting, looks like our numbers for a given SOC are pretty close @ 90% (I think I'm in your ballpark for 100% too, but I've typically only gotten to ~97-98% for my last couple of range charges, due to time constraints... it takes a while to get those last few percentage points).
Interesting that I've about 50% greater mileage than you on my pack, but we ours are about the same age. So it would appear that age or number of charge cycles might be the governing factors.
As an FYI: I charge to 60-70% during the week (the greater SOC during the cold weather) and 90% on weekends.
My lifetime Wh/mi is 315 as I have never reset my trip odometers. I live in a warm weather climate. I generally baby my battery. I would bet that Islandbayy has a Wh/mi far greater than mine since he is in Wisconsin and I believe does a lot of freeway driving and LOTS of deep cycles, as in every day. I don't see how this would impact the rated miles. Yobig also puts a lot of miles on his car, presumably freeway driving and high Wh/mi, in cold climate in NE and also lots of deep cycles.
It could be these are two outliers, but ironic that the two regular posters who have the most regular deep cycles and at least in IslandBay's case, numerous, frequent range charges, have the best numbers of anyone.
It's the way batteries work. They degrade over their lifetime based on the kWh used (cycles). If person A has a Wh/mi of 300 and person B has a Wh/mi of 600, person B will have to charge their battery completely twice as many times as person A, given the same miles.
do we know if it's limited on the lower side or the upper side? In other words, does the car only charge from 0% to max 66% and stop, or can you only discharge from 100% to 33% and it stops? In either case, given lithium ion chemistry, it's practically impossible to ever balance this pack and accurately calculate charge capacity. If you can't charge to 100%, you can't balance the pack, the cells will become very imbalanced, and you can't ever accurately calculate degradation. If you can't charge below 33%, then just the same you won't ever be able to accurately know remaining SOC. (I might be getting my terminology mixed up here, SOC, charge capacity, etc).
UNLESS they cycle the battery packs. (I think think this would be the ideal implementation). so in that case, if there are 12 packs, labeled 1-12 (making up numbers here), your current charge could be using packs 1-8, while 9-12 are unused. Therefore you can fully cycle packs 1-8 from 100% to 0%, and then at some point in it's charging cycle, Tesla might "deactivate" pack #1 and activate pack #9. This would at least allow full drain and full charge in order to accurately calculate charge capacity and rated range. Then again, what you're losing here is probably battery life, as well as performance.
If the 40kW is implemented such that the 66% that you use is between 17% and 83% of all battery packs, then your battery is going to last a VERY VERY long time at the cost of imbalanced packs and never really accurately knowing charge capacity. At least in this implementation you actually have more simultaneous power available. If I had a 40, I think I'd prefer this implementation. It's possible they would implement it this way, with some periodic charge to 100% for balancing (once per month or something) and the software just 'hiding' what it's actually doing.
Thanks for the replies, everybody.
@tdiggity - Tesla hasn't acknowledged that there is a problem. Based on my conversations with various employees, there is no way they are going to unlock the reamaining 20kwh on our batteries, even temporarily.
@islandbayy - Yes, we can set the charge level, but only to a maximum of 72%.
@SFOTurtle - Yes, I believe they would, perhaps without giving enough thought to the ramifications.
Two weeks ago, my service manager has told me that there is a new firmware upgrade coming within 2-3 weeks that will address loss of range. Perhaps a revised balancing algorithm? We'll see (I hope).
Until temperatures starting dropping here in the northeast a month or so ago, my lifetime average my lifetime kwh usage was 291 or so. Now with temperatures usually in the single digits or teens, it has risen to approximately 315 just in the last couple of thousand miles. Most of our trips are short (my wife has a 12 miles commute to work), so the battery never really has a chance to warm up thoroughly. KWh usage now usually averages over 400 for a charge.
When purchased, the car had 140 rated and 160 ideal miles, as promised. I was able to easily make a 115 mile trip with 40 or 50 projected miles remaining. Now at 118/136, I would never attempt that trip (especially during the winter) and the car is rapidly approaching not worth owning.
@tdiggity - Tesla hasn't acknowledged that there is a problem. Based on my conversations with various employees, there is no way they are going to unlock the reamaining 20kwh on our batteries, even temporarily.
@islandbayy - Yes, we can set the charge level, but only to a maximum of 72%.
@SFOTurtle - Yes, I believe they would, perhaps without giving enough thought to the ramifications.
Two weeks ago, my service manager has told me that there is a new firmware upgrade coming within 2-3 weeks that will address loss of range. Perhaps a revised balancing algorithm? We'll see (I hope).
Until temperatures starting dropping here in the northeast a month or so ago, my lifetime average my lifetime kwh usage was 291 or so. Now with temperatures usually in the single digits or teens, it has risen to approximately 315 just in the last couple of thousand miles. Most of our trips are short (my wife has a 12 miles commute to work), so the battery never really has a chance to warm up thoroughly. KWh usage now usually averages over 400 for a charge.
When purchased, the car had 140 rated and 160 ideal miles, as promised. I was able to easily make a 115 mile trip with 40 or 50 projected miles remaining. Now at 118/136, I would never attempt that trip (especially during the winter) and the car is rapidly approaching not worth owning.
Liz G
P03056
I'm right there with you guys.
I have 32,000 miles on my S, with ave Wh/mi of 330 on 1 year of driving.
When I got my car a year ago my range charge was 264. Over the summer, after a few software updates, I was getting 252 on a range charge. This winter the best I can get is 248 and that's sitting at a SC for a while waiting for it to tick up those last couple of miles. Tesla tells me that my perceived loss of range this winter is do to the updated algorithms. So, I'm going to have to wait and see if my range returns with the good weather.
In the mean time, after reading some of the comments on balancing the battery pack, I've decided to try something. Since my car will be parked at the St Louis auto show all weekend, one of the rare times it will not be driven on a daily basis, I've decided to let it range change to max on the 110 it will be hooked up to at the show. I'm hoping that the trickle charge will help balance the pack and I will see some of my range return. Fingers crossed.
Based on what the slider on the software limited 60s show I'd say it is high side limited. Their slider tops out at about 70% of a 60 but shows the rest of the slider grayed out.
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I think a big part of it is that the people that have done full discharges and recharges 100-0% and 0-100% the battery management actually knows how much charge the batteries will take. Those cars without that data are just taking a "guess".
I don't think this is true. When doing a full charge to 100% the management should be able to tell that no more power is being taken by the batteries and heat is building up instead, at least that is what seems to happen in other systems
SCW-Greg
Active Member
Hey, good to hear from you.
Interesting, looks like our numbers for a given SOC are pretty close @ 90% (I think I'm in your ballpark for 100% too, but I've typically only gotten to ~97-98% for my last couple of range charges, due to time constraints... it takes a while to get those last few percentage points).
Interesting that I've about 50% greater mileage than you on my pack, but we ours are about the same age. So it would appear that age or number of charge cycles might be the governing factors.
As an FYI: I charge to 60-70% during the week (the greater SOC during the cold weather) and 90% on weekends.
I'm driving about 60 -65 miles during the week, and maybe another 15 on the weekend. Usually charge to 80%, then after my commute, the pack sits at near 50%, until charge at 3am again. On the weekends it will usually sit for a day or two, not plugged in, at near 50% SOC.
I assume you mean 60-65 miles per day during the week? That makes the math for your total mileage work out about right. If so, that's about my commute as well. Another night or two during the week I add an extra 25 miles or so.
On weekends it varies from only 20 miles total, to a couple of hundred. When you say "another 15", is that total for the weekend... or 65+15=80 for each day?
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