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Had the opportunity to do another range charge this morning. It finished at 245, up from 244 last month.
One thing I still don't understand is the balancing. Unlike the previous range charge, I watched this one closely on the mobile app. I saw it hit the "1 min remaining" mark at 245 miles. It must be balancing now, I thought. The charger power hovered between 1-3 kW during the next hour. When it was finally finished, the balancing had added a grand total of (drum roll).... 0 rated miles! It still had 245, exactly as it did before entering the balancing period.
Where did this power go? I don't see how the car can still be pulling power and not be adding range to the pack. Balancing should only increase your max range by pushing charge around the cells to those that are at a slightly lower voltage. But, alas, that is not what happened today.
One thing I still don't understand is the balancing. Unlike the previous range charge, I watched this one closely on the mobile app. I saw it hit the "1 min remaining" mark at 245 miles. It must be balancing now, I thought. The charger power hovered between 1-3 kW during the next hour. When it was finally finished, the balancing had added a grand total of (drum roll).... 0 rated miles! It still had 245, exactly as it did before entering the balancing period.
Where did this power go? I don't see how the car can still be pulling power and not be adding range to the pack. Balancing should only increase your max range by pushing charge around the cells to those that are at a slightly lower voltage. But, alas, that is not what happened today.
This seems to be normal behavior. That's why it takes several range charges to recalculate/balance the pack.
On another note, my car never says 1 minute remaining. It goes from 5 minutes remaining straight to calculating charging time. I have had the "calculating charging time" remain on for around an hour before the charging was completed(range charge).
islandbayy
Active Member
Higher voltage cells may be being depeleated to bring them to the voltages of lower voltage cells. And more power may be added to the lower voltage cells. Also, the car is recalculating total capacity during this time (cant confirm that, but based on my experiences with EV's in general). It may be that the computer has mis-calculated the capacity of the pack due to being out of balance. Despite what most think. it really is somewhat of a "Guess" that the computer is doing to give a range number. All it is is a Estimate, and all the computer can do is try and make the estimate as accurate as possible.
Right, but that estimate is based on an actual measurement of the pack voltage. If it spends an hour pulling 1-3 kW, the pack voltage should only increase as those lower voltage cells are brought up on par with the other cells that are maxed out. I don't know, maybe I'm missing something.
@qwk - why does it take several repeated range charges to balance a battery? I mean why can't the BMS just get it right the first time around? It just comes down to equalizing cell voltages, pure and simple, and I don't see why that would have a dependence on the number of successive range charges.
islandbayy
Active Member
Only Tesla can really answer that one. But I will provide my Opinion.
In my Opinion, they "may" have limited the balancing to a shorter time period, as people don't want to wait forever for it to finish.
I thought I'd throw my 10 cents in here; I have definitely seen rated range decrease, I'm at 19k and can count on one hand the number of range charges I have ever done.
After reading the thread and consulting with the service center, I decided to experiment:
1) Disable scheduled charging. This seems to prevent balancing.
2) Do a single range charge to recover capacity
I did see an improvement with #1, although minor. #2 didn't add much, but at one point when it was balancing (clearly) I had to stop it prematurely.
This is mostly conjecture on my part but would be interesting to get other thoughts on what works/doesn't.
After reading the thread and consulting with the service center, I decided to experiment:
1) Disable scheduled charging. This seems to prevent balancing.
2) Do a single range charge to recover capacity
I did see an improvement with #1, although minor. #2 didn't add much, but at one point when it was balancing (clearly) I had to stop it prematurely.
This is mostly conjecture on my part but would be interesting to get other thoughts on what works/doesn't.
FredTMC
Model S VIN #4925
Yes, I had a similar experience a few days ago. I Range Charged and it finished at 196 (a new low for me). It balanced for about an hour while at 196 and didn't increase at completion. HOWEVER, I then immediately drove the car and I went 3 miles before the rated range decreased to 195. Another fact is that these 3 miles averaged over 600wh/mi due to hills.
Bottom on line is that I think the energy taken in during battery balancing wasn't reflected/accounted in the displayed "rated range" of 196 when charging was complete.
I'll have to see if my rated range improves next time I range charge...
As part of my efforts to meet the #DriveFree team, I did two back to back range charges. The first one ended at 190 miles, the second at 194 (even though the battery was colder). So I think the added range from balancing is not reflected after the first charge, but only after there has been some discharging, so the algorithm can compare energy extracted against the voltage based SOC estimate.
FredTMC
Model S VIN #4925
I did 3 range charges over 1week and my 90% is up 4 mi (215mi) and I saw 245mi at 100% on my last full charge (was 242 when I left last Friday, but for over 1 hr)
the first range charge drove down to 8 mi and last one down to 4 mi remaining but I added at least 30kW when I was near 80 mi remaining so it wasn't a direct drain from 100 to ~12%
..one more full charge ended at 246 mi last night
the first range charge drove down to 8 mi and last one down to 4 mi remaining but I added at least 30kW when I was near 80 mi remaining so it wasn't a direct drain from 100 to ~12%
..one more full charge ended at 246 mi last night
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S85. Car charged to 240 rated miles @ 90% at 5k miles with older firmware during fall 2013. Now at ~195 rated miles @ 80% at 12k miles in midst of Northwest winter. Decided to do a range charge this morning before a 60-70 mile outing. Here is my experience so far
2/2 10am 254 mi/99% (wife couldn't wait for the last 1%. Battery charging was down to about 1kW on VisibleTesla)
When I took the car for a 60-70 mile drive. It stayed at 254 miles for almost 10 miles until I started climbing some hills. I do have a big down hill near my house but regen wouldn't allow too much charge due to a nearly full battery pack.
Drove about 60-70 miles. Returned home and put it on charger with 81% charge limit.
2/2 02pm 196.3 mi/81%
If I use a calculator 196.3/.81 = 242 max charge
======
So a couple of interesting observations
1. Can't extrapolate my 81% charge rated miles for full charge rated miles. I was able to get more miles full than my extrapolated calculation.
2. There seems to be a few more invisible miles beyond my 254 rated miles @ 99% full charge.
My understanding is range charge isn't bad if you use it right away so I plan to range charge a few times next few weeks just before driving some reasonable distance to collect more data.
2/2 10am 254 mi/99% (wife couldn't wait for the last 1%. Battery charging was down to about 1kW on VisibleTesla)
When I took the car for a 60-70 mile drive. It stayed at 254 miles for almost 10 miles until I started climbing some hills. I do have a big down hill near my house but regen wouldn't allow too much charge due to a nearly full battery pack.
Drove about 60-70 miles. Returned home and put it on charger with 81% charge limit.
2/2 02pm 196.3 mi/81%
If I use a calculator 196.3/.81 = 242 max charge
======
So a couple of interesting observations
1. Can't extrapolate my 81% charge rated miles for full charge rated miles. I was able to get more miles full than my extrapolated calculation.
2. There seems to be a few more invisible miles beyond my 254 rated miles @ 99% full charge.
My understanding is range charge isn't bad if you use it right away so I plan to range charge a few times next few weeks just before driving some reasonable distance to collect more data.
The relationship between rated miles and SOC is not linear, but approximately quadratic (it looks like a bow). I have no idea why. I would've calibrated the SOC calculation in such a way that rated range is linearly proportional to SOC.
If VisibleTesla has a logging function, then you can graph it to see this.
If you are going to dig into the details and do your own calculations, then here are some of the details that you will need to help your numbers make sense:
The percent you are talking about is SOC which is the State of charge of the battery. This is almost directly proportional the pack voltage range with temperature correction. The voltage of a battery is not perfectly linear to the amount of energy stored.
A displayed 0 range left is not equal to a 0% SOC, on my car it seems to be about 8%.
As the cars range is decreased, a small number of Wh are hidden from the driver and "stored" to have some remaining range below "0" rated miles.
There is a cold temperature adjustment (which starts somewhere around 40-50F) that reduces the displayed range to account for the warming needed in cold weather.
Peter
PS, a minor side note, when you mention 240 miles on a standard 90% charge, are you sure about that? Standard use to be 93% which would give owners ~240-246 rated miles, and Tesla changed what a standard charge is to reduce it to 90% which puts new cars in the low 230s.
The percent you are talking about is SOC which is the State of charge of the battery. This is almost directly proportional the pack voltage range with temperature correction. The voltage of a battery is not perfectly linear to the amount of energy stored.
A displayed 0 range left is not equal to a 0% SOC, on my car it seems to be about 8%.
As the cars range is decreased, a small number of Wh are hidden from the driver and "stored" to have some remaining range below "0" rated miles.
There is a cold temperature adjustment (which starts somewhere around 40-50F) that reduces the displayed range to account for the warming needed in cold weather.
Peter
PS, a minor side note, when you mention 240 miles on a standard 90% charge, are you sure about that? Standard use to be 93% which would give owners ~240-246 rated miles, and Tesla changed what a standard charge is to reduce it to 90% which puts new cars in the low 230s.
Yes, I read about 0 = 8% remaining. Didn't know about the cold temp adjustment.
Thanks for the note, you are probably correct. I remember reading standard charge used to be 93% on old firmware on another thread which make sense now why I saw ~240.
Its clear SOC isn't linear to rated miles so no way to do simple linear extrapolation like I did.
Does everyone believe imbalanced pack on higher mileage cars running the latest firmware is the main reason we see lower rated range? Newer loaner cars with latest firmware seem to not exhibit this problem. Some range charge effort seems to recover more rated range.
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