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How much has your Model S' battery degraded?
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FredTMC
Model S VIN #4925
Rated doesn't take into account the car's driving style. It's the same measure for everyone
Just got off the phone with a Tesla regional manager in Cali and he told me NOT to run it to 0 and back up to 100%, as it "balances" automatically when plugged in at 90%. However, he did inform me that it might be a good idea to discharge it to about 20% and back up to 80% or 90% (not 100%).
Yes, I report my range charges as ideal miles. The rated miles differ if the car is placed in range mode or not, or dual motor vs single motor (I think ).. My car had 301 ideal moles just under three years ago... So it seems like 6% loss after almost 3 years and 85k miles.. The thing is that I have had essentially no loss over past 15 months.
I know this has been hashed out many times... But, I still don't understand it. A new car or new battery still charges up to 265+ miles and from what I've seen it's linear. So if it's still achieving the same max range I don't see how the algo could have been changed. That and the fact that it ought to be based off of the EPA number which was only released once.
No, rated miles does not adjust to you driving style. But there have been some adjustments in how the car calculates the predicts range. "Ideal miles" has never been changed so it would be a better way to compare. Problem is, no one sets their car to show ideal miles as it's not matching real world driving at all. I don't remember what my ideal miles when it was new because I never used it.
deonb
Active Member
Balancing requires that cells be held at a specific voltage and then trickle charged beyond that. It can in theory be done at any level - doesn't need to be 100%.
However, the Model S charger will NOT do this at 90%. Once the charge reaches 90%, the charging immediately stops. If any battery balancing is indeed taking place, it's not at 90%.
We do however know that once the Model S reaches 100%, the car slows charging to a trickle and it will remain in that trickle for up to 4 hours (at least what I've seen it at, others might have seen it for longer). That behavior seems more like balancing to me.
I buy that it can do algorithm recalibration at 90%, and it can do balancing at 100%. However, I don't buy balancing at 90% - not on a Model S at least. So if he used the word "balancing" at 90% rather than "recalibrating" at 90%, I would take his advice with a grain of salt.
djp
Model 3 Performance
Balancing on the Roadster "bleeds off" the highest cells after a charge completes rather than trickle charging the lowest. The Model S pack also has bleed resistors and probably uses a similar approach to balancing. It's possible to balance at any level without trickle charging.
As we have learned from people who have opened the battery pack, the balancing is done by bleeding off the higher modules. It is not done by charging the lowers one more. So balancing can take place without the charger doing anything.
That behavior is actually common when charging Lithium cells to 100%. They are charged to the point where the max voltage is achieved and then the voltage is kept constant while the current is reduced. As the battery gets closer to 100% the current needed to hold the max voltage gets smaller and smaller. This is not balancing, it is the normal way to fully charge a Lithium cell.
Look at this graph. The blue line is the voltage. It goes up to the max. Once it reaches it, it is kept constant by adjusting the current down gradually. The right side of the graph shows this well. The flat voltage curve and the dropping current curve.
deonb
Active Member
Which just stresses more that the Tesla regional manager does not really have an idea what he's talking about when he says to charge it to 90% in order to balance it... (if those were indeed his exact words).
The car either:
* Balances at 100% - circumstantial evidence being that people (including myself) see behavioral changes at 100%
* Balances at any SOC - evidenced from the wk057 disassembly
* Doesn't balance at all
Either way, there isn't a balanced-related even that happens at 90% more so than it would happen at 60%.
I admin that I don't know if what happens at that 100% plateau is actual balancing or range re-calibration. But I know what happens at 90% isn't balancing.
Top balancing requires that the higher cells be bled down until all cells are all equal voltages. This activity will lower overall pack SOC, so the charger would have to "trickle" the now-balanced pack up to 100%. On some systems, they continuously trickle charge the pack with a constant voltage and any cells that exceed the 100% threshold are bled. Charging stops when the current drops below a certain trip point and the pack is considered full. I've never seen a system balance at levels lower than 100%, but in theory it could be done.
Also, the SOC calculation is done by coulomb counting, but since this is prone to slight errors and will drift over time, they reset the SOC to 100% when a 100% charge is completed. This explains why capacity can be restored with an occasional full charge.
Also, the SOC calculation is done by coulomb counting, but since this is prone to slight errors and will drift over time, they reset the SOC to 100% when a 100% charge is completed. This explains why capacity can be restored with an occasional full charge.
djp
Model 3 Performance
The Roadster balances at any charge level at or above 90%. The balancing is done by bleed off only, no trickle charging. You can unplug the car and it will continue balancing.
mknox
Well-Known Member
A while back, I reported that my car would never seem to reach 100% and stop. It would be stuck at (something like) "5 minutes remaining" and would be pumping over 30 amps for many hours. I would get concerned and unplug. I was eventually convinced by forum members here to just "let it run" and so I did. My car did finally hit 100% and stop after 4 or 5 hours. I didn't gain a single mile.
mknox
Well-Known Member
My 90% fluctuates from 214-218 miles. But when I change the RM to %, sometimes it shows 91%. I think this is what some people are experiencing.
Yes that does sometimes happen but it is very rare in my experience. My old battery exhibited the behavior described by mknox where no range improvement would be noted after seldom 100% charges. And it would not "stick" at 100% for many miles as others have reported.
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