At the minimum, widespread awareness will help other future owners know that they might get a "bad" pack that degrades up to 30% without the ability to make a warranty claim, and if they're okay with that, then at least expectations are set correctly. If I know a 300-mile rated car could actually only provide 210 miles of *rated* range, I personally would not value it enough to buy it, but others might.
This is my main takeaway. It'll be the first thing I tell prospective owners. We absolutely would not have paid the $75k (Canadian) we did on the car had I known there was a 30% allowance on the early-life capacity. It's not like it's 15% one way and 15% the other - the 30% is
all negative potential. Fine if it works out (and so far it has for us, thankfully), but that's an expensive gamble. We really, really do need the range - 20% reduction would mean we now need a gas car again and the purchase would've been pointless. This will be the case more often than average around me (things are spread out here).
As for why 20% drop wouldn't be workable - effectively use 10-90%, so 80%, drop efficiency by 30%
average in Winter. That's 56% real-world range compared to rated, about 280km. This is on the very edge of our needs for the car already, and another 20% off that would not be workable without massive sacrifices and/or a gas vehicle backup.
I thought all SR+ cars moved up to 250, was it only cars sold after a certain date?
While I understand a 10% loss is frustrating, are there really many/any SR+ cars out there which have lost much more? I just look at it as the 10% is a limited time range bonus. Any owners lost 20%? Outside of the 90 pack on the S/X or really old cars, I can't say I have heard of many.
Technically all SR+ may have been moved up to 250mi max, but any that were already sufficiently degraded (i.e. pre-2020) wouldn't be able to show it anyways. Given that SR+ seems to have worse degradation on average (anecdotal, not verified) I think
most people would chew through that 4% pretty quickly, even before factoring in that they're not shipping with 250mi on the display to begin with.
It makes sense SR+ would have worse degradation than LR. They deal with more or less the same power loads (climate control is exactly the same, aerodynamics are exactly the same, weight on hills is notably different), despite having a smaller battery. Therefore the relative stress would be higher on the SR+ packs than the LR ones.
Funny enough, this is how Tesla gets away with looking
so good compared to earlier EV options. They shoved the biggest packs in that they could and declared victory. See it like this: If a trip takes 10kWh to heat the cabin throughout, how do a 20kWh battery and an 50kWh battery compare?
Half of the 10kWh went just to heating the cabin, but only 20% of the bigger pack. It's magic.
EDIT: There's a simpler explanation, upon re-reading this part. Doh. The cycle count on SR+ will also be higher than an LR pack for the same number of miles travelled. This is also why their warranty is less, and why Elon gave
two numbers for lifetime expectations of the battery (one for SR+, one for LR). SR+ absolutely has more stress than LR over its life, and
will degrade faster.
Arctic_White: Your post is likely spot on, and I certainly don't disagree with it. While I am an Electrical Engineer and deal with this sort of thing, I am by no means anywhere near being an authority on batteries, certainly not present day Li-Ion design. I've been through all the foofaraw over NiCads and all the rest, "memory", and so on.
I would, however, enjoy having a definitive source for correct information. Has Tesla ever come out and specifically stated "For best battery life and least range degradation, we say to ... " and state the procedures and numbers?
I fear there is so much anecdotal information floating around out there "happened to my Uncle Fred, he saw the see-ment in the car...", we may never know the best measure.
As I said in my post, until I get an official ruling from a truly authoritarian source, I;m just gonna let the car tell me what I need, not charge to 100% unless absolutely necessary, and enjoy the living Hell out of driving my rather nifty automobile. There are enough Superchargers, Level II chargers, and places where I can plug in my adapter, I just don't worry about it. Yes, it takes a little more thought to long distance driving in a Tesla, but it is a small price to pay, $16 for a trip that used to cost me $82, for starters...
As it happens, if I plug in when I get home from work, I am back to 90% by the time I leave the next day. That works for me. YMMV, as it were...
From my observation, people on the forums started recommending the charge/discharge/calibration after Tesla Service employees started doing so. The employees didn't recommend
exactly the same procedures (some even conflict) for every person, but the theme was the same: charge high, drive it down low, repeat.
That's as official a source as we're going to get probably. It's unfortunately the same source that told
many people that the battery gauge changes based on how you drive (which Tesla had to release a statement saying it doesn't). Personally I don't buy all these "calibration" processes. If the BMS is so poorly designed for adapting to real life charge habits (which Tesla had years of info on prior to the Model 3)... I just don't think that's real. And anecdotally, there's quite a load of people on these forums that the process didn't help at all (or in some cases ended up reporting
less capacity). I think confirmation bias with a relatively misunderstood system is to blame.
People ultimately want a reason and a fix. "Bad estimate" gives them a reason, and "charge and discharge" gives them something to try in the absence of Tesla actually caring about our (very real and accurately reported) degradation.
Tangent: What we know from other info posted here is that all these recommendations to charge high then discharge then immediately charge again bypass the only understood process of estimation from the theory of operation documents. Someone here pointed out a rest period is needed both before and after. Really, this makes a lot of sense to find the resting open-circuit voltages (along with the other info known/estimated like internal resistance and measured capacity). The rest period advice is absent from all the recommended calibration processes, even flat out discouraged in the cases that recommend charging to 100% of course.
