But that was not the issue you were bringing up. You complained of the amount of energy changing very quickly when left to sit and settle. And that is exactly what it does when it is in that part of the line with the voltage change being very steep.
You are confusing the voltage with state of charge. The two are very different things which is why it is difficult to determine state of charge from the voltage. Instead they measure the current and integrate that to measure the amount of charge remaining in the battery. To get energy they factor in the voltage curve, but the details of the curve shape does not cause the effect you are describing. 5% is 5%.
Well, not really. As some people have pointed out, Tesla seems to have re-instituted the "below 0 buffer", where the car will usually have a bit left when the meter gets to displaying 0%.
By "wee bit" you mean nothing you can count on? Yes. There is no hard limit to the power you can extract from a battery until the current and voltage drop literally to zero. The cells would be destroyed by that so they pick a point where the damage is minimal as they do at the top end. So the "zero" point is soft and they can play games with it.
I just reread it, in context, and yes, it absolutely makes perfect sense. This is what you said:
When you are driving the car, it obviously can't be plugged in.
Ok, now you are being absurd.
Sitting in a parking lot, it will frequently not be plugged in.
That isn't the issue. The issue is what Tesla says to do which is to keep it plugged in any time it's not driven.
The cars can sit for several days at a time without being plugged in, and they do not suffer harm from that either. "at all times" is definitely an exaggeration and not really what Tesla recommends exactly.
See, that's wrong. If the temps are well below zero, the battery needs to be plugged in so it can heat itself. In "several days" it would be depleted and damaged. THAT is what this is about.
But I was explaining why Tesla would give a recommendation similar to that about keeping the car plugged in excessively more than it needs. And having to fight that wives' tale misinformation about remaining plugged in leading to overcharging and exploding is one of the reasons they needed to say that, which was not related to idle drain energy consumption. So you brought it up, and I explained multiple reasons of why they published that type of recommendation. That was just one of them.
Yes they do!
I've given you examples of how the information is inadequate. I'm not going to rehash word salad with you.
As much as is really needed. It's the simplest way to get the best balance of most benefit for the most amount of people for the most use cases.
However, they are selling a consumer product. If they were to give excessive detail with many pages of steps and charts of various conditions and how to do things several ways to be the most perfect, it would have two negative consequences:
They already give excessive detail. People are used to ICE vehicles where you just have to keep enough antifreeze in it to keep it from freezing and you might need a block heater for winter starting. That's pretty durn simple. Tesla battery care is much, much more complex with cautions about charging, discharging, too hot, too cold...
1. It would be problematic for some people's use cases, where they need to use their cars outside of what is the most "ideal" treatment of the battery. And then that would mount up to lots of calls and service visits with people trying to reconcile that contradiction between needing a car they can use but being concerned with violating these recommendations and conditions.
2. It would feed the FUD of the haters and the fears of those who just don't know but are scared and worried about new technology they don't understand that well. If it has complicated steps and conditions they have to remember, that will seem overwhelming and discourage them from considering buying an electric car. And they would continue spreading these negative rumors about how electric cars are too scary and complicated to use.
So for those reasons, Tesla doesn't want to go too over-the-top with making it complicated. They keep it pretty simple, with the 50% to 90% being OK for constant daily use, and above 90% being OK for occasional use. Simple. Don't worry people. If you park with a very low state of charge, it will display a simple message saying you should probably plug in. If you charge it up really full several times, it will also display a simple message saying it's not a good idea to do that a lot. Also simple.
They need to tell you specifics of how much damage charging to 90% does, charging to 95% and charging to 100%. My cell phone tells me that. Seems simple enough to me.
No. That is not required. If people never look any of that up or do that research, THEY WILL STILL BE FINE. It is not required to obsess like that.
Obsess??? The battery in my car is as much as many people's cars! Yeah, I want to optimize the wear on it since it is the most expensive and most subject to wear and isn't really warrantied. Yeah, I want to take care of it, but I need to use it too!
As I just mentioned above, people don't need to look this up or worry about it. The car will give a simple message guiding you.
It does??? What something generic that you shouldn't charge beyond 90% "too much"? I don't recall seeing that because if it does, I would pretty much dismiss that as containing virtually no information. How much is "too much"???
It's fine. And really, this kind of seems like you're not being serious here. Plenty of things in life are known to be bad to do excessively or constantly--eating junk food, excessive alcohol, smoking, revving your car to redline, speeding. People moderate things all the time in their lives without having to know an exact quantified number of what the impact will be of doing it too much. "This generally isn't good; I shouldn't do it all the time."
Ok, so how often is ok? 50% of the time? 20% of the time? 10%, 5%? I often read that supercharging damages the batteries yet there is NO mention of that in anything from Tesla that I've seen. Are people making that up? Or is Tesla just not warning us about it for their own reasons?
I think you are being rather disingenuous about this.
I am sorry that you have so much anxiety about this, and I am trying my best to let you know that you DON'T need to obsess and worry about this so much. They designed these with extremely detailed systems to prevent people from being able to accidentally destroy them. It's the public--they know what the public is like. I wouldn't recommend what you are suggesting, of parking the car in the cold with a very low state of charge and then leaving it that way for a week. It's not that it's going to destroy the main battery, but just because you will probably cause yourself a lot of inconvenience.
You characterize my concern as "anxiety" because you've never bothered to actually consider the issues and so don't know enough to know what to be concerned about and what is actually ok.
So what is a "very low state of charge"??? 10%, 20%, 40%??? I don't have information to know what will work and what won't.
If the car is really running low and can't get recharged, it will just keep the main pack disconnected, with a safety buffer of energy left in there (that you are never allowed to access) so that the battery will not be drained completely and harmed too much. The idle systems in the car will eventually drain the little 12V battery, so you will have to get service or a tow truck or something to deal with that hassle and maybe have to replace that 12V, but you can get it somewhere and get it charging, and it will be OK.
So you don't know any more about this than anyone else? Ok, thanks for the entertainment.