ghostbusta
Member
Yeah, to 80% every night. First few days I got 248 miles, then 247, and now 246 miles at 80%
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Model 3 Performance Battery Degradation One Month (Story)
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Here goes.
As I understand it currently, the displayed range is in fact what is called "Rated Range" which is a calculation of range used by the car that looks at current battery capacity and divides that by a static EPA-derived wh/mi (which folks seem to think is around 242 wh/mi). So, a fully healthy battery at 75kw = 75,000 watts, so 75,000 / 242 = 310, just about.
And so it would seem to me that the Rated Range equation apparently looks like this for L/R Model 3's:
75,000 w
------------ = Rated Range (310 - actually 309.9 but rounded up)
242 wh/mi
With the denominator of 242 wh/mi being a constant, nothing can change this number in the equation - Tesla ignores actual wh/mi used in calculating this Rated Range number that is displayed. This means it matters not one whit how you drive the car, how much AC you're blasting, etc. Even if you're at 350wh/mi ave consumption, the Rated Range calculation still uses 242 wh/mi as the denominator, always always always.
But . . . . the numerator, the capacity, the 75,000w, now that *can* change. In these ways:
(1) Temperature: Temperature can affect the displayed rated range number because colder temps change the numerator of the equation, the 75kwh number. When it's cold (like really cold, not like "oooh it's 65 degrees" cold) the capacity of the battery can decrease. Affecting capacity of the battery means when the car looks at (or measures) the capacity of the battery, in cold temps that numerator is less than 75,000. So now it's using a lower total capacity number to use against the still-static EPA 242 wh/mi denominator number. Result is a lower displayed rated range.
(2) Actual Degradation of the battery Pack: If the pack's actual capacity literally does degrade, then again that numerator number of 75,000 w goes down, and rated range goes down as a result. The question then becomes - is that degradation at a normal or abnormal rate/amount, for the current life of the battery.
(3) Out-Of-Balance Battery Pack: Folks say, a lot on the forums, that battery packs for these cars can come "out of balance". Not sure exactly what that means, or how that works, but the recommendation is to "re-balance" your pack by depleting down to 10% SOC and then charging up to 100% SOC. That might result in the capacity number going up, apparently. It did, for mine, a little, but within a week, that was gone, and I'm down to 288 miles rated range, lower than ever.
(4) Bad Pack: A bad battery pack! If you're losing too many cells, or if otherwise the pack is losing capacity unsusaully for whatever reason, I'd call that a "bad pack"! Bad pack; please may I have a new one . . . .
Anyway. This represents a summary of what I've come to learn on the various forums. Feel free to find fault with it, and let me know same. I'm here to learn/understand; not here to defend a position or opinion that doesn't make sense . . . . .
Something like that.
PS - I'll post something more about this after I have my car looked at by the Dublin SC late next week. Maybe the Tesla technicians will set me straight if I need that, or confirm some/all of my current understanding.
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246 at 80% still is 307.5 extrapolated full range. That ain't bad . . . . I dream of that kinda range, lately. I get around 230 displayed range at 80% . . . .
I’m not sure, last weekend was the last time I did a full charge. I haven’t really looked at the 80 or 90% numbers. I did hundreds of full charges on my Model S and only lost 5 miles of rated range after 90,000 miles and 4 years. I’ll do another 100% charge on Friday night and Saturday night as I have a couple of trips planned : )
Dr. J
Active Member
Question: Does an out of balance battery pack have less actual capacity, or less measured capacity? It makes a difference. If it's just a measurement anomaly, I don't care so much. If it actually holds less juice, I care a lot.
I think both, if some cells get too low the pack has to be shut down prematurely so it doesn’t over discharge that cell. That’s why you want all cells brought up to full capacity at some point. The ones that keep discharging the fastest will be your weakest link until you get it balanced with the rest of the pack.
Some random comments
1.Charging every day if not necessary shouldn't happen. If you battery has tomorrow distance+50 miles don't charge.
Charging cycles are mild in home installation but still are charging cycles.
2.request to discharge to 10 miles and charge back to 100% comes from experience with old types batteries, I can not believe to see such advice from Tesla representative. You don't need it, in fact full charge cycles better be avoided for Tesla's size batteries. They really have to state it as clear as possible. Charging ones per month 100% means to do re-balancing. You actually need it only after big "events", i.e. long time riding and serious thermoloads.
3. I still have to see BMS which doesn't hang to programmed charge level as some religious zealot. So indeed keeping your auto plugged if not necessary is not useful.
What is the best charge to keep you auto with. Nominal for storage is 30-45%(depends on composition) but of course nobody wants to keep his auto that empty. Realistic is 30-80%. Stick to these numbers.
It is paramount for Tesla to produce simple educational video clips about batteries, charging, using and fire protection.
Not sure how to reconcile this with the advice in the owner’s manual to “leave your vehicle plugged in when you are not using it”?
Ask Tesla representative why it's in the manual.
I suspect it is a relics of the first Model S and V12 problems they had in the beginning.
It's usual case of overprotecting "guidance" which simplifies company's service while actually costing you your battery life.
It's not that serious for Tesla's (besides may be V12 in some circumstances), but for laptops normal practice of keeping your battery in while plugged costs you 50+% of battery lifetime. Instead of 8y standard (and 10y real) you get 3y warranty at best and more often than not 2y real lifespan.
No that’s not “still a charging cycle”. Plugging in when you get home at 80% and charging up to 90% for example is only 1/10 of a charging cycle. You don’t save charging cycles by charging less often, the energy you use has to be replaced one way or another. Smaller, more frequent charges are better for the battery according to the written instructions from Tesla. (No, I don’t trust what some random service or factory employee says, but I do believe it when it’s written in the owners manual). If you think you know more about Tesla’s battery and battery management system than Tesla’s battery engineers, go ahead and do what you think is best. I’ll follow what is in the owners manual until Tesla changes it, and I would encourage new owners to do the same.
Eno Deb
Active Member
It's almost certainly not balancing, but simply charging very slowly to carefully top off the battery.
Eno Deb
Active Member
Laptop batteries suffer when always plugged in because they are constantly charged 100% and exposed to more heat. None of this applies to a Tesla with a lower charge limit and active battery cooling.
Heat indeed is not an issue (beside longer supercharger sessions), constant recharging to keep your target charge level still is. And even if it is less than 4.2V, it is still cycling.
Battery "training" of LiOn is still a way to shorten it's life.
Counting life in charging cycles is simplification, and was derived during Lead-Acid Battery epoch and their applications in airplanes industry.
as I wrote already the only real enemy of LiOn are time and temperature. Obviously shorter charges are better for LiOn, primarily because of temperature, but going from 80% to 90% is not 1/10 of a cycle. the dependence is not linear and does depend very much on existing levels but it is always more.
I don't know how it is in Tesla, may be Musk found his way there too, but elsewhere the manuals are always trade off between technical description, serviceability, usability and liability.
last two always win. You see less and less details in modern manuals. Just wait and see that what I wrote will become "triviality" over two years.
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Balderdash. Well established that 5 year old model S like mine has ~5% loss... been plugged in every night.
My 4 year old model S only lost a couple % (5-10 miles) after 90k miles and 100% charges every weekend. It was plugged in every night to 90%.
I’m going to do same thing with my model P3D -. 100% charge every weekend as I usually do trips. So far after 2,300 miles it has only lost 2 miles range. Pretty much same as my model S did.
I’m going to do same thing with my model P3D -. 100% charge every weekend as I usually do trips. So far after 2,300 miles it has only lost 2 miles range. Pretty much same as my model S did.
Here's what's ambiguous about that direction to me: Leaving your vehicle "plugged in" does not necessarily mean it's charging, does it? You can plug in the charger but not set the car to charge, right? Or, if you set the charge level low (to 50%, e.g.), and the car's at 80%, then you would have the car plugged in, but not charging (until it got down to under 50%). It would be just a touch clearer to me if the manual talked about healthy SOC levels, and whether you should charge every night to those levels.
After following the advice of the tech I spoke to as referenced up thread, my extrapolated range has now returned to 310 miles so I must conclude he gave me good advice. I have not done another 10-100% charge yet since it hasn't been a month but did start only charging when my range gets below 100 miles back up to 70% which again shows between 212-217 so I'm pretty happy. Taking it off the timed charge when I do charge means I usually have to go out and plug in the car to take advantage of the TOU rate but I don't mind doing that. I'm going to try plugging it in, stop the charge and leave it plugged in so the car can use shore power to preheat etc. as needed and I can start the charge via the app without going out to the car in the cold. Really happy with the results so far and I know I will get flack about "but the manual says" blah blah blah. Do what works for you and your own charging habits.
The only reason to set your charge limit that low is for long term storage. Why wouldn't you routinely charge to 80 or 90%? Don't tell me it's to save the battery. The battery will be just fine at normal charge levels. Tens of thousands of Model S owners have the experience of losing only about 5% range at 5 years when charging daily to 80-90%. You're not going to do meaningfully better than that with a lower charge level.
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