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Battery Charging Best Practices

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Where does it say that and why is running the battery down to 20-30% before charge a bad thing? Isn't that what you are doing when you go on a trip? You start at 90% run it down fairly low charge, rinse repeat. My question is does it matter if this takes 5-10 days to get to 30% before charging?

From the owners manual of the Models S, X and 3:
"There is no advantage to waiting until the Battery’s level is low before charging. In fact, the Battery performs best when charged regularly."
 
Where does it say that
In the manual, on page 129 (pdf page 130) in the May 16, 2019 dated manual here:
https://www.tesla.com/sites/default/files/model_3_owners_manual_north_america_en.pdf#page=130
About the Battery
Model 3 has one of the most sophisticated battery systems in the world. The most important way to preserve the Battery is to LEAVE YOUR VEHICLE PLUGGED IN when you are not using it. This is particularly important if you are not planning to drive Model 3 for several weeks. When plugged in, Model 3 wakes up when needed to automatically maintain a charge level that maximizes the lifetime of the Battery.
Note: When left idle and unplugged, your vehicle periodically uses energy from the Battery for system tests and recharging the 12V battery when necessary.
There is no advantage to waiting until the Battery’s level is low before charging. In fact, the Battery performs best when charged regularly.
This jives with the scientific research on the matter available online and in many youtube videos. Shallower depth of discharge is better for battery health. Charge 10% 7 times a week is healthier for your battery than 70% once a week.
e.g. (A) Charge 80% -> 90%, drive down to 80%, repeat x 7days/week, is better than (B) charging 20% -> 90%, drive down to 20%, repeat once a week.

And if you really only need 10%/day, storing closer to 50% is healthier as well, so a better pattern for battery health would be charging 45% -> 55%, drive down to 45%, repeat.

and why is running the battery down to 20-30% before charge a bad thing?
It's not a bad thing, but it's not the best thing.

Isn't that what you are doing when you go on a trip? You start at 90% run it down fairly low charge, rinse repeat. My question is does it matter if this takes 5-10 days to get to 30% before charging?

A trip is a more infrequent use case, and you can't very well charge 10-20% every few minutes driven :)
It doesn't matter how many days it takes you to get to 30%, what matters is if you can avoid using such a deep amount of discharge and equally deep amount of recharge. If you are on a trip, 90->30->90 is fine. If you are weekly commuting 60% total, with only 10% a day, it's better to charge daily to avoid deeper discharge amounts.

I am mainly thinking about the health of the 12V battery, not main battery. In an ICE car the 12v battery gets topped off by the alternator when you drive. If you let an ICE car sit for 2 weeks you may not have enough juice to start the car. In the Tesla I am interested in understanding how the 12V battery is managed and charged. Does it only receive a charge when plugged in? Does the main battery charge the 12V battery automatically and if so does it wake itself up from sleep if the 12V battery is losing too much voltage. I know some are going to say just plug it in and don't worry about it but inquiring OCD folks like me want to know. :)

The answer is underlined. It charges it whenever, including when it's asleep and wakes itself up to do so. You can't drain the 12V battery, even if you leave a powered 12V accessory plugged into the 12V outlet, it says so in the manual now as well.
 
Ah. Then you need to be looking at threads about how the 12V battery is managed, not about charging practices for the car.

What charges the 12v battery and when?

Any reason not to hook up a battery tender to the 12 volt battery ?

When does 12V battery actually get charged

Thanks for the links.

Yes, thanks. Also here's another one with some more recent posts triggered by someone's questions about using a 12V-powered cooler.

How and when does the 12v battery get charged?

When searching for quotes above in the manual about leaving the car plugged in I realized there is new wording describing when the USB and 12V accessory outlet remains powered. I posted that info into the more recent thread I just shared the link to above.
 
I see people are yet again mixing up Tesla's sales-oriented recommendation with the scientific what is actually best for the battery. (@TexasEV ) The thing of keeping it at 90% all the time and keeping it plugged in all the time is for customer satisfaction of always having enough range, at the cost of a small penalty of it being a little bit worse for the battery's lifetime.

Tesla does not want to have to get into these kinds of long explanations and "it depends..." kinds of things with millions of customers, so they want to have one simple answer they can have their sales people give that is a pretty good answer that works fairly well for all circumstances. It's not the best for each person's scenario, but it's good enough.

Physics is physics, so I am sure that, with the physics of how batteries work, means that there might be slightly more degradation doing that, than actively trying to charge to 80%, only plugging it in when needed, all of the "it depends" stuff.

But..

(making up numbers here, emphasis on made up numbers)

If actively managing the battery, performing a bunch of mental gymnastics to try to "optimize" the batter means the battery half-life is 30 years, and "just plugging it in" means the battery half life is 28 years, that means actively managing the battery would be "better", but irrelevant, because its unlikely anyone has the car either 30 or 28 years.

Thus, it could be "better" but "not matter" and I suspect (but have no proof) that is what is happening here. In my completely made up numbers above (for illustrative purposes only), 2 years is a statistically relevant size, but at the same time not relevant to 99% of most owners of the car.

So, if the above is something like what is going on (with different numbers of years for half life of battery), its easier and better for tesla to tell people to "just plug it in" because it "doesnt matter".

I have zero idea what the numbers are but suspect that something like the above is whats going on. I only know for my own car, I have 8500 ish miles now, drive about 80 ish miles a day round trip to work, and plug in every night with a HPWC at 48amps in my garage. I charge to 90% every night, my car reported 90% at 279 miles when I picked it up and it had 12 miles. It still reports 279 miles on 90% charge with 8500 miles.

The first month I was stressed out about "doing it right" just like most new EV drivers are (this is my first EV, unlike some others I did not move from a leaf or bolt or some other ev, I jumped in here). I went from stressed about it in the first month to 6 weeks, to just happily plugging it in when I get home and "not thinking about it" at all (except for enjoying the fact that I never have to plan to go to a gas station to fill up after work, or before I go to work).

I used to "fill up" every 4 ish days or so, for just under $50 per fill up of premium gas for my BMW 435. I had to drive that car in sport mode all the time to get the performance I wanted out of it, and I am not "boy racer". A BMW in "comfort" mode is really almost like a camry, and if you paid for a car with performance you kind of want a performance car.

My tesla gives me ALL the performance, with none of the drama or noise, and is much cheaper to operate. I am no longer stressed about the battery, or "doing it wrong" I just plug it in, and get bemused by the constant threads about "how do I do this right?"
 
During bad weather, I suggest charging battery to 90% and leaving car attached to power.

You don’t know when power could be interrupted, delay until restored or whether you would choose to /be required to evacuate.

I also suspect there’s benefit in discharge to relatively low level, then back to a high level. When BMS can balance modules it learns which may have bad cells and how to distribute demand accordingly.

Finally, when I charge to 100% for a trip after several months of 90% and lower, the car spends as much as an hour more than estimated getting from 97% to 100%. Expect that time is balancing charge level across modules.
 
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Professor Jeff Dahn likely knows more about Tesla's battery chemistry than any other person: his recommendation is 70% to optimize battery life. Elon has publicly said 80%. The manual suggests 90% (however, this is more likely to be a marketing driven answer than a purely technical driven answer). As others have said, we are likely splitting hairs about the overall difference in battery life, but since I don't really need more than 80% for my usage (unless taking a trip), I leave mine at 70 or 80%. And leave it plugged in.

Tesla battery expert recommends daily charging limit to optimize durability - Electrek
Tesla Battery Expert's Recommendation For Maximum Battery Life - Video
 
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Just got my SR+ and after a full charge it says 344klms. The website said 387klms. Why this difference?

PS. I charged it from a regular house outlet. Is there a chance it does not charge to 100%?

Look at the charging page on the car or in your app. The car is likely set to 90% as maximum charge. If that is the case, the numbers you are seeing make perfect sense.
 
If actively managing the battery, performing a bunch of mental gymnastics to try to "optimize" the batter means the battery half-life is 30 years, and "just plugging it in" means the battery half life is 28 years, that means actively managing the battery would be "better", but irrelevant, because its unlikely anyone has the car either 30 or 28 years.
That is a very handsome looking straw man. Using a limit lower than 90% takes no "mental gymnastics".
 
Pretty much all companies, Apple..., whose products involve Li-ion batteries avoid telling you best practices, presumably because they want their consumers experience to be pleasant and worry free.

Interestingly, Apple is introducing a feature in iOS 13 to address this. For overnight charging, battery will charge to 80 or 90% (forget which) right away and hold the SoC. The phone will resume charging and reach 100% SoC at your learned wake-up time. I've been semi-religious about not charging my phone battery overnight and just topping up in the morning on the way to work. This will save me from that headache and make my phone experience more pleasant and worry-free.

I hope Tesla will eventually implement a similar feature. No doubt they could do it and it's probably already on their feature backlog, just super de-prioritized. Ready for release on Version 2033.31.4!
 
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Summarizing what everyone has posted so far my understanding is:

1) Tesla does not publish detailed best practice information beyond the limited comments in the owner’s manual
2) The strategies people are discussing are either anecdotal or based on charging of lithium ion batteries in general but not specific to Tesla vehicles
3) The difference between charging to 70%, 80% or 90% is possibly statistically significant but likely not meaningful enough to worry about
4) It is generally agreed that charging to 100% on a regular basis is not a good idea.
 
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Summarizing what everyone has posted so far my understanding is:

1) Tesla does not publish detailed best practice information beyond the limited comments in the owner’s manual
2) The strategies people are discussing are either anecdotal or based on charging of lithium ion batteries in general but not specific to Tesla vehicles
3) The difference between charging to 70%, 80% or 90% is possibly statistically significant but likely not meaningful enough to worry about
4) It is generally agreed that charging to 100% on a regular basis is not a good idea.
:) Yes, that is a very good summary. I will add a little detail into number (3). Every step is not the same amount of difference. The impact is on a bit of an exponential scale, depending on how far it is from an extreme end. In other words, if you take a 10% difference:
Using only 90% as your limit instead of 100% does really noticeable huge benefits to the battery.
But you've already gotten the bulk of the advantage, so using 80% instead of 90% is a far less impactful change. And 70% instead of 80%, even less noticeable results.

This is one of the main things about why it is such a game changer for the electric car industry moving toward bigger batteries. When there were dozens of models from every car manufacturer making these short range electric cars that all had 80 miles of total range, they usually needed to stay charged at 100% almost all the time just to be practically useful. That was awful for the batteries and was destroying them in short order. It created rapid degradation across the board and continued the bad reputation and negative "common knowledge" among the public about how terrible electric cars were. We're here debating about various levels, but just having a car that has enough range to even be able to use 90% or less is a massive improvement.
 
short range electric cars that all had 80 miles of total range, they usually needed to stay charged at 100% almost all the time just to be practically useful. That was awful for the batteries and was destroying them in short order. It created rapid degradation across the board and continued the bad reputation and negative "common knowledge" among the public about how terrible electric cars were. We're here debating about various levels, but just having a car that has enough range to even be able to use 90% or less is a massive improvement.
Brilliant!
 
1) Tesla does not publish detailed best practice information beyond the limited comments in the owner’s manual
2) The strategies people are discussing are either anecdotal or based on charging of lithium ion batteries in general but not specific to Tesla vehicles
3) The difference between charging to 70%, 80% or 90% is possibly statistically significant but likely not meaningful enough to worry about
4) It is generally agreed that charging to 100% on a regular basis is not a good idea.
--Reasonable summary. I would add one more thing. Temperature matters. In hot weather the benefit of 80% vs 90% in enhanced. In hot weather charging above 80% when you don't have a reason to is possibly inadvisable.
 
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