Prolong battery life strategies

[seattlerock]

So confirmed my order for a s85 yesterday and wondering about the best charging strategies.

For example is it better to slowly charge the battery by setting the amp rate lower than the outlet is capable of?

Also considering not charging every night. In general my roundtrip is around 20 miles a day, should I only charge on Fridays for the weekend?

 

[David99]

From all I learned about Lithium batteries there are a few major things. Most important is state of charge. The higher the battery is charged, the faster it ages. So avoid keeping it charged 100% for a long time. The best way to do it is use the charge level slider and the charge timer. Only charge as much as you need plus a reasonable buffer. Set the timer so the charging starts later and is just finished in the morning, when you leave. This way you keep the state of charge low for the most time.

Driving the battery down very low is also bad for it. Basically avoid both extreme ends. 100% and 0%. The car won't allow you to go to either end actually as it's the worst thing for the battery.

Lithium batteries have their highest capacity and performance when they are warm. I think around 40-50 degree Celsius. The chemical reactions happen easier in these temperatures. Unfortunately the chemical reactions that cause battery aging also love these temperatures. So while the battery performs well when it is warm, for long term battery life, cold temperatures are better. Elon said at some point that in Alaska the battery will last 'forever'. Low temperatures slow down the chemical reactions in the battery, the good ones and the bad ones.

The charge and discharge rate doesn't seem to have as much of a bad effect on the battery. In typical driving and charging the load on the battery is pretty reasonable. Even supercharging is not crazy actually. It is only 1.4 C at the beginning and then is reduced the more the battery is charged. Elon said in a Q&A that the Superchargers are actually conservative. The batteries can handle much higher rates but they don't have enough long term experience with it yet so they are staying on the safe side. So don't worry about using Superchargers. There is a test going on where two Nissan Leaf are running parallel. One is charged normal, while the other one is quick-charged all the time. The difference in battery degradation is very small and the Leaf doesn't even cool the batteries down while quick charging, which the Model S does.

BTW Tesla specifically recommends to have the car plugged in all the time. That doesn't mean you should keep it charged full or high all the time. That's why the charge slider is adjustable to anything between 50% and 100%.

 

[Bardlebee]

To note about the charge level, the manual literally states:

2.
Adjust the charge limit based on your
anticipated driving needs. Touch Set
Charge Limit, then drag the slider bar to
the desired charge level. You can charge
to any level from 50% to 100%. For daily
driving, charge between 50% and 90% to
improve battery longevity. Charge above
90% for trips requiring maximum range.
The setting you choose applies to both
immediate and scheduled charging
sessions

So I imagine that having it charged to 90 percent should be fine too, that's what I am going to stick with and we will see what happens. Though David99 likely has more knowledge on the subject as I have not studied up on batteries. As long as Tesla tells me its okay, I will do 90 percent as I am not going to try and assume Tesla's tech.

EDIT: My round trip is the same as yours, I plug in the vehicle when I get home every day without fail. Simply for the batteries sake.

 

[Caloncho]

So confirmed my order for a s85 yesterday and wondering about the best charging strategies.

For example is it better to slowly charge the battery by setting the amp rate lower than the outlet is capable of?

Also considering not charging every night. In general my roundtrip is around 20 miles a day, should I only charge on Fridays for the weekend?

@SeattleRock congratulations on your order!
I was told during delivery to try and keep it over 20% and under 90%.
in real life my battery stays between 50% and 80% most of the time.

 

[yobigd20]

its not bad if you need to go to 0% or 100%. that's only bad for the battery if you go from 100 % to 0% to 100 % etc on a daily basis. that's a full cycle. two half cycles are better than one full cycle. aka 75% to 25% to 75% to 25% to 75%. Four quarter cycles are better than two half cycles. and so on. theoretically the battery could last forever under ideal circumstances (I guess something like 51% to 49%, lol). but that's not practical. there's really a few basic "guidelines" to stick to. And I say "guidelines" as opposed to "rules" because it's not bad when you need to break away from your daily charging pattern for a long trip or something.

1) as previously stated by others above, try to keep above 20% and below 80-90%.
2) charge as frequently as possible. even little errands you run. plug back in each time you get home. (keeping the charge cycles as shallow as possible)
3) try to keep the "average" charge around 50%. by this I mean if you only need to use 60% of your battery on a daily basis, then keep your charging pattern to 80% to 20%. if you only need to use 20% on a daily basis, then charge to 60% (arriving at work at 50%), drive home and arrive home at 40% and then charge back up to 60%. aka keeping that average at 50%.


if you need to charge to 100%, go ahead and don't worry about it. if you need to go all the way down to 0-5%, again go ahead and don't worry about it. just don't make that part of your daily driving pattern. probably the worst thing you could intentionally do to your battery is charge it to 100% and leave it baking in the sun. if you need to go to 100%, just time your charge such that it completes right at the time you are leaving so that it only stays at 100% for a few minutes. really that's the best we can do. I have 50k miles on my MS showing 257 at 100% charge using this charge cycle pattern.

 

[seattlerock]

Thanks for all the great tips. Fantastic community here.

 

[David99]

Great explanation from yobigd20 as well! Yes, don't be afraid to use the full range if you need it.

Just one more thing. According to studies done with all kids of Lithium batteries, charging to 90% vs 100% will have a big negative impact on battery life. Charging to 80% vs 90% still makes a difference, but not as much. Charging to 70% vs 80% makes even less of a difference relatively speaking. IOW, really avoid the extreme ends, but other than that, don't worry.

 

[AmpedRealtor]

 

[romp]

Welcome to the board!

Lots of great advices above, really nothing to add, just one point: somewhere else on these pages there was the link to this lecture: Why do Li-ion Batteries die ? and how to improve the situation? - YouTube. The science described in this flick is in agreement with Tesla's recommendations to charge it every night and don't "range charge" unless needed.

The biggest factor in battery degradation is amount of time the battery spends fully charged at high temperatures. So, my rule of thumb is: avoid keeping it fully charged in hot environment for long periods of time. Not really an issue in Seattle, though.

 

[Bardlebee]

So I've had my car a week, is it really bad to keep the car at 90 percent? You know the amount that Tesla hands the car to you? If so, why doesn't Tesla hand the car to you with 80 percent or 75 percent? I feel like there is something that could be different with the Tesla that keeps the car being charged at 90 percent to be okay.... But obviously I don't know better.

 

[djp]

So I've had my car a week, is it really bad to keep the car at 90 percent?

It's not really bad, but there's a trade off between range and battery life. If you want the battery to last forever you should keep it at 20% SOC in a refrigerated warehouse and never drive the car! Lower SOC is better for battery life, but at the same time you want to have enough range to cover your daily driving needs. Tesla recommends anywhere from 50% to 90% as a daily charge level.

 

[Bardlebee]

It's not really bad, but there's a trade off between range and battery life. If you want the battery to last forever you should keep it at 20% SOC in a refrigerated warehouse and never drive the car! Lower SOC is better for battery life, but at the same time you want to have enough range to cover your daily driving needs. Tesla recommends anywhere from 50% to 90% as a daily charge level.

Hmmm, I wonder if Tesla would add some sort of language to its manual if it would be beneficial to be at 60 percent as opposed to 90 percent. I guess it just makes you wonder if maybe they have over come this, obviously we won't know for some years I guess.

 

[djp]

Hmmm, I wonder if Tesla would add some sort of language to its manual if it would be beneficial to be at 60 percent as opposed to 90 percent. I guess it just makes you wonder if maybe they have over come this, obviously we won't know for some years I guess.

The language is already there in choosing a charge limit between 50% and 90% that fits your daily needs and avoiding full charges except when necessary. Some people misinterpret this to think that 90% is perfectly fine while 100% will immediately kill your battery. In fact it's more of a sliding scale - 70% is better than 80% and 80% is better than 90% - is just a question of degree.

 

[Rockster]

I believe that Tesla's charging recommendations are what they perceive as the best balance between battery longevity and minimizing the risk of owners (especially new owners) being stranded with a depleted battery.

The latter is especially important for a young-ish company wanting to avoid the very negative press and customer dissatisfaction that would accompany a pattern of stranded Model S's.

 

[Matias]

There is not one precise limit, which is good and which is bad. The lower the better (not bricking of course). Just one thing: Tesla's 100% charge is not necessarily real battery's 100% charge, but somewhat lower.