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What should my ideal charge percentage be?

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Elon's referring to regen being disabled or reduced when charging above 95%. There's no difference in regen at lower charge levels.
That's what I read as well.

A quick caveat though: If you're charging at the top of a mountain, a 90% charge might become a 95% charge rather quickly as you make you way off the mountain. So capping out at 70% (or less) might be a good idea if you value "regen behaving consistently" on the way down.
 
People asked for this feature so Tesla provided it. Now people say it is too complex.

Um, different people, most likely. ;-)

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The US Army study is on the Roadster chemistry (LiCoO2) and the NREL study is on the Model S chemistry (NCA). Both studies have similar results, and Tesla battery management is similar for both the Roadster and Model S, so the general principles can be applied to both.

(...etc.)

Great, thanks, djp!

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Not that this will sway anyone who's really into this thread, but...

Ah, Elon. :frown: His 85-90% for "best life" contradicts (a) Tesla's own "charge what you need" directive and (b) the studies referenced in this thread. I'm guessing I should take Elon's tweets with a grain of salt . . . ? :confused:
 
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Which mountain would that be? Charging infrastructure is coming along faster than I realized....:wink:
How about the mountain I live on? I live at 6130' elevation, where I charge my LEAF, and regularly drive down to 1200' and back up. Regen is ideal if I only charge to 40-50% before the long descent (14 miles) but isn't too bad at 65-70% as long as the battery isn't cold. Owning a Tesla, when that time comes, sure will make for a nicer drive!

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Ah, Elon. :frown: His 85-90% for "best life" contradicts (a) Tesla's own "charge what you need" directive and (b) the studies referenced in this thread. I'm guessing I should take Elon's tweets with a grain of salt . . . ? :confused:

"85-90%" probably makes for better PR than very publicly advising people to use only half of the battery!
 
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Ah, Elon. :frown: His 85-90% for "best life" contradicts (a) Tesla's own "charge what you need" directive and (b) the studies referenced in this thread. I'm guessing I should take Elon's tweets with a grain of salt . . . ? :confused:

I read Elon's tweet in the context of a Standard charge vs a Range charge. 85-90% is best for battery life compared to charging over 95% and also gives you full regen instead of partial regen. In that case there's no contradiction with the charging screen and the regen comment makes more sense. It's tough to get into details with an eleven word answer.

It's also interesting that they're guiding down the charge level for a "Standard" charge. The old Standard charge was 93% and the new equivalent to a Standard charge is recommended as 85-90% which sacrifices some range for better battery life than the old Standard.
 
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I read Elon's tweet in the context of a Standard charge vs a Range charge. 85-90% is best for battery life compared to charging over 95% and also gives you full regen instead of partial regen. In that case there's no contradiction with the charging screen and the regen comment makes more sense. It's tough to get into details with an eleven word answer.

Okay...not how I read it. But yeah, tweets are kinda useless for imparting actual information.
 
Elon confirmed on the Supercharger conference call that average SOC is the most important factor for battery life, with Supercharger use having little impact. He saidkeeping the battery at mid charge and cool will extend the life of the battery.
He did not say either underlined portions. "Average" implies something different than he said. "Extend" means something different to me than what he said.

Here's my transcript of what he said:
What's more important in SOC; not storing the pack when full. Cell phones and laptops are typically kept in the worst conditions. Best thing is mid SOC and cold.

Note that "in" should be "is". That was a typo. Mea culpa.
 
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Agreed it's a matter of interpretation and I haven't listened to the replay yet. My point is the comment "Best thing is mid SOC and cold" is consistent with the battery studies and with Tesla's own advice to charge to what you need.
 
He did not say either underlined portions. "Average" implies something different than he said. "Extend" means something different to me than what he said.

Here's my transcript of what he said:


Note that "in" should be "is". That was a typo. Mea culpa.
Here's what I think is meant by mid-SOC. There is probably some "perfect" midpoint with a slight drop off as you move away from it. This drop off starts to accelerate rapidly as you cross past 90% / 10% resulting in a curve that looks like this:

Battery Life.jpg


I wouldn't get too hung up on the exact numbers I used, or even the midpoint -- I picked them to illustrate that the mid-SOC is actually a wide range and most users need to keep their SOC out of the extreme high and low areas of the curve for extended periods.
 
What kind or range numbers are people seeing?

I set my charge point to what looks like 80%. I got 198 rated. That would only correspond to 253 full charge. At some point, I'll do a range charge and see what I get - but does any one else have any 4.5 numbers?
 
Picked my Blue 85 up two days ago in Raleigh. Just an amazing car. I live in a small community only 2 miles from my part time job so most days my total miles are 10-15 depending on errands around town. Every other weekend we drive to Charlotte 125 miles each way. Other than the night before the Charlotte trip I plan to charge at around 65%. Two questions: Since I normally need so little of a recharge each day is there any advantage to a slower charge at 110 versus my NEMA 14-50? Secondly, I know the recommendation is to plug in every day/night but again since I normally need so little recharge is there any harm in only plugging in every second or third night?
 
Picked my Blue 85 up two days ago in Raleigh. Just an amazing car. I live in a small community only 2 miles from my part time job so most days my total miles are 10-15 depending on errands around town. Every other weekend we drive to Charlotte 125 miles each way. Other than the night before the Charlotte trip I plan to charge at around 65%. Two questions: Since I normally need so little of a recharge each day is there any advantage to a slower charge at 110 versus my NEMA 14-50? Secondly, I know the recommendation is to plug in every day/night but again since I normally need so little recharge is there any harm in only plugging in every second or third night?

It may be less efficient (use more energy) to charge at 110V. I'd probably just charge at 40A and still plug in every night. Just set your charger to start an hour or two before you wake up each morning. There isn't any harm in charging every other night but not any benefit really either. With the car lacking sleep mode right now better to keep it plugged in each night and you get in the habit of doing so.
 
Here's what I think is meant by mid-SOC. There is probably some "perfect" midpoint with a slight drop off as you move away from it. This drop off starts to accelerate rapidly as you cross past 90% / 10% resulting in a curve that looks like this:

View attachment 22910

I wouldn't get too hung up on the exact numbers I used, or even the midpoint -- I picked them to illustrate that the mid-SOC is actually a wide range and most users need to keep their SOC out of the extreme high and low areas of the curve for extended periods.

Here are the actual degradation rates from the NREL study:

NREL Degradation Rates.png


There are diminishing returns in battery life from dropping SOC with the biggest step being 100% to 80%, but even at low SOC levels there are still improvements with 20% being better than 40%. I wouldn't recommend going lower than 20% since Roadster Storage Mode is 20%, power is limited below 15%, and it's a good idea to have a buffer as reserve. A good rule of thumb for an ideal charge percentage is 15% SOC + your expected daily range.
 

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