Devil's Advocate - Charge it to 100%

[MXWing]

I wonder if OP is banned from his neighborhood buffets.

From my game theory point of view, I believe Tesla would have factored in the use case of cars always charged to 100 percent.

Battery management team would have planned for MTBF (mean time before failure) to after your warranty period so your battery will be worse off on average than managing it appropriately.

If you sell your car while under the warranty period, the buyer won’t know how you treated the battery unless the degradation was already substantial.

 

[longshot49]

All that said - I understand your point of view.

Performance car - might as well use every ounces available.

As long as this is an "informed decision" (I like the french expression "connaissance de cause") and the owner is okay with faster battery degradation, why not?

Personally - I don't. Car is plenty fast and I want it to last me as long as possible. And Tesla clearly doesn't want that either. Did I mention how much I *hate* not having full regen?

 

[seantay00]

Interesting perspective on the limited regen. I'm curious why this occurs at 90%, there is no way sudden braking with regen is going to over charge the battery 10%... why do they limit regen? I have grown to like the feel as well. Was annoyed the other day driving our XC90 as it just "keeps rolling forever".

 

[mike123abc]

The other issue is if you charge to 100% it takes a long time... It essentially trickle charges the last 10%. Then once you start driving it you have zero brake regeneration available. It is funny when you take your foot off the accelerator and your car keeps going when you are used to the one pedal driving - like you are on ice...

They also make it pop up warnings and try to get you to go back to 90%

 

[mike123abc]

Interesting perspective on the limited regen. I'm curious why this occurs at 90%, there is no way sudden braking with regen is going to over charge the battery 10%... why do they limit regen? I have grown to like the feel as well. Was annoyed the other day driving our XC90 as it just "keeps rolling forever".

It is somewhat limited... I suspect that it is because they only slow charge the last 10% if you use the wall adapter, and the brake regeneration would be too fast a charge. The wall adapter goes down to like 1kwh charge draw.

 

[seantay00]

I wonder if OP is banned from his neighborhood buffets.

From my game theory point of view, I believe Tesla would have factored in the use case of cars always charged to 100 percent.

Battery management team would have planned for MTBF (mean time before failure) to after your warranty period so your battery will be worse off on average than managing it appropriately.

If you sell your car while under the warranty period, the buyer won’t know how you treated the battery unless the degradation was already substantial.

Agreed. It's actually to Tesla's advantage to encourage owners not to utilize all their battery. Less warranty claims, also probably drives higher resale value of cars... a big selling point on vehicles. Wouldn't be surprised if they have some strategic reasons for the positioning as well outside of battery charging physics. They'd be foolish though to not design the car to support warranty on users charging to 100%, would become a PR nightmare.

 

[EIon Musl<]

The battery management system will not let you charge the batteries to the full 100% absolute power to protect the physical chemistry of the batteries. What you see on the screen is the relative power, so if it shows 100% then the absolute power is like really around 80%. That's why they can increase the range over the air because their collection of tesla owners data shows they can move the 100% bar further out to give us access to more power without degrading the batteries more than normal. Tesla says not to charge to 100% because you will not be able to use the full regen and you will put more wear on the brake pads, but usually you will use 5% to 10% electric of power before you use more of the brake pads on the highway. I charge to 90% every night since my plug is in the garage anyways when I come home, I drive 55 miles each weekday. I can set my inside cabin temp to 105 F when I'm at work. Also I can leave my sentry mode on. With these settings I lose about 1 mile each hour, sentry mode uses power specially in a parking garage with lots of activity waking it up, but worth it for the recordings.

 

[SageBrush]

so if it shows 100% then the absolute power is like really around 80%.

No, but you are welcome to look for a reference to back up your statement.

By the way: battery voltage, not power.

 

[MXWing]

No, but you are welcome to look for a reference to back up your statement.

I issued one of my very rare disagrees. This is talking out of your ass but passing it off as some kind of subject matter expert fact.

 

[ForeverFree]

It is somewhat limited... I suspect that it is because they only slow charge the last 10% if you use the wall adapter, and the brake regeneration would be too fast a charge. The wall adapter goes down to like 1kwh charge draw.

Yes, I believe that full regen charges at something like 60 kW!

 

[SageBrush]

Agreed. It's actually to Tesla's advantage to encourage owners not to utilize all their battery. Less warranty claims, also probably drives higher resale value of cars... a big selling point on vehicles. Wouldn't be surprised if they have some strategic reasons for the positioning as well outside of battery charging physics. They'd be foolish though to not design the car to support warranty on users charging to 100%, would become a PR nightmare.

This all presumes that a car's life is set by the warranty.

I expect 2x minimum, so I pamper my battery when it is no inconvenience to do so --- 99% of the time.

 

[SageBrush]

I issued one of my very rare disagrees. This is talking out of your ass but passing it off as some kind of subject matter expert fact.

Tesla charges a cell up to a bit over 4v at "100%."

Let's call it 4.05 v.
If that is only 80% then the "real" maximum voltage is 4.05/0.8 = 5.06 volts.

Go ahead, grab a Li-x cell and charge it up to 5 volts. I promise you a citation for social darwinism.

 

[willow_hiller]

Something also potentially worth noting. I don't believe this API feature works right now, but the Tesla API has a space for tracking the number of times your vehicle has charged to 100%.

It's called "max_range_charge_counter" on line 36 of the Charge State endpoint as documented here: Charge State

Tesla may be considering keeping a nice/naughty list with regards to how you treat your battery in the near future...

 

[MXWing]

Tesla charges a cell up to a bit over 4v at "100%."

Let's call it 4.05 v.
If that is only 80% then the "real" maximum voltage is 4.05/0.8 = 5.06 volts.

Go ahead, grab a Li-x cell and charge it up to 5 volts. I promise you a citation for social darwinism.

I disagree with what you quoted not your response.

You need more coffee this morning.

 

[turtlesz]

I don't worry about the degradation too much because even 2012 Model S seem to be holding up fine. Also I don't plan to keep any of my cars over 8 years. Doubt the future buyer would know/care how the battery was treated if you sell to a service like Carvana/Shift. However the reason I don't always full charge is the limited regen and the screen warning about full charge when you get in the car. It's just an annoying nag and wish it could be disabled. I do full charge anytime I plan a weekend trip or travel from socal to norcal. I'd rather charge at home and not waste money at the supercharger.

 

[mjmiron]

I bought my first 2013 S 85 as a CPO in 2017 and it started off as 232 miles when I charged to 90% and I had 56,000 miles on the car. Speed ahead to today I have 96,000 miles and at 90% it charges to 225. I did not loose that much battery degradation and only charge to 100% for long trips. I am with the folks who only charge to 90% I want longevity and new owners who purchase Tesla's that do their homework care about how much the car charges to. I have also noticed as the battery ages the first 15-20 miles burn off quickly if you charge to 100%. I am greatful to the blog it has so much good info I did a lot of research before buying. i just sold my S and getting a 2015 85D CPO, hoping process goes smooth fly out to Vegas to pick her up next week.

 

[SageBrush]

I disagree with what you quoted not your response.

I see. A little clarity would have been nice. E.g.,

"He is talking out of his ass ..."

 

[MXWing]

I see. A little clarity would have been nice. E.g.,

"He is talking out of his ass ..."

I didn't have my coffee either. That's my catch all excuse for all errors, mistakes, irritability, etc.

 

[Hank101]

Does Tesla state clearly anywhere what the routine (daily) maximum charge should be?

 

[TexasEV]

Something also potentially worth noting. I don't believe this API feature works right now, but the Tesla API has a space for tracking the number of times your vehicle has charged to 100%.

It's called "max_range_charge_counter" on line 36 of the Charge State endpoint as documented here: Charge State

Tesla may be considering keeping a nice/naughty list with regards to how you treat your battery in the near future...

Ever since the first Model S, a warning has been displayed if your charge is set to 100% for three days in a row. It's to remind people who set it to 100% for a trip and may have forgotten to set it back down. This counter is probably how the car keeps track.