What should my ideal charge percentage be?

[gaswalla]

I understand that the best battery health is when the state of charge avoids extremes (0-10% or 90-100%)... hence the teaching of keeping the battery at 50%.. but that means 50% average SOC.. not starting at 50% and letting it go down from there. I would think that someone that does very little driving would do well with charging to 60% and running it down to 40%.

Comments?

 

[djp]

I understand that the best battery health is when the state of charge avoids extremes (0-10% or 90-100%)... hence the teaching of keeping the battery at 50%.. but that means 50% average SOC.. not starting at 50% and letting it go down from there. I would think that someone that does very little driving would do well with charging to 60% and running it down to 40%.

Comments?

The US Army study found that cycling between 0% and 50% was better for battery life than cycling between 25% and 75%, especially in warm temperatures. The lower the average SOC the better (as long as you don't go to absolute zero).

 

[Kenne74]

Gaswalla,

You make a good point and perhaps moving the charge to 60 or 70% and not dropping below 30% might be the right way to set up the battery. Part of me wants to just set it at 90% and forget it, but I'm the guy who buys a car every 8-10yrs and I want this one to last, so I want to do everything I can to optimize my battery life.

Thanks.

 

[dsm363]

The US Army study found that cycling between 0% and 50% was better for battery life than cycling between 25% and 75%, especially in warm temperatures. The lower the average SOC the better (as long as you don't go to absolute zero).

In that study, were the cells thermally managed like Tesla does with its pack or would that not make any difference?

 

[djp]

In that study, were the cells thermally managed like Tesla does with its pack or would that not make any difference?

Yes, they did multiple runs at different temperatures. There was very little difference between a 50% charge and 75% charge at 70F, but a substantial difference at 105F. The cooling system in the Roadster kicks in above 105F.

 

[bob_p]

Why do we need the variable charging feature?

If it's to protect the battery - isn't that implying that even using the reduced mileage "standard" mode is also bad for the battery pack - and that the practical range of the car is not the 300 miles that was originally listed on the website, the 265 that was measured using EPA, or the 235-242 that most of us see with 85s - but something much, much lower?

Would be very useful for Tesla to provide owners more information on how to charge the car - and help extend the battery life - and even better - would be to modify the warranty plans to include a minimum guaranteed range for the batteries, as long as owners follow the recommended charging practices.

 

[steve841]

Why do we need the variable charging feature?

If it's to protect the battery - isn't that implying that even using the reduced mileage "standard" mode is also bad for the battery pack - and that the practical range of the car is not the 300 miles that was originally listed on the website, the 265 that was measured using EPA, or the 235-242 that most of us see with 85s - but something much, much lower?

Would be very useful for Tesla to provide owners more information on how to charge the car - and help extend the battery life - and even better - would be to modify the warranty plans to include a minimum guaranteed range for the batteries, as long as owners follow the recommended charging practices.

Does anyone actually get EPA rated miles?

Tesla is no different than any other car maker .... you sell the best case scenario.

My cell phone promises 5 days of standby ..... but I have to charge it every day.

That's life in the big city.

 

[rlang59]

I still think that this is something they should have put behind an advanced settings screen. I know that some enthusiasts have been asking for this feature but as Tesla grows they need to start to balance out what the vocal enthusiast community wants and what is easiest for the average consumer. To me this just adds too much confusion to what should be an easy plug it in experience. Yes I know you can just set it to 90% (which is what I will do).

 

[Todd Burch]

Does anyone actually get EPA rated miles?

I exceed EPA rated mileage nearly every day, with about 15 miles of interstate driving @70 mph and the other 75 miles on surface streets with speed limits between 35 mph and 55 mph. And that usually includes a few punches off the line.

 

[mknox]

I exceed EPA rated mileage nearly every day, with about 15 miles of interstate driving @70 mph and the other 75 miles on surface streets with speed limits between 35 mph and 55 mph. And that usually includes a few punches off the line.

Same here. Now that the weather has warmed up, I easily get 300 Wh/mi or less. I have a 80 mile roundtrip commute, with about 75% freeway where I drive anywhere between 65 and 75 MPH.

 

[Rodolfo Paiz]

I understand that the best battery health is when the state of charge avoids extremes (0-10% or 90-100%)... hence the teaching of keeping the battery at 50%.. but that means 50% average SOC.. not starting at 50% and letting it go down from there. I would think that someone that does very little driving would do well with charging to 60% and running it down to 40%.

Beat me to the punch, I was about to say exactly that.

 

[djp]

Beat me to the punch, I was about to say exactly that.

Keep in mind that Tesla locks out the bottom 4% as protection against bricking. If you run the car down to zero to the point where it shuts down and disconnects the battery, there's actually still some charge left. It's not easy to fully discharge a Model S battery, so you don't need to worry as much about the bottom end of the range.

 

[Rodolfo Paiz]

I'm not worried about bricking or zero charge. But using the bottom 10-15% of the battery is pretty hard on it, even more than using the top 10-15% of the battery capacity. And the poster to whom we were responding is using a charging setpoint of 50% for battery longevity... but if the goal is to take care of the battery's health in the best possible way and you're only going to use 30% of the range on a daily basis, charging to 50 and using the 20-50% range is not as good for the battery's lifespan as charging to 65 and then using the 35-65 range of the battery.

 

[montgom626]

Keep in mind that Tesla locks out the bottom 4% as protection against bricking. If you run the car down to zero to the point where it shuts down and disconnects the battery, there's actually still some charge left. It's not easy to fully discharge a Model S battery, so you don't need to worry as much about the bottom end of the range.

GM does something similar with the Volt.

 

[djp]

I'm not worried about bricking or zero charge. But using the bottom 10-15% of the battery is pretty hard on it, even more than using the top 10-15% of the battery capacity. And the poster to whom we were responding is using a charging setpoint of 50% for battery longevity... but if the goal is to take care of the battery's health in the best possible way and you're only going to use 30% of the range on a daily basis, charging to 50 and using the 20-50% range is not as good for the battery's lifespan as charging to 65 and then using the 35-65 range of the battery.

That's not what the data from the US Army study shows. They saw better battery life cycling between 0% and 50% than cycling between 25% and 75%.

No question you should charge higher if you need the range or want a buffer for unplanned trips, but in terms of battery life the lower the average SOC the better.

 

[gaswalla]

life was easier with the standard vs range choice

 

[brianman]

I still think that this is something they should have put behind an advanced settings screen. I know that some enthusiasts have been asking for this feature but as Tesla grows they need to start to balance out what the vocal enthusiast community wants and what is easiest for the average consumer. To me this just adds too much confusion to what should be an easy plug it in experience. Yes I know you can just set it to 90% (which is what I will do).

I think of this like the sunroof. I like the idea of "set it where you like, with high granularity" but adding notches for "typical settings" like the Pano would alleviate the "choices overload" part of the experience for some users.

- - - Updated - - -

Same here. Now that the weather has warmed up, I easily get 300 Wh/mi or less. I have a 80 mile roundtrip commute, with about 75% freeway where I drive anywhere between 65 and 75 MPH.

I had a feeling the word "exceed" was going to get into trouble quickly. I read Todd's "exceed" as "use more than" not "use less than". I suspect you read the opposite.

- - - Updated - - -

life was easier with the standard vs range choice

I disagree. I like my big gulp. And multiple volume levels instead of "high", "medium", and "low".

 

[Joel]

I disagree. I like my big gulp. And multiple volume levels instead of "high", "medium", and "low".

+1.

 

[mknox]

I had a feeling the word "exceed" was going to get into trouble quickly. I read Todd's "exceed" as "use more than" not "use less than". I suspect you read the opposite.

He said "exceeds mileage" which I interpreted to mean if the EPA on a car is 25 MPG and I actually get 27 MPG then I have "exceeded" the EPA rating because I'm getting "more" distance per unit of fuel... but I see what you mean :smile:

 

[roblab]

Does anyone actually get EPA rated miles?

I get ideal miles or better whenever I go on a long drive. And I get EPA miles running up and down our 1000' hill and down the valley several times a day. So, yes. Depends on how you drive. I rarely go over 60 mph (55 mph speed limit in Napa Valley, two lane hiway) though I have been known to get up to 110 passing 3 or 4 cars. and I don't live anywhere near a freeway. I keep telling people that you can get there just about as fast and a lot more safely and stress free by slowing down even 5 mph, but it is obvious that most people's vocabulary does not register the word, "slow". So, pardon. Forget I said anything. No. You cannot get EPA miles.