What should my ideal charge percentage be?

[gavine]

Does Tesla even allow full 100% charging of the battery? I've been of the impression that even when the meter says 100% full in a Tesla, just like the Focus EV, there's always a bit of capacity left that's unusable.

It is my understanding that the buffer is at the bottom with Tesla but not at the top. In other words, it will only discharge to a certain level which is above the minimum, but it will charge to the maximum if you select 100%, but I could be wrong.

 

[Vic_F]

Picked up my S75D yesterday and moved the max charge down slightly. How do you know what percent it is set at?

 

[GTIceman]

Picked up my S75D yesterday and moved the max charge down slightly. How do you know what percent it is set at?

Switch your units from miles to % under the settings and it will show you. Leave it on % and move away from miles entirely and embrace the EV world.

 

[TexasEV]

Switch your units from miles to % under the settings and it will show you. Leave it on % and move away from miles entirely and embrace the EV world.

Your display preference has nothing to do with embracing the EV world. The vast majority of Tesla owners choose to display rated miles rather than percentage.

It also has nothing to do with the question you were answering. The charging screen is always set by percentage. The tick marks are every 10% from 50% to 100%.

 

[GTIceman]

Your display preference has nothing to do with embracing the EV world. The vast majority of Tesla owners choose to display rated miles rather than percentage.

It also has nothing to do with the question you were answering. The charging screen is always set by percentage. The tick marks are every 10% from 50% to 100%.

Pretty sure that is not true, at one point the software did not show % on the charging screen if you had miles selected, the app operated in this manner. I see it when i change the driver profiles in my S as I use % and she uses miles.

As for the other comment, it was made in jest.

Also jealous of your former S color. I wish they still made the green.

 

[Danny_]

I used to think someone gave me wrong battery in my Tesla on both my Model S 70D CPO and my new Model X 75D, then I found out the "rated" and "ideal" settings button showing indeed did not have the range I thought I did ahah...

 

[4EVar]

Pretty sure that is not true, at one point the software did not show % on the charging screen if you had miles selected, the app operated in this manner. I see it when i change the driver profiles in my S as I use % and she uses miles.

As for the other comment, it was made in jest.

Also jealous of your former S color. I wish they still made the green.

I have mine set on %, so it shows % on the dashboard screen. Then on the MCU I have the graph showing which gives Range. So best of both worlds.

 

[Peter Lucas]

There is a very authoritative web site called "battery university". There, they refer to studies that demonstrate that maximum battery life will be obtained if you keep the battery between 60% and 75% charged, and chilled as much as possible. Charging above that, and discharging below that, and warm temperatures will reduce battery life. Of course the car isn't very useful if you restrict it's use to that narrow range. The point is that everything we do to get practical use from the car diminishes the battery life.
It is generally considered a reasonable compromise to keep the battery between 20% and 80%, whenever possible. Reserve higher charges and lower discharges only when necessary.

 

[arnis]

Do not agree. Battery University data on the website is outdated.
Any data that is 3+ years old can be outdated. Especially Li-ion battery tech.

 

[shred86]

Do not agree. Battery University data on the website is outdated.
Any data that is 3+ years old can be outdated. Especially Li-ion battery tech.

Can you point out what is incorrect on Battery University? I’m no expert on lithium ion batteries but I’ve yet to find any sources that refute or invalidate the data on Battery University. From the articles I’ve read and videos I’ve watched, it seems the new tech with lithium ions is in the additives they’re using to achieve higher Coulombic Efficiency (CE), which if anyone ever achieves a perfect 1.0, lithium ions would never degrade (in theory, other than some extremes conditions).

 

[arnis]

https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Even those cycle numbers are all way off compared to EV battery degradation data.

 

[shred86]

https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries

Even those cycle numbers are all way off compared to EV battery degradation data.

That is correct, they’re way off because they are using 11 different Li-polymer 1500mAh pouch packs used in mobile phones. These are not the same batteries used in Tesla’s or any EV for that matter. Mobile phone batteries are designed to last the average life cycle of a mobile phone (few years), which is drastically different than an EV battery. In other words, mobile phone batteries are much cheaper with lower CE values resulting in a faster rate of degradation. However, the concepts they’re showing still apply to lithium-ion batteries which the article you linked to explains some key points which you can even apply to your Tesla. That article was also updated 2 Feb 2019.

1. Don’t let the battery sit at a high SOC (>4.10 volts). Higher temperatures makes this even worse. Tesla also recommends against this, hence the reason they call it a “trip charge” for anything above 90% and “daily charge” for 50-90%. Tesla’s 100% SOC is ~4.20 volts (except for software limited batteries).
2. Lower depth of charge is better than bigger depths of charge, which is the point Peter Lucas was making above from the same article. Tesla recommends keeping the vehicle plugged in and not waiting to charge.

 

[Jtrader]

What is considered a “cycle”? Is plugging in at home every day to get from 50% to 75% a cycle, or is plugging in every other day to get from 25% to 75% a cycle?

 

[David99]

What is considered a “cycle”? Is plugging in at home every day to get from 50% to 75% a cycle, or is plugging in every other day to get from 25% to 75% a cycle?

A cycle is charging from 0% to 100% and then discharge again down to 0%. If you charge from 25% to 50% and then drive down to 25%, you need to do this 4 times to have a full cycle.

 

[Fiver]

A cycle is charging from 0% to 100% and then discharge again down to 0%. If you charge from 25% to 50% and then drive down to 25%, you need to do this 4 times to have a full cycle.

Just to expand on this a little. While batteries in general have a "cycle life", not all charge sessions have the same weight. While what David said above is correct for getting your total cycle count (which applies to everything from Teslas to phone or laptop batteries) in general for L-ion batteries cycling towards the middle of the charge range is better in the long run. To avoid confusion Tesla has steadfastly stated that charging to 90% daily will not harm your battery pack. While this may be true, pretty much anyone who's anyone in battery research agrees that cycling in the middle of your pack is better for longevity. (Including Elon, and Jeff Dahn, the Tesla battery guru.) If you know you only drive 50 miles a day, cycling from 60% down to 45% and back up to 60% will (in the long run) be better for the pack then charging to 90%, down to 75% and back up to 90%. The cycle count may be the same but the wear on the pack is less. If you know you need more range at some point, no harm in charging higher, even up to 100%. Just don't let the car sit at above 95% for many hours. "Range Charge and Go" should be your motto if you need every volt your pack can offer.


Or, just charge to 90% every day like Tesla says and don't worry about it. Honestly age seems to do more damage to cells then fretting over charge limits.

 

[Merle]

A cycle is charging from 0% to 100% and then discharge again down to 0%. If you charge from 25% to 50% and then drive down to 25%, you need to do this 4 times to have a full cycle.

That sounds about right.

For Macbook people, the Systems Report (Top Left Apple, About this Mac, System Report, Hardware then Power) will give you a cycle count. Even though I plug in my computer daily, my cycle count is 89, and not every time I unplug and plug it in! Based upon the sheer number of Macbooks out there with Lithium batteries, Apple may know a thing or two about power management.

 

[jerry33]

A cycle is charging from 0% to 100% and then discharge again down to 0%. If you charge from 25% to 50% and then drive down to 25%, you need to do this 4 times to have a full cycle.

Actually you would have to do more than four times because shallow charges are better for the battery than full charges. In addition, this misses the point that for a given amount of power output the cells heat up more below 50% than they do above 50%, so driving in the 90% to 50% range is better for the battery than driving in the 50% to 10% range. But most of this is immaterial in practice because Tesla has a real battery management system, and even if the battery is never used and kept at 50% age will still deteriorate it. There are also other factors such as how much you heat up the battery by frequent full power starts, etc.

 

[samppa]

so if I need to use about 80% of battery almost daily, what would be the best charge cycle?

I could use:
0..80%
10..90%
20..100%

 

[Fiver]

so if I need to use about 80% of battery almost daily, what would be the best charge cycle?

I could use:
0..80%
10..90%
20..100%

In general, probably 10-90%. Although if you are able to leave right when you get to 100% and drive it down then charging to 100% isn't all that bad either. It's charging past 90% (really charging past about 94%) and then leaving it sitting at a high state of charge for a long time that's bad.

Given the options, I'd say 95% to 15%, but make sure you get to 95% and leave. Don't charge overnight to 95% and have it sitting there for 8 hours before you depart at that SoC.

 

[JPoldo]

If several prospective Tesla owners read these threads, many would conclude charging is too complicated and dismiss the idea of owning an EV. If you simply follow the ticks and daily designation up 90% on charging slider, you should be fine for daily use. Let's not over think the issue. When near a supercharger, I often charge to 90% and arrive home with a high 80's level. Except for a trip, I'm rarely outside the 40-90% SOC. Switching display from miles to percent is helpful.