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Free charging, would you charge to 90% regularly?

I've read the guidance on this, both from Elon and some of the studies on battery degradation.

General advice seems to be 20-80% SOC is the sweet spot to keep the battery in for optimal longevity, even though Elon says you can charge up to 95% SOC with no issue.

I have access to free charging at work a few times a week, and my thought is on those occasions to charge up to 90% so I have only a little top off to do at home.

The app and in car limit also has 90% in the 'daily' range.

What would you do?
 
There's a lot of debate over the "best" percent.

I opt to charge at home to 90%, but I don't charge every day. My parking battery usage is trivial, may be 2 miles per day.

On the road at Superchargers, I charge to whatever is needed for the next planned stop. More than that is just a waste of my time and of the Supercharger slot. That can be 65% or 100% or anything in between.
 

Tam

Well-Known Member
Nov 25, 2012
11,288
10,326
Visalia, CA
...Elon says you can charge up to 95% SOC with no issue...

Is this 90% tweet (not heard about 95%)?

"Not worth going below 80% imo. Even 90% is still fine. Also, no issue going to 5% or lower SoC."

See the tweet above that as the owner heard that Service Centers instruct owners to set it at 90% and she didn't believe it until she herself was told and she made a video about it then asked Elon.

upload_2019-9-13_11-54-0.png


I've also read several posts where the owners were slapped with the writings "poor charging habit" on their receipts for charging less than 90%.

Note that this is what we are told but it doesn't say which State Of Charge is best for minimizing degradation.

Since that's what Tesla wants, I'll follow with what Tesla wants.
 
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I've read the guidance on this, both from Elon and some of the studies on battery degradation.

General advice seems to be 20-80% SOC is the sweet spot to keep the battery in for optimal longevity, even though Elon says you can charge up to 95% SOC with no issue.

I have access to free charging at work a few times a week, and my thought is on those occasions to charge up to 90% so I have only a little top off to do at home.

The app and in car limit also has 90% in the 'daily' range.

What would you do?
I have a 10 mile commute to work and have access to 240v outlet designated for BYOC for EV charging.

07/2018 - Delivery M3 LR RWD
12/2018 - 310 @ 100% SOC
05/2019 - 304 @ 100% SOC (w/ 5% boost should be closer to 325 by this period)

The difference is that I started charging often at work often from 70%~80% to 90% around February because my work schedule changed. I did try to follow some recommendations posted by others on the forum and have seen my range fluctuate which leads me to conclude that I need to cycle a few battery balancing initiatives to obtain the honest range.

From my personal experience, if you decide to charge everyday and have a short commute, you'll have a pretty unbalanced battery. I will probably try to get it to balance/calibrate again before my next service - rotate tires (currently at about 7500 miles so far).

Hope that is of some insight. Perhaps others who are in a similar situation can share their experience as well.
 
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Tam

Well-Known Member
Nov 25, 2012
11,288
10,326
Visalia, CA
...the manual...says nothing about discharging to a certain level...


In general, Tesla's battery is very robust so you should not be overly concerned with charging habits. Otherwise, Tesla Service Center does give you a routine recommendation of 90% on a written receipt as previously discussed above.

The 95% in the tweet above is the answer to an exceptional need and it's not about a routine daily recommendation.

If you need 100% charge while on a road trip, then do it.

If you need 95% charge because your daily commute needs it, then do it.
 
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dmurphy

Active Member
Supporting Member
I leave mine plugged in at home, charged to 90% daily. Still early days, 6226 miles on the odometer, but the battery is actually trending just perfectly fine. I actually expected an early 3-5% drop but haven't seen it.

Is it possible I'm not treating it perfectly? Yeah, maybe. Do I really care with numbers like this? Nah. I'm gonna do what's most convenient for me, and that's 90%.
IMG_EC5084B26CEB-1.jpeg
 
1. I don't know anything more about Tesla's battery technology than what I glean from reading.
2. I'm not an electrical engineer.
3. I'm not going to pay for your replacement battery if my advice is bad.

In spite of my lack of credentials, I would suggest that you charge to 80%, then bump up to 90% an hour before you plan to leave. So, depending on your commute, you'll probably end up with 75-85% when you get home.
 
I also commute about 100 miles per day and have 2x HPWC at work set to 40 amps. I have my P85D set to 90% and charge to that daily. I have noticed small amount of range loss but nothing to care about. Range loss also comes with age/miles as we know and I put about 40k miles on my car in the past 12 months. I do not have a charger at home so work and Superchargers are the only way I get the Juice. Ill HPWC all week then supercharge 1x per weekend, normally on the urban (72Kw) chargers close to my house. Always set to 90% unless in a trip Ill charge to whatever is needed to get to next supercharger/destination charger at hotel, no point to clog up supercharger or waste time when car is going to sit overnight anyway.
 
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Why the caution if Tesla is recommending charging to 90%?

Not a criticism, just seeing conflicting guidance/opinions around this.


Charging to 80% gives you a buffer to precondition the car to 90% or less in the morning.

Charging a little before leaving warms up the battery and the car is comfortable when you leave.

And doing it before leaving means it is not sitting at a high state of charge for long periods of time.

Great for those cold winter mornings or hot summer days.

The Tesla app makes it easy to up the charge rate while making coffee in the morning.

Dahl the batttery researcher and expert recommends 80%.

Elon figures that for most people it is OK to go more and I respect that but I keep my vehicles a Loooong time.

My last vehicle that I got rid of had 300,000 miles on it when I let it go.

My Tesla is a keeper. It puts a smile on my face every time I drive it.
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,178
Canada

That 95% was in response to a new SR+ owner (240 miles RATED range) with a 160-mile daily commute that wanted some "wiggle" room but was worried about charging to 100% daily.

"my commute is 80 miles each way, which leaves me little wiggle room for sentry mode/fun driving/errands"

Elon's response taken out of context isn't advice for everyone to charge to 95%. If you need it because you need it, then do it and it's not a big deal. But, it could be "a" deal. I would charge to what you need for daily use and a small buffer.

If you need 200 miles of the 240 rated range every day, then I'd be pushing 95% too (or getting an LR). That 160-mile commute could easily use 200 miles of rated range. It's likely at least 180, which is 75% of your battery. Keep a 20% bottom buffer and you are looking at 95% just to get back home with 20%.

If you are using 10-20% daily, there's no need to go to 95% and the "it's not a big deal. charge to 90% to 95%" isn't directed at you.

Also note how Elon said 90-95% ... why a range? Because lower is better and you should choose the lowest that you are comfortable with if you are worried about the health of your battery (which the tweet Elon was responding to was).
 
I've read the guidance on this, both from Elon and some of the studies on battery degradation.

General advice seems to be 20-80% SOC is the sweet spot to keep the battery in for optimal longevity, even though Elon says you can charge up to 95% SOC with no issue.

I have access to free charging at work a few times a week, and my thought is on those occasions to charge up to 90% so I have only a little top off to do at home.

The app and in car limit also has 90% in the 'daily' range.

What would you do?

If it's warm enough that you use AC in the hottest part of the day I would not charge to 90% just because it's free (but I'd still charge to 80% and try to run cabin overheat protection on the free electricity, or maybe turn the AC down further to try and match the charge rate you are getting). Between there and about 50F I'd charge to 90% on the free electricity. If it's colder than 50F I'd charge to 100% on the free electricity (and set a climate timer for 15 mins before you plan to leave or manually turn on the climate controls with the phone app before you plan to leave)

On the days you don't get free electricity I would charge to a lower number like 70% if you can get away with it. Mix it up, but don't charge more than you have to when it costs you more.
 

darth_vad3r

Well-Known Sith
May 6, 2019
1,574
1,178
Canada
I also have a short commute, about 10 miles a day.

OTOH, the manual says the battery is happiest when plugged in, says nothing about discharging to a certain level before plugging in...

Right, it just says there's no advantage to waiting til it's low to plug in, nothing about the level, but something about it indirectly since if you charge daily to X% and use Y% per day, then it's saying to charge when you hit X-Y every day, your charge level :D (X% is the recommended daily range of 50-90%)

"There is no advantage to waiting until the Battery’s level is low before charging. In fact, the Battery performs best when charged regularly"
--Tesla Manual

With a 10-mile a day commute, and access to charging at work, couldn't you just charge to 80% easily at work a few times a week and still be fine? Maybe charge up to 90% on the last day before the weekend to get the most bang from your free electrons?
 
Also note how Elon said 90-95% ... why a range? Because lower is better and you should choose the lowest that you are comfortable with if you are worried about the health of your battery (which the tweet Elon was responding to was).


I think Elon is sometimes misunderstood or taken out of context.
I think what he said was it is OK to charge to 90% if and when you need to.
That also implies that if you don't need the extra range charge to something less like 80%
Any li-ion battery should not sit at a high state of charge for long periods of time.
If you charge to a high rate like 90% or more drive it soon after charging.
A high rate of charge should only be used on trips and only when necessary.
Like you said. Lower is better. If you can live with 80% charge to 80%.
 

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