Welcome to Tesla Motors Club
Discuss Tesla's Model S, Model 3, Model X, Model Y, Cybertruck, Roadster and More.
Register

Battery Charging Conflict - Owners Manual vs. Service Tech

Had my Tesla Y for 2 months. Is not a daily driver. Set charge max at 76%. I leave it plugged in unless driving. I talk with a Tesla Service Tech who told me his cousin and uncle both purchased Model 3's. Cousin charges to 90% and only plugs in when battery gets down to 10%. Uncle charges to 80% and leaves it plugged in when not driving. After 4 years uncle had lost 25 miles of battery of battery power. Cousin has not lost any battery power miles. Service tech told me this is why you do not want to be charging your battery all the time. Tesla manual says to leave it plugged in when not driving. Service Tech said to ignore what the manual says. What should I do charging wise????
 

mswlogo

Well-Known Member
Aug 27, 2018
8,249
7,752
MA, NH
Only letting it run down to 10% and 90%?for extended times is not good.

Could be the 10% - 90% might be better calibrated. But I don’t believe he lost no miles. Model S/X seem to have much higher degradation than 3/Y.

Plugged in or not really doesn’t matter. It’s your average state of charge that matters. Leaving at ether extreme is not good on regular basis for any extended time.

It’s also stupid to just let the car run down to 10%.

I charge to 80%. Never dip below 20%. Sometimes I leave plugged in, something not. I have charged to 100% a few times and SC many times. Degradation is in low single digits (miles) after 2.5 years 25K miles.
 
Upvote 0

jcanoe

Well-Known Member
Oct 2, 2020
5,979
6,647
Maryland
Had my Tesla Y for 2 months. Is not a daily driver. Set charge max at 76%. I leave it plugged in unless driving. I talk with a Tesla Service Tech who told me his cousin and uncle both purchased Model 3's. Cousin charges to 90% and only plugs in when battery gets down to 10%. Uncle charges to 80% and leaves it plugged in when not driving. After 4 years uncle had lost 25 miles of battery of battery power. Cousin has not lost any battery power miles. Service tech told me this is why you do not want to be charging your battery all the time. Tesla manual says to leave it plugged in when not driving. Service Tech said to ignore what the manual says. What should I do charging wise????
These examples are not a good comparison of charging routines and battery capacity loss because the driving routines of these two Model 3 owners are almost certainly not the same. When plugged in the Tesla vehicle will only charge as needed to top up the battery. I don't charge every day, probably 4 or 5 times per week. I rarely charge above 90% and have not observed the battery at less than 30%.
 
Upvote 0
You have to understand that the manual doesn't necessarily give its recommendations based on pure battery longevity. There are other factors they must take into account, like people always having enough battery to go where they want to go, simplifying ownership. Plugging every day makes sure you never forget. Suggesting 90% makes sure you have plenty every day. Some of that fits with good battery research: smaller depths of discharge/recharge are better. For the rest, there are many other factors that affect degradation, like battery temperature for example, that's it's tough to compare each other's experiences unless all variables are described. There's all sorts of people saying all sorts of things based on their sometimes limited understanding of what is really happening. I am also not an expert so take what I say with some skepticism. I suggest you read the excellent threads in the model 3 battery subforum and get an understanding by yourself.
 
Upvote 0
There is a LOT more that goes into both calculating and realizing possible causes for battery degradation.

The first scenario is not good. 90% is ok but not leaving it plugged in and taking it down below 20% regularly are both things that could contribute to higher rate of degradation.

Supercharging can also cause faster degradation if it is done with high frequency.

Calculating degradation is also challenging because one cannot simply go by the range displayed on the Tesla screen. That range will change based on driving habits and is only an estimation.

The Tesla BMS is very very good at keeping the battery in good health. You should always leave it plugged in when your not charging because it will condition the battery more aggressively than if you leave it unplugged. It doesn't charge the car continuously. When plugged in it will use AC power to condition the battery and the car.

Drive more and worry less. The only thing you need to remember with a Tesla is always leave it plugged in when not driving (if possible/reasonable), don't charge above 90% frequently and don't run it below 20% frequently. Otherwise it isn't worth obsessing over IMO.
 
Last edited:
Upvote 0

Rocky_H

Well-Known Member
Feb 19, 2015
8,324
10,695
Boise, ID
After 4 years uncle had lost 25 miles of battery of battery power. Cousin has not lost any battery power miles.
There are two separate things here, which I think are getting smooshed together as one thing and getting confused.

I would bet that there really isn't that much difference in the physical status and energy storage of those two batteries. But the software of the Battery Management System that uses algorithms to try to read the amount of energy? That can get confused and out of sync pretty easily with certain things people do with their charging and how they leave the state of charge. A lot of that comes down to "visibility".

If a car is left sitting at almost the same state of charge all the time, like your 80% case you mentioned, the system's estimation doesn't have much variation of voltage to look at. It looks the same all the time, and the estimate drifts more and seems to lose a significant amount of energy. A battery that gets exercised more, to go to high and low states of charge, lets the car's software "see" the high and low ends and kind of does more of a "true up" to tune that estimate in more accurately on a pretty regular basis.

So I would say that while the 10% to 90% behavior is harder on the car and probably slightly more damaging, it's simply keeping the estimate more accurate. The constant 80% is generally healthier, but is getting a very fuzzy estimate, which isn't really a bad thing for the car; it just makes owners really uncomfortable.
 
Upvote 0

mswlogo

Well-Known Member
Aug 27, 2018
8,249
7,752
MA, NH
There are two separate things here, which I think are getting smooshed together as one thing and getting confused.

I would bet that there really isn't that much difference in the physical status and energy storage of those two batteries. But the software of the Battery Management System that uses algorithms to try to read the amount of energy? That can get confused and out of sync pretty easily with certain things people do with their charging and how they leave the state of charge. A lot of that comes down to "visibility".

If a car is left sitting at almost the same state of charge all the time, like your 80% case you mentioned, the system's estimation doesn't have much variation of voltage to look at. It looks the same all the time, and the estimate drifts more and seems to lose a significant amount of energy. A battery that gets exercised more, to go to high and low states of charge, lets the car's software "see" the high and low ends and kind of does more of a "true up" to tune that estimate in more accurately on a pretty regular basis.

So I would say that while the 10% to 90% behavior is harder on the car and probably slightly more damaging, it's simply keeping the estimate more accurate. The constant 80% is generally healthier, but is getting a very fuzzy estimate, which isn't really a bad thing for the car; it just makes owners really uncomfortable.
Not enough info. Someone can default to 80% daily but still run it down and go over 80% enough to keep BMS accurate. That’s basically what I do. I might charge to 100% once every 3 months. 90% the morning of a longer trip. And will run it down to 20%.

Or they could be going to 80% to 60% and never go over and have poor calibration.

Not enough info.

Since it is normal to lose a modest amount the 80% case might be accurate. Because I don’t believe the 10% - 90% lost nothing. Although it is possible their average SOC was still ideal. Again way to little info. When they charged to 90%, how long did it stay at 90%. If they drained to 11% how long did they leave it like that.

Tons of info missing.
 
Upvote 0

jjrandorin

Moderator, Model 3, Tesla Energy Forums
Moderator
Nov 28, 2018
15,774
20,459
Riverside Co. CA
Had my Tesla Y for 2 months. Is not a daily driver. Set charge max at 76%. I leave it plugged in unless driving. I talk with a Tesla Service Tech who told me his cousin and uncle both purchased Model 3's. Cousin charges to 90% and only plugs in when battery gets down to 10%. Uncle charges to 80% and leaves it plugged in when not driving. After 4 years uncle had lost 25 miles of battery of battery power. Cousin has not lost any battery power miles. Service tech told me this is why you do not want to be charging your battery all the time. Tesla manual says to leave it plugged in when not driving. Service Tech said to ignore what the manual says. What should I do charging wise????

Not getting into this debate itself because its happened ( repeatedly ) in the model 3 subforum to the tune of at least one thread of 250 pages long.

What I wanted to say after reading this is.....

Does it not seem strange to you that a tesla service technician is telling you this in the forum of "Telephone game"? Not " I recommend", but " I have a cousin and uncle who did XXX" (meaning THEY are not making any recommendation to you themselves)?
 
  • Like
Reactions: sleepydoc
Upvote 0
Yes that does seem strange. I guess it’s an inexperienced tech 😂

Regardless I don’t even look at the range. I have mine set to show SOC.
The conversation took place at the Tesla Service Center while I was in the waiting area. I had asked the service rep if he had a Tesla. He said he had a Y performance and he had just ordered a 2022 model. I told how I was charging to get his feedback on how I was charging and that's when he informed me about his cousin and uncle charging their Model 3's. I was surprised he contradicted the manual. They had a new 2022 Plaid on the floor for sale. He told me that particular car does 0-60 in 1.9 seconds. To your point about strange, could be so.
 
Upvote 0
Not enough info. Someone can default to 80% daily but still run it down and go over 80% enough to keep BMS accurate. That’s basically what I do. I might charge to 100% once every 3 months. 90% the morning of a longer trip. And will run it down to 20%.

Or they could be going to 80% to 60% and never go over and have poor calibration.

Not enough info.

Since it is normal to lose a modest amount the 80% case might be accurate. Because I don’t believe the 10% - 90% lost nothing. Although it is possible their average SOC was still ideal. Again way to little info. When they charged to 90%, how long did it stay at 90%. If they drained to 11% how long did they leave it like that.

Tons of info missing.
Well put. Thank you!
 
Upvote 0
Yes that does seem strange. I guess it’s an inexperienced tech 😂

Regardless I don’t even look at the range. I have mine set to show SOC.
There are two separate things here, which I think are getting smooshed together as one thing and getting confused.

I would bet that there really isn't that much difference in the physical status and energy storage of those two batteries. But the software of the Battery Management System that uses algorithms to try to read the amount of energy? That can get confused and out of sync pretty easily with certain things people do with their charging and how they leave the state of charge. A lot of that comes down to "visibility".

If a car is left sitting at almost the same state of charge all the time, like your 80% case you mentioned, the system's estimation doesn't have much variation of voltage to look at. It looks the same all the time, and the estimate drifts more and seems to lose a significant amount of energy. A battery that gets exercised more, to go to high and low states of charge, lets the car's software "see" the high and low ends and kind of does more of a "true up" to tune that estimate in more accurately on a pretty regular basis.

So I would say that while the 10% to 90% behavior is harder on the car and probably slightly more damaging, it's simply keeping the estimate more accurate. The constant 80% is generally healthier, but is getting a very fuzzy estimate, which isn't really a bad thing for the car; it just makes owners really uncomfortable.
Very true, Thank you
 
Upvote 0
This could also be luck 'o the draw - one battery manufactured with slightly better components than the other. All batteries are not made equal. And the sample size is too small to assume anything from the results.
Very good point, Thank you!
These examples are not a good comparison of charging routines and battery capacity loss because the driving routines of these two Model 3 owners are almost certainly not the same. When plugged in the Tesla vehicle will only charge as needed to top up the battery. I don't charge every day, probably 4 or 5 times per week. I rarely charge above 90% and have not observed the battery at less than 30%.
Yes, Thank you
 
Upvote 0
Agree with many of the above comments. In general, the data is pretty clear that 90-10 charging pattern is harder on the battery than a 80-20, etc. The battery will also age faster when stored at a higher state of charge and/or temperature vs a lower SoC and/or cooler temps. Then there’s the effect of super charging…
 
  • Informative
  • Disagree
Reactions: Rocky_H and mswlogo
Upvote 0

mswlogo

Well-Known Member
Aug 27, 2018
8,249
7,752
MA, NH
Yes that does seem strange. I guess it’s an inexperienced tech 😂

Regardless I don’t even look at the range. I have mine set to show SOC.
I always find it ironic folks keeping their car in % charged instead of “estimated” miles left.

If I charge every day to 80% and I see 326 miles I know things are in good shape. And I expect that number to drop over time.

If one day it shows 250, I know something is dreadfully wrong.

But if I just continues to show 80% I’d never know, until it’s too late, probably in the middle of my trip on the side of the road.

Listing miles left is a good daily diagnostic.
 
Upvote 0

Rocky_H

Well-Known Member
Feb 19, 2015
8,324
10,695
Boise, ID
I was surprised he contradicted the manual.
It's not contradicting. It's just talking about two different things that are for different purposes.

One of the purposes of what Tesla has published in the manual...is to sell cars. It is NOT to do what is the most ideal, healthiest, least degrading thing for the battery. For THAT recommendation, it would say something like "Leave the car set at 50% and never drive it." You can sure avoid a lot of degradation that way, but it's not a realistic use for a car, and if they told people that, no one would want to buy one.

So they have to advise something that gives people confidence they can use the car. One of the things the advice is trying to do is make sure people have enough range for their daily use, so they don't suddenly get into a bind of not being able to drive somewhere they need to, and then they get angry and tell all of their friends that this EV stuff is useless garbage. So they have to strike that balance of recommending people to avoid some of the most extreme things that are most harmful to the battery, while still having enough charge to be practical enough to be used as a car.

In other words, Tesla can't publish thousands of different versions of the manual to hand out individually to thousands of unique people with thousands of unique use cases to give the most tuned recommendation for THEIR specific use case. They have to publish one recommendation that is decent and OK for everyone, but probably won't be best case.
 
Upvote 0

Products we're discussing on TMC...

About Us

Formed in 2006, Tesla Motors Club (TMC) was the first independent online Tesla community. Today it remains the largest and most dynamic community of Tesla enthusiasts. Learn more.

Do you value your experience at TMC? Consider becoming a Supporting Member of Tesla Motors Club. As a thank you for your contribution, you'll get nearly no ads in the Community and Groups sections. Additional perks are available depending on the level of contribution. Please visit the Account Upgrades page for more details.


SUPPORT TMC
Top