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What should my ideal charge percentage be?
- Thread starter Al Sherman
- Start date
Not a problem.
There is no real ”to low” in a Tesla so single digit numbers are safe.
We get less degradation from time by using lower SOC but the big gain is from 55% and below.
That is where our M3 LR spends most of the time since new. I basically set it at 50% and charged up above that only when needed and just in time to leave. The car is coming up on 2 years old (Feb) and about 15k miles. It has been in hot temps since new which are worse for the pack. Overall degradation is less than 1% when I last checked it.
By comparison, my MY LR was at over 4% at a younger point in its lifespan (7k miles and 9 months). That was going with Tesla's spec of charging to 80/90% daily. The Y was driven in a comparatively cooler, but still hot, climate: Florida vs Texas. I sold the Y and it is now over 7% degradation and 60k miles.
2020 MSLR+ here, with 50k miles.
The car has a handful or superchargers (2MWh total). Charging at home every day to 60% (14MWh total). For road trips to 90%. Never above 90%, never below 10%. The cycles are mostly 50%-60%. The garage is about 75’F, consistently.
I am using “scan my Tesla” with OBD. Would appreciate help with:
1. It shows 212 discharge and 221 charge cycles. How do I explain that?
2. It shows 91.7kWh nominal full pack. Is the 5kWh reserve on top of that or included? If it is included then that is almost 9% degradation for 3 years only. Given that I was taking care of it, it seems rather high. Am I doing something wrong? Is the daily “top on” bad?
Thank you!
The car has a handful or superchargers (2MWh total). Charging at home every day to 60% (14MWh total). For road trips to 90%. Never above 90%, never below 10%. The cycles are mostly 50%-60%. The garage is about 75’F, consistently.
I am using “scan my Tesla” with OBD. Would appreciate help with:
1. It shows 212 discharge and 221 charge cycles. How do I explain that?
2. It shows 91.7kWh nominal full pack. Is the 5kWh reserve on top of that or included? If it is included then that is almost 9% degradation for 3 years only. Given that I was taking care of it, it seems rather high. Am I doing something wrong? Is the daily “top on” bad?
Thank you!
The largest source for difference between ”In” and ”Out” is probably that the battery efficiency is not 100%.
If you charge 100 kWh, the battery will not deliver 100 kWh.
The efficiency is lower at lower cell temperatures, so the delta will increase with low cell temps.
(Self discharge and cell balancing will also cause losses that’s not messured but fir modt people this would be low numbers. Often have the car above 80% will increase the self discharge and often above ~90% will increase the balancing losses. Remember that these are small losses so not important but could explain differences between different owners if you start to compare).
I had 2.5 years of logged data on my M3P but I can not reach it after the switch to the MSP. Might still be there, but not easy available today. I’ll try to find data from that one before I sold it.
My MSP has 3247 kWh charge total, and 3117 discharge total. But it is parked with 34kWh total remaining. (Charge total includes the regen).
This makes the delta about 3% so far. The car is ~8 months since build, and 11 K km.
Also remember that the energy stored in the battery give an extra difference, specially early in the cars life. Fully charged we have 95-99 kWh more charged than discharged.
SMT do calculate and present some data by itself, that is not BMS-data.
The # charge cycles is the total energy divided by the Nominal Full Pack (if they did nit change the principle for this) but acutalky it should rather be divided by the initial capacity. As the NFP is an estimate that can change, this number will change as a result. This will mean that the charge cycle changes and would get lower when the BMS estimate for NFP increases. Charge cycle numbers is handy but have those limitations so looking at total charge and total discharge will take the induced issues away.
Yes it is included. Nominal full pack is “total”.
Did you charge to 60% daily from day one or did you charge higher earlier?
60% is on the edge between ”good” and ”bad” so you might have had a slightly higher calendar aging initially.
If we assume an 25C average cell temp the calendar aging should be about about 4.5% for 10 months, which calculates to ~ 8.5% after three years using the graph below.
(Calendar aging is reducing the rate with time). 5% for one year will be square root (3) x 5 for 3 years.
Your average SOC would be lower, depending on when in the day you charge and the normal end of day SOC.
So you probably have slightly less calendar aging but a (1-2?) percent cyclic aging, that set your toral degradation to a out 9%. Not bad at all for ypur car, and just about as expected.
If you had charged to 50- (max) 55% instead, and charged late you would have been at about square root (3) x 3 = ~5% calendar aging so maybe 6% total today.
Thank you - very informative!
The car was set to charge to 60%, starting at 10pm every day, since the beginning.
Interestingly, looking at TeslaFi graphs, I should be having only about 5% degradation. Hence, my concern.
Do you think I should go for less frequent charging and deeper cycles? E.g. from 50-60% to 30-50%?
What initial capacity did you count with for the 2020 LR? 102.4?
I know its not the same pack as the refresh so…
Anyway, Tesla use a lower capacity than the max battery capacity as the upper limit to reach full (advertised) range. On model 3/Y it has mostly been about 2% or so.
So for example a 100kWh battery will show full range until it estimates the battery capacity to 98 kWh. The degradation threshold hides degradation.
Thats model 3/Y values, and the new S Palladium seems about the same or slightly more.
Which means that the degradation range wise will hide the same amount of degradation as the degradation threshold is lower than the new capacity.
I use teslafi and it has quite a few issues fir the degradation tracking.
You can see the starting range (which from a few reasons can differ from the full range.
So if you have full range when you get teslafi, you will see the degradation but without the hidden part from the part above the degradation threshold.
My car started the life showing ~ 95.7 kWh with a full pack when new of 99.4.
It the rised the cap to ~ 98 kWh where it still is. So from a teslafi point I have negative degradation.
Also, I tried to select the 19” wheels, which poppes the range to the full 637km. From that day my high range is 637km and despite my car has full range at the 560km with 21” it showes 13.9% range loss. Which is not really wrong in a actual displayed range but not even close to correct when it comes to degradation. My cas is s out the Plaids showing the highest capacity.
Picture doesnt paint a good picture, despite the fact that you probably have a hard time finding a Plaid with higher nominal full pack
Another issue is that Teslafi get the range wuite precise but the SOC rounded to whole numbers. The range calc mostly is off down about 3-7km from the real range (using BMS numbers).
So, if you your car started (in teslafi) 3% below full range, you first had the degradation loss of ~ 2% or so, and then your 3% below = started 5% below the full capacity, this will be the starting range.
If the car never displayed more, you can loose another 5% so you can be at 10% total capacity loss but teslafi will only show 5% range loss.
Scan my tesla and the use of real values is the best we can get. All OTA apps do the best they can to with the partly inadequate data. They sometimes do a quite good work with part of it. In many cases these show a wrong (way to low) degradation value if you use the percent data).
Contine as before.
It would be wise to not charge above 55% when you do not need more than 55%. If you really do not need much use the minimum setting of 50%
Deeper cycles is not really the way to go.
It would be possible to charhe more selldom but the calendar aging is relatively flat between 30-55% so you only ”win” when beeing below 30% which do not give you a long range. You actually do not reduce the calendar aging mu h but larger cycles wear more so you would loose range without a noticable reduction in degradation.
55% is the sweet spot, maximized range + almost the lowest degradation.
Charge late - not when arriving before the car is parked in the night but in the next morning so the car is at higher soc shorter time.
I always use 55% when not charging for a longer trip. I always connect the car each day at home. Charging set to commence in the early morning - late night to be ready shortly before the next days drive.
This means it might spend the night with 3, 7, 25 or 54% (whatever rests from the day before).
At my work Its parked one week at the time. Long drive there so I leave it at the rest level (often 10-20%) for the whole week and then I charge late just before going home.
My M3P had 492km out of 507 km so ~3% loss teslafi wise. The capacity loss from full pack when new was about 4.5%, but the nominal full pack mostly never git higher than 80.5-81kWh for most other cars so in that perspective ~ 3%.
I sold my M3P to a EV reseller. They checked my battery for degradation (using NFP Value) and also had a bunch of other with the same battery. My car was one of the first with the 82 kwh battery, so these was younger and mainly half the miles on the ODO.
All of these had 9-13% degradation and my 5% (they used the 82.1kWh full pack when new as the reference).
Its very clear that the mow SOC strategy will reduce the degradation quite much.
Thank you! I am not using TeslaFi; just their stats to compare. I use ScanMyTesla with OBD, that reads directly from the computer. Hence, no idea what the full pack was.
I also started TeslaMate recently (I am hosting it myself) and it estimated the full pack to be 95kWh; hence, my question about the 5kWh buffer. If that is the case, then I am in a pretty good spot, in terms of degradation. If I look at the 100kWh pack - then it is not so good.
Currently, I have 10pm start of charging and will switch to Time-to-leave schedule. That way I will keep it at lower charge for longer.
Thank you for the insights! Super helpful!
I also started TeslaMate recently (I am hosting it myself) and it estimated the full pack to be 95kWh; hence, my question about the 5kWh buffer. If that is the case, then I am in a pretty good spot, in terms of degradation. If I look at the 100kWh pack - then it is not so good.
Currently, I have 10pm start of charging and will switch to Time-to-leave schedule. That way I will keep it at lower charge for longer.
Thank you for the insights! Super helpful!
Yep!
To be perfectly clear most of the graphs shown is from batteries a few year and back (because a research report need to first have the cells available for test, then like one to two years for the test and maybe another half to one year to produce the report and get it accepted.
This report is from 2018 if I remember it correct. The tests in this case was about a half year so I guess the cells was taken from a 2017-2018 model S.
For the NCA cells from Panasonic they have been behaving about the same for ten years.
So just remember it like this picture vaöid as the principle for Panasonic NCA:
After several years the rate is very low but still about half at or below 55% compared to above.
The 55% safe number increases with calendar aging and decreases with supercharging. So after a cell has lost 5% from calendar aging, the safe level is 55/0.95 if no supercharging etc was done. To make it easy it might be wise to still use 55% and only charge more when needed.
Eric33432
Member
Why charge more than you need given all we know now?
I advise my friends who I have convinced to buy a Tessie, or who ask me, to charge the car every night to the level they need for the next day (not less than 50% since that is the minimum), to enjoy the car, and not worry about it.
When I was new to my MX I charged it to 80%, because that seemed to be what everyone said to do back then and with the limited knowledge I had I did not know any better.
As I got confidence I was not going to be stranded, and realized that for daily driving I usually only needed from 10 to 30% of the battery, I reduced it to 70% for a while, and then to 50% once I got the confidence to realize that 50% was fine for daily driving, and unless I know I will need more than that, such as a short day trip out of town, 50% is fine
For a road trip, I charge to 90% the night before, then whilst getting ready for the trip the next morning, bump it up to 100% and when I leave it will be somewhere between 95 and 100%.
Discussing the MX above. The M3 RWD is another thing.
Best Christmas wishes and Happy New Year.
I advise my friends who I have convinced to buy a Tessie, or who ask me, to charge the car every night to the level they need for the next day (not less than 50% since that is the minimum), to enjoy the car, and not worry about it.
When I was new to my MX I charged it to 80%, because that seemed to be what everyone said to do back then and with the limited knowledge I had I did not know any better.
As I got confidence I was not going to be stranded, and realized that for daily driving I usually only needed from 10 to 30% of the battery, I reduced it to 70% for a while, and then to 50% once I got the confidence to realize that 50% was fine for daily driving, and unless I know I will need more than that, such as a short day trip out of town, 50% is fine
For a road trip, I charge to 90% the night before, then whilst getting ready for the trip the next morning, bump it up to 100% and when I leave it will be somewhere between 95 and 100%.
Discussing the MX above. The M3 RWD is another thing.
Best Christmas wishes and Happy New Year.
Thanks a ton. I'm a newbie here so I can't like the post but it definitely is an amazing help.
I have written a lot about this during ~ three years. Most often with references and links to research reports.
So a search for “calendar aging” or something like that in posts from me, will result in a lot of info.
So looks like 35-55% range is the least followed by 55-95% if I'm reading right? With 5-25% being even worse.
I see your post now about 55% being your target now.
Does it depend on how much you drive a day? Meaning if you end day with 20% would you charge daily maybe to 65% or something? Thanks.
The cyclic aging is very small anyway.
If you look at the 5-15% line it looses about 17.5% for 3000 FCE.
Each FCE would be about 400km so the car would do 1.2 million km or 800K mi before loosing these 17.5%.
For a car driven normal annual range this would be about 0.3% degradation each year.
So that graph is easy to misunderstand. 5-15% is nor bad or dangerous.
Off course no one does, but if you would you would have about 2.5% calendar aging for the first year compared to the double if you go above 55%.
You can not save degradation by trying to reduce the cyclic wear in that picture.
I charge to 55% at any time thats enough until next charge. I did not select 55% before 50% to reduce low SOC, as low SOC down to 0% is not bad.
I mostly do not charge more than needed on a longer drive either.
Mostly arrive at ~10-15% at work and have it there until I charge for the drive home.
Also, I am not afraid to use 100% when needed. It do not wear that much.
Having SOC > 55% does.
My car is parked with about 19% at work right now. Charged to 100% before the drivre here due to 300km in extreme cold (-41C right now).
Eric33432
Member
aerodyne
2 of 3 EV's - Defect Free!
And I'm worried if the car gets below +40F....
Our average annual temp is below thatAnd I'm worried if the car gets below +40F....
(UMC connected to a car heater wall outlet on timer. I start it from time to time to keep the battery from getting too cold. Tesla says not to lesve the car for more than a day at below -30C so a little heating wont hurt).
aerodyne
2 of 3 EV's - Defect Free!
I do the same for the same reasons. At 240V, 7 Kw, which for me is about 28 miles of rated range added per hour.
There is no need to change, and it does not matter how you AC charge.
Certainly no benefit at ambient temps to charging slower as you won't heat up the pack as much and will have a higher percentage of wasted energy just keeping the car awake.
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