I am doing as what SomeJoe7777 laid out. I do not plug in every day. I wait for the car to get down to different states of charge (be it 15% all the way up to 50%) and ensure it isnt plugged in so there is enough time for the BMS to capture this information be it 1-3 days between charges. Typical scenario is drive to work and come home would absorb 20% of the battery. Would let it sit in garage for 2-3 days without charging then do this once or twice more during the week and again allowing the car a day or 2 to record (no sentry mode on) and then charge the car. I also change the battery % for charging from 70-90%. I am trying to provide the variability needed for the BMS. Hopefully this provides further background. Is there something I am doing that could be causing this?
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How I Recovered Half of my Battery's Lost Capacity
- Thread starter SomeJoe7777
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TimothyHW3
Active Member
Yes, you didn't understand what to do.
The BMS doesn't need variability, the BMS needs consistency so that it can read what is going on. Keep charging, consistantly!, from 10% all the way to 90% (not in the middle, not to 50%, not to 70% etc.) and report back in 2 months. Wait to go down to 10%, plug in, charge to 90%, plug out and leave, repeat. Also make sure sentry and anything else that can keep the car awake (such as apps or services or smart summon) is off.
Why plug out and leave? I'm assuming if you don't schedule the charge and just let it charge when you get home for the night, once it hits the SOC it will go to sleep?
TimothyHW3
Active Member
You don't want to sit with high or low SOC for long times. It seems pushing it to 90% and starting right away or going down to 10 %and pluggin in is still ok for longevity, at least in my car it didn't really matter after 40,000km.
So you should time them so that you can plug in right at the low SOC and plug out when it hits 90% (play with the Amps limit or the schedule)
sitting at high or low soc for long times....what is regarded as long?
Once the car finished charging at 90% completion, is it ok to let it sit plugged in till the next day (a good number of hours or up to 24 hours?)
I thought you were supposed to let it sleep, especially at the top and bottom, for at least 3 hrs to balance itself?
TimothyHW3
Active Member
Don't think this is necessary. You don't drive 90% to 10% each day, do you? The car sleeps at random SOCs during the day anyways so this will be enough. Also, the car calculates the kWh added from 10% to 90% so they know what the car was reporting at 10% and 90%, it doesn't need to stay awake for these SOC. I also wouldn't let it sit at 10% or lower for hours, especially in the cold. I had to do it once because I had a meeting and nowhere to charge and after I came back it was almost down to 3% at 0C for about 1-2hours, because it cooled down.
That I will def regard as long, anything above 1-2 hours, def not overnight at such high SOC. Especially not at temps above 25C or about 80F.
Obviously I don't have any stats since you will have to have two cars observation over years, but that is what the battery university is telling us...
https://batteryuniversity.com/learn/article/how_to_prolong_lithium_based_batteries
Don't pay attention to Timothy, they obviously haven't read this thread to understand the methodology used to get the BMS to re-calculate the battery capacity more accurately.
You are supposed to let it sit, and sleep, at various different states of charge for hours. This means you have to make sure that everything that could keep the car awake is turned off. (Things like Sentry mode, third-party apps that keep the car awake, etc.)
Our temps are now around 10-15C in Scotland UK.
I thought it was fine to have the car with a soc of between 20-90%, even if it means sitting for several hours i.e. overnight up to 24hrs. But having the car at 90% for several days or weeks is not good; or having the car <10% or >90% for more than 1hour is not good.
TimothyHW3
Active Member
Sure buddy, just that I was actually explaining how the BMS calculation works months before this thread, and you were pushing disagree on every time if I remember correctly
And now you are the first one to "explain" the methodology. If I look back at your posts I will surely find one where you say to read the manual and keep it plugged in...
You don't have to let it sleep at 90% for hours that is certain. Since you still don't understand how the calculation works let me explain - it is pretty simple. The car measures voltage while charging, but it also double checks the voltage at various SOC when sleeping,this part is true.
But since the car knows the voltage at 90% when it charged to 90%, you don't have to actually leave the car at 90% - the car already knows that.
So the car does this:
Start at 10% - ok, we are at Vx and Vx is normally this kWh
End at 90% - ok we are at Vy and Vy is normally this kWh.
Let me deduct kWhend - kWhstart and get kWh added.
Then it cross checks inside the BMS what the kWh added should be and calculates the kWh difference and deducts it from the range.
There are actually apps that do exactly that on your phone, Google them. They measure the mAh added at different state of charges.
The main problem with degradation in these threads was not tso much hat they didn't let the car sleep - that is the smallest problem. The main issue is they were simply charging 70%-90% consitently "because the manual says so" and when I pointed out that problem, people like yourself told others not "to listen to me"
By charging to 70%-90% the car can't figure out where it is since the Voltage in that range is simliar. That is the main issue, not sentry or leaving the car awake (which is also problematic, but not the main problem)!
If you keep on charging 10%-90% and disable sentry, without bothering with anything else, you will be fine.
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TimothyHW3
Active Member
Depends on what you regard as good. The difference between 90% or >90% is so minimal, since Teslas charge to the top @ 4.2V, no top buffer, so I don't know why you would regard >90% differently as 90%.
Like I said, If I were you I would unplug at 90% and leave. You do like you want. This is what I do, I usually charge in the 10-90 or 20-80% range and am at measured 3.5% degradataion after 40,000km and have been down to below 0% at least 3 times and 2 times at 1-3km left so I know the BMS on my car is good.
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I regard 90% and >90% different, as simply Tesla's recommendations are 90% for daily charging at the top.
For long road trips fine to go >90% and theres consistent views about not letting it sit longer than say an hour in the top 10% extremes (i.e. 100% always drive immediately to drop the soc back down to atleast 90%). So with that in mind, i sense its fine to let it sit at 90% for a longer period i.e. a good number of hours, but not weeks.
That was my understanding and take on it. But again I appreciate there are also views that if one isnt using the higher soc at 90%, then worth considering in charging lower i.e. 80%.
Correct me if i'm wrong but I sense your view is don't leave it sitting at 90%, drive it immediately down to a lower soc i.e. 85%? But fine to leave it sitting at 80% for overnight or a good number of hours.
By comparison, my LR RWD with is showing CAC min 218.6 and max 219.5 in SMT. I'm at 9,628 miles and showing 77.0 Nominal Full Pack.
TimothyHW3
Active Member
Like I said, the difference will be minimal depending on how much km you drive.
I like to not keep the car in high SOC% at all. Anything above 4V I consider high. (4V is around 75% or so). So I try to charge to 80% when I don't need the car and to about 90% when I know I can drive away.
I sometimes charge to 65-75% depending on how much time I have.
I think the main thing is to not charge in small increments and mostly don't charge in high incremets where the Voltage difference is minimal (ie. 70%-90% like most people do) I have also observed that slow charging on DC (ie 50kW) also trips the BMS and messes up the range.
By the way, the theory that you have to keep the car at 90%, let it sleep and this will miraculously fix the range is also proven wrong by all the people who charged 70%-90% (mostly people who drive 50miles a day, go back plug in the car and forget about it) and still had range decrease.
That isn't the theory. You need to go back and read the first post to understand the theory that this thread covers.
I've always charged to 90% the majority of the time, delayed charging till 50/60%.
But having read the thread, i'm now trying larger discharges between 10/20% to 90%.
I've been trying to follow the recommendations on per this thread with regards to ocv readings and getting sleep at different soc. So planning on doing this for at least a month or so to see?
After this experiment, i'll probably move to 80-20/30% charge range and stay with that.
I just want to know if my rated range will improve or if what i'm getting is truly all degradation?
Low mileage M3P (3800miles and just over a year old).
At new was getting 279rmi @90% and est 311rmi@100%.
Now getting 269rmi @90% and est 299@100%.....and dropping week by week.
Based on Teslafi fleet the avg is at 305-306rmi@100%
Also, interested to hear about your observations on DC 50kW charging on how this trips BMS and messes with range?? Can you elaborate on this one? Although i've been home charging on L2 7kw.
I have in the past done a few DC 50kw sessions at public chargers; some of these are free charge stations for where we are. So still planning on using these, but curious to know what the issue is?
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TimothyHW3
Active Member
Not sure what the issue is, but it might have something to do with how long the cars keeps the battery warm. Normally on a Supercharger you charge in 30 minutes and you are gone and the battery cools down a little. On a DC 50 you charge longer and the heaters (motors) heat up the battery for longer periods, an hour, hour and 1/2 etc. Most of the time Model 3s don't get full 50kW on DC 50 anyways. Below 40% it is because of the voltage + stators heating the battery and taking 7kW. (so around 37kW is normal). And above 40% the stators again. So usually on 50kW you can expect anywhere from 35kW to 45kW, and shortly 49kW if you manage to heat up the battery somehow.
I have observed that on DC 50, when I don't charge to 90% but simply top up say 40-50%, this messes up the BMS and the cell imbalance.
@sonic88 @TimothyHW3
I have been daily charging to 90% and letting it sit at 70% roughly for a year. Except for trips where it has the whole range.
When I look at 100% SoC on app, it says 278miles. Some times it's 286miles.
I have a 2020 stealth.
I'm going to try to let the car see a bigger range this week. Like down to 10% and charge it up to 90% like timothy said.
Doesn't bother me much since I drive with energy % rather than distance so I only like to check for science.
I'll report back if I find Tim's method to be useful.
I have been daily charging to 90% and letting it sit at 70% roughly for a year. Except for trips where it has the whole range.
When I look at 100% SoC on app, it says 278miles. Some times it's 286miles.
I have a 2020 stealth.
I'm going to try to let the car see a bigger range this week. Like down to 10% and charge it up to 90% like timothy said.
Doesn't bother me much since I drive with energy % rather than distance so I only like to check for science.
I'll report back if I find Tim's method to be useful.
You'll never get the BMS to get the brick balancing to run that way. The formula is very clearly called out in the Model 3 Theory of Operations guide, which I assume you've read? The shunt resistors don't close unless: SoC > 85%, Vehicle State = Sleeping and ∆V > 5mV
It takes about 24 hours to reduce the imbalance by 1mV.
Spending some time at SOC > 85% is good for the battery.
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