Charging below 50%

[AAKEE]

AAKEE - I've learned so much more about my battery from you since trading in my 2018 Model 3 LR AWD for a 2023 Model Y Performance last year. I felt the Model 3 battery degraded too much for me, because I normally kept it at 80% and often would charge to 100% for trips. Now, with my Model Y I keep it charged at 50% which I have discovered is fine for around town drives. For trips I go to 55% making sure my route has plenty of Superchargers. Surprisingly this seems to be working for me. Lately though my 9 month old Model Y hasn't been driven daily, sometimes it's weeks before I drive it. I have another vehicle that's kept outside and is just easier to access. If my Tesla every gets Summon again, then it will be easier to get in and out of my garage, I miss Summon. Anyway, am I doing things right keeping my Model Y plugged in at 50%, even though it's not driven much? I think I am but want to hear your thoughts.

Yes, I think that is good.you follow the advice from Tesla with ”plug it in” and still keeps the SOC at or below 55%.

I plug my car in everyday when I am at home (with charging schedule set to charge from 04-06 to be ready when first drive might happen.
For traveling when the car stays home, I tend to leave it not plugged knowing it will not be used for a week or so. If the SOC is low I happily leave it like that.
At work I park for a week each time, normally arriving with low SOC like 10-20%, not plugged in.

Charging to 100% for trips will not make any noticable degradation as long as the time with SOC > 55% is kept short.
Supercharging for sure causes wear (even if low SOC as you use gives the battery the possibility to recover from Supercharging losses).
So charging full before leaving home for a longer trip is possibly better than 55% and one Supercharging. Nothing to really think too much about, but I would use up to 100% when needed. (I do full charges quite often.)

I had > 30 full charges on my M3P with the 82.1 kWh Panasonic, and 55+ SuC sessions and still had low degradation (lowest on teslafi for the same car) after 2.5 years/66K km.

My Model S Plaid is one year since delivery and 15 months since the build date, 21K km.
I have 15 full charges and around 20 SuC sessions (18% Supercharging) and still has very low degradation, 97 kWh which is close to the starting /top value of 97-98kWh. Other cars in my region has been at ~ 94-95kWh after one year.

 

[AAKEE]

While the question is for @AAKEE, here is my 0.05 cents worth:

Jeff Dahn says 30% is ideal for nickel containing batteries when storing the car especially in Summer.

Actually, I think he does’nt state that.

He states to use 30%. That recommendation would probably be because he makes a judgement based on compromises, one being afraid of telling people to leave the cars with too low SOC so they do not start afterwards.

If he actually states that 30% is the SOC causing the lowest degradation he clearly is wrong when we look at all existing research for calendar aging.

He has been stating 70% or 75% begore as the best SOC to use, and in this case he is wromg if we look at what is best for the battery itself. He probably made a judgement with compromises from a tual range in the car etc.

In general I would state that Jeff Dahn either is very wrong in he’s research when he talks about cycles as the prominent degrading factor, or he is bad at expressing himself so we understand him like he means it.
Otherwise he would be not agreeing with the results from very very many research tests/reports.

I urge anyone that look into lithium battery tech not to rely on a single source. That of course includes me as a single source
Read several research reports.

If you find a disagreement, some of the reports are wrong (there is reports coming to strange conclusions but mist often looking at the test data itself it almost always matches the other testdata.


Jeff more or less always use terms hard to understand for the generic viewer and seen here is that people often did get what Jeff stated wrong.
Also, it would be more impressing if the statements matched the resesrch results.

Here is a few calendar aging tests.
There litterally is 100 showing the same thing and there is no tests that shows a increase below 30%.
These are all real tests some of them performed on real Tesla cells.
(There is many many more, but as they all show very similar results, we should if anything instead try to find several tests that would support that 30% is the best SOC from a calendar aging view.
(First we need to understand that a stTed value from for example Jeff might not be the SOC with the lowest calendar aging/degradation but a compromise that always will have the anser related to the input to the compromize and the weighing of the imputs.
One compromixe I could do would for example to advise my freiwnd/collegue about how to charge hea Tesla in the cold winter we have, knowing tje 200km he drives never safely can be driven to work with less than 100%. So the afvice is to charge to 100%.

The only problem is that you will need to manually charge the car to maintain 30%. If you don't use sentry and the car is asleep you maybe need to manually check once or twice a week to top up the charge to maintain 30%. Then when you need the car charge back to whatever is needed.

No, that is not right. Your building the case on that 30% is the best SOC, which it clearly is not. It is a good number bit the calendar aging teduces down to 0% (the true 0%, way below 0% on our screen).
BTW, if you think 30% is the best, it will be 27% displayed SOC (26.85% actually).

But it is not, so if you park with 30% or 27% and the car drains 0.1% per day it will be good as the SOC reduces all the time.
30% will be good for around 150-200 days or so.
A better thing would be to leave it at 10% or so, as long as the car do not stand for longer than 10 weeks or so.

I once kept the car at 35% at the airport for a week. No sentry but I checked it online periodically after a week it was 33%.

I regularly park for one week at the time most often with low SOC. One week on the model 3 P costed 1% in general and three weeks for a trip to US costed 2%.

My 23 MSP uses around the same amount per day, 0.1 kWh or so or 0.7% for one week.
Both cars, when sleeping except the ~1/day wake up to charge the LV batt uses around 4W in average.

 

[Quickst]

He states to use 30%

We need to understand that audience he is talking to and the subject he is talking about. In the case of the 30% it was an answer to a viewer's question. So - as you say it's a general recommendation that is designed to suit most people. Maybe ideal is not be best word - but in a practical sense its a good number because it gives people a simple answer rather than a detailed scientific answer which most people are not interested.

For other battery talks, he does not actually discuss calendar or cyclic aging per se particularly- he talks about very specific results from research that he is involved in - such as research into depth of discharge and anode microcracking

One week on the model 3 P costed 1%

Mine used up 2% because I checked on the car periodically and turned on sentry periodically

 

[Quickst]

No, that is not right. Your building the case on that 30% is the best SOC, which it clearly is not.

No I am not building a case that 30% is the best SoC. I was referring to the difficulty in using 30% as a target max SoC limit. Below 50% in a Tesla, any SoC setting has to be manually done. For me 30% is a good number except that I need to manually keep at below 50%. Most people don't bother and just leave it at 50%.

The reality is that most people want an easy rule of thumb for managing nickel based battery SoC
Mine is:
20-30% + amount for daily driving or 50%
20-30% if parking more than a week. Add extra to get to charger if required

 

[Geir]

Actually, I think he does’nt state that.

He states to use 30%. That recommendation would probably be because he makes a judgement based on compromises, one being afraid of telling people to leave the cars with too low SOC so they do not start afterwards.

If he actually states that 30% is the SOC causing the lowest degradation he clearly is wrong when we look at all existing research for calendar aging.

He has been stating 70% or 75% begore as the best SOC to use, and in this case he is wromg if we look at what is best for the battery itself. He probably made a judgement with compromises from a tual range in the car etc.

In general I would state that Jeff Dahn either is very wrong in he’s research when he talks about cycles as the prominent degrading factor, or he is bad at expressing himself so we understand him like he means it.
Otherwise he would be not agreeing with the results from very very many research tests/reports.

I urge anyone that look into lithium battery tech not to rely on a single source. That of course includes me as a single source
Read several research reports.

If you find a disagreement, some of the reports are wrong (there is reports coming to strange conclusions but mist often looking at the test data itself it almost always matches the other testdata.


Jeff more or less always use terms hard to understand for the generic viewer and seen here is that people often did get what Jeff stated wrong.
Also, it would be more impressing if the statements matched the resesrch results.

Here is a few calendar aging tests.
There litterally is 100 showing the same thing and there is no tests that shows a increase below 30%.
These are all real tests some of them performed on real Tesla cells.
(There is many many more, but as they all show very similar results, we should if anything instead try to find several tests that would support that 30% is the best SOC from a calendar aging view.
(First we need to understand that a stTed value from for example Jeff might not be the SOC with the lowest calendar aging/degradation but a compromise that always will have the anser related to the input to the compromize and the weighing of the imputs.
One compromixe I could do would for example to advise my freiwnd/collegue about how to charge hea Tesla in the cold winter we have, knowing tje 200km he drives never safely can be driven to work with less than 100%. So the afvice is to charge to 100%.

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No, that is not right. Your building the case on that 30% is the best SOC, which it clearly is not. It is a good number bit the calendar aging teduces down to 0% (the true 0%, way below 0% on our screen).
BTW, if you think 30% is the best, it will be 27% displayed SOC (26.85% actually).

But it is not, so if you park with 30% or 27% and the car drains 0.1% per day it will be good as the SOC reduces all the time.
30% will be good for around 150-200 days or so.
A better thing would be to leave it at 10% or so, as long as the car do not stand for longer than 10 weeks or so.

I regularly park for one week at the time most often with low SOC. One week on the model 3 P costed 1% in general and three weeks for a trip to US costed 2%.

My 23 MSP uses around the same amount per day, 0.1 kWh or so or 0.7% for one week.
Both cars, when sleeping except the ~1/day wake up to charge the LV batt uses around 4W in average.

Can it be said in this way:
Always bee plugged and set the limit to 50/55/60% (according to chemistry). There is nothing to be gained by manually trying to achieve 20 or 30 SOC. ? Or?

 

[Quickst]

There is nothing to be gained by manually trying to achieve 20 or 30 SOC. ? Or?

Maybe, maybe not.

In cold temps (Canadian/scandinavian winters) the sleeping SoC matters a lot less than in hot weather.

In Sydney Australia winter, temps don't drop below 5C. The battery pack in the morning after sleeping overnight typically sits about 15C in unheated garage. Subzero is extremely rare. So maybe it matters more/less depending on climate and geographical area.

Easier to leave max charging limit at 50% compared to below 50% because there is no autolimit setting for SoC below 50%.

For me I'm happy to manually micromanage SoC below 50%

 

[AAKEE]

Can it be said in this way:
Always bee plugged and set the limit to 50/55/60% (according to chemistry). There is nothing to be gained by manually trying to achieve 20 or 30 SOC. ? Or?

Nothing to gain is not really completely true. But the possible difference is so small you might never see the difference.

I have my mantra that I often use:

1) Do not charge more than you need (to the next charge).

2) Charge often (reduces the need in the line above, and reduces the size of the cycles).

3) Charge late so the charge is done shortly before the drive. Reduces the time with high SOC and reduces average SOC)

+ additional info that there is no danger or bad things with low SOC down to 0% so the regime down to that can safely be used and just keep enough to avoid range anxiety and that 100% is not dangerous either so 100% can be used when needed.
+ info about the degradation is cut in half at times when SOC is 55/60/70 or below depending on the chemistry. Keeping the SOC at or below will r duce the degradation by 50% or more.

 

[Geir]

Nothing to gain is not really completely true. But the possible difference is so small you might never see the difference.

I have my mantra that I often use:

Thanks!
But what is then the advantage of always being connected as opposed to keeping even lower SOC? (Around 30%)

 

[E90alex]

Convenience

 

[AAKEE]

Thanks!
But what is then the advantage of always being connected as opposed to keeping even lower SOC? (Around 30%)

As keeping 30% will not give very much range but anyway not a noticable reduction in degradation, 50-55% will give the optimum balance between more or less the lowest degradation.
In my case there is Supercharhers within 50-55% SOC range in all four main roads leaving where I live, so 50-55% is sufficient if I even would start a drive around the world in any direction.

When I park the car at low SOC for a week or so at work or being om vacation It is because I know low SOC is good, and I also know 50-55% might be very close to as good as 5, 10 or 15 or 20%. So when I do this I know it wouldnt be noticable if I left it at 55%. It is more of a principle than actual gain.
Leaving it not connected ensures a spike in the electric net from thunderstorms will not reach into the car.

If you always connect you actually follow Teslas advices. You can do 50 or 55% daily and that is within Teslas advice.
I always have the car connected when at home, but use the scheduled charging that starts early in the morning, like 4 AM or so.

 

[Resist]

So leaving it unplugged if you know you won't drive the car for a week or two, is a good thing. I think I will start doing this because I don't drive my Tesla daily, sometimes not even for weeks. But I wish Tesla would change the app it would allow a low end charge like 20 or 30%, instead of 50%.

What if you put your car in storage for say the winter, because you have others vehicles for the snow driving, what percentage would be best to keep it at?

 

[holmgang]

This thread is like if the hypermiling communities all discovered electric cars

 

[Geir]

As keeping 30% will not give very much range but anyway not a noticable reduction in degradation, 50-55% will give the optimum balance between more or less the lowest degradation.
In my case there is Supercharhers within 50-55% SOC range in all four main roads leaving where I live, so 50-55% is sufficient if I even would start a drive around the world in any direction.

When I park the car at low SOC for a week or so at work or being om vacation It is because I know low SOC is good, and I also know 50-55% might be very close to as good as 5, 10 or 15 or 20%. So when I do this I know it wouldnt be noticable if I left it at 55%. It is more of a principle than actual gain.
Leaving it not connected ensures a spike in the electric net from thunderstorms will not reach into the car.

If you always connect you actually follow Teslas advices. You can do 50 or 55% daily and that is within Teslas advice.
I always have the car connected when at home, but use the scheduled charging that starts early in the morning, like 4 AM or so.

If you normally leave it connected, are there any other advantages if you do so? Cooling, warming , batteryconditionering ………?

 

[AAKEE]

If you normally leave it connected, are there any other advantages if you do so? Cooling, warming , batteryconditionering ………?

No.

The battery is more or never cooled or heated.

In my climate (- as low as -41C last winter), the car did not heat the battery until charging was activated.
The same has been valid for my M3P as well. The car never heats the battery unless a precondition for a drive or charging.
In my climate, up to +30C, the car never cools the battery when parked.

Always connected with a scheduled charge, I always have 55% the next day.

You cold use charging when needed instead of daily, like charging when the SOC is low and chsrging needed for the next day (might be charging only each three days or so then).
But the increased cycle size probably even out the possible gain by using lower SOC so you probably end up with about the same degradation but much less avsilable range.

I also find it a good idea to recommend charging daily, for the non believers.
Tesla states to connect always so by doing this you follow Teslas advice to 100%, even with the charge setting at 50 or 55%.

 

[E90alex]

If you normally leave it connected, are there any other advantages if you do so? Cooling, warming , batteryconditionering ………?

No. Just convenience. The car won’t do anything to the battery just sitting there unless it’s actively charging or you turn on the climate.

If plugged in, it can top up as needed if it drains below a certain amount and eliminate the possibility of some unforeseen phantom/vampire drain depleting the battery. And you can initiate charging anywhere in the world eg if you’re retuning from a trip and need the car to be at a certain % by the time you get home.

 

[Rocky_H]

In my climate (- as low as -41C last winter), the car did not heat the battery until charging was activated.
The same has been valid for my M3P as well. The car never heats the battery unless a precondition for a drive or charging.
In my climate, up to +30C, the car never cools the battery when parked.

I'm going to preface this to say I don't know if the newer cars still do this or not, but my old 2014 will do some active battery cooling when it is very very hot. It will allow a bit higher temperature when it's not plugged in, because it doesn't want to drain range if not fully necessary. But when it gets plugged in, it has the external energy available, so it uses a better temperature threshold. That's a lot higher than 30 degrees C though. It's more like when it's over 40-some degrees C.

 

[Quickst]

So leaving it unplugged if you know you won't drive the car for a week or two, is a good thing

Yes - the car will not see electrical spikes (if any).
No - the car will not maintain battery SoC if you set the auto limit to 50% or more. There will be an extremely slow discharge if you let it sleep and don't operate sentry, or discharge will be higher if you use sentry.

ABC = always be charging. ABC means you can keep SoC low.

What if you put your car in storage for say the winter, because you have others vehicles for the snow driving, what percentage would be best to keep it at

In summer Start with 30% + plus whatever margin you need to get to a reliable commercial charger if your house power is interrupted. In subzero Celsius winters like in Canada, Chicago or Scandinavia where the temp is subzero all day and all night, I don't think it matters what the % is but start with 50%. A frozen battery I think has zero degradation but needs to be warmed up before the reactions can produce electricity. If a severe winter storm is predicted, I would charge higher even 60-70% or even higher in case the grid is also interrupted and commercial DC chargers might also be knocked out.

My winters in Sydney hardly even sees temps below 3-5C at night at +15C during day

If you normally leave it connected, are there any other advantages if you do so?

If you set the limit at 50%? and above, the car will maintain the battery SoC at whatever you set it at. = "set and forget "

Above Just my philosophy. Some based on reading some research papers but obviously not as much as @AAKEE

 

[AAKEE]

I'm going to preface this to say I don't know if the newer cars still do this or not, but my old 2014 will do some active battery cooling when it is very very hot.

I never had a ”old one” but have read about it. Some people states pumps are running above some SOC numbers regardless of the ambient temp on the old ones.


For the newer types, like 3/Y and new S I am pretty sure what happens and not.

For example, when the car is sleeping the HV battery is disconnected with the contactors and the HV batt can not deliver any energy. The LV bat do not contain energy enough to heat anything.

So [Sleep] is a proof of that no battery heating (or cooling) is happening.

And cell temp logs (or visual checks) that shows the battery temp go close to the ambient also is a proof of this.

Also, logs about energy on board shows the same. I know my cars have been sleeping all the time when parked without Sentry except for a very short moment either once a day or every other day or so, this is the car waking up to charge the LV-bat.

Looks like this (sleep only):


Or this (charging the LV-bat):


This was me activating (slow) charging from a wall outlet to heat the battery when the cell temp reached -20C (ambient was -40- -41C this day).
Having the car connected did not wake it up if charging was not activated. So no battery heating even at -40C by the car itself.

 

[boulder.dude]

Q about calendar aging — if person A charges to 80% and person B charges to 50%, then person A’d battery degradation will be faster in the first few years.

Will their total degradation eventually almost converge after say 5-10 years? Or will person A’s battery always be significantly (more than 2% difference) more degraded than person B’s battery?

 

[AAKEE]

Q about calendar aging — if person A charges to 80% and person B charges to 50%, then person A’d battery degradation will be faster in the first few years.

Will their total degradation eventually almost converge after say 5-10 years? Or will person A’s battery always be significantly (more than 2% difference) more degraded than person B’s battery?

Person A will have the double total degradation over time. It will always have a doubled rate compared to person A.

Cyclic degradation is very low (compared to calendar aging) and it is also lower at low SOC.

At the end of a bad day ( after 10 or more years) person A’s battery might start to malfunction because of high degradation for example with some cells getting high internal resistance and rendering too much imbalance in a pack.
Person B’s pack still is “young” compared to person A’s pack.