Weird message came up suggesting I change the charge limit to 71%?

[AAKEE]

Aakee, I’m a little confused by your graphs and conclusions. According to the first graph, it looks like keeping the battery below 55% helps with calendar aging.

Yes, it does.

But the second graph seems to show that cycling 50% to 100% kept the most battery health when compared to 0% to 50%.

We need to understand the magnitudes.
The calendar aging will have a 10x impact compared to the cyclic aging during the first ~ 5-8 years of the battery life.

For the 50-100% and 0-50%, we see a degradation in the worst case (50-0%) that equals about 1.25% cyclic wear in average until 25% is lost (which would take ~ 20years of average driving).
No one will drive like that (0% displayed is ~4.5% real SOC).
The 100-50% would loose about 25% after ~ 3000 FCE cycles so ~ about 0.45% each year.

Calendar aging will degrade the battery (in an average climat) about 5.5% in calendar aging the firat year if high SOC is used (above 55% mainly), se the chart (there is a similar for model 3 cells).
After 4 years we have lost 11% in calendar aging and after 16 years 22%
If we instead ise low SOC, we cut the calendar aging in haft, getting 2.75% first year and 5.5% after four years, and 11% after 16 years.
The first eight years will ”cost” ~8% calendar aging if low SOC is used, plus another 1.25% for cyclic aging each year= 18% total degradation.

If high SOC is used we double the calendar aging to ~16%, and the cyclic aging will be ~ 3.6% so in total ~20%.

IRL, the cycles will not end up with 50-0% in the car, and this research was performed with 1C load, which is equal to 75-80kW in the 3/Y.
We can see from other research (using nore representative power that low SOC is rather good. Part of this researchs result was due to the high current and charge discharge to the end point.

The 3rd graph shows that cycling 5% to 15% did much worse than cycling 85% to 95%, which goes against the conclusion that lowest SOC is best above all.

Again, the magnitude most be noticed and considered.
5-15% equals 0-10% displayed SOC.
Still, being the worst case scenario the cells lost ~17-18% after 3000 FCE. This equals 3000 x 400 km driving range, so 1.200.000
The 1.2 million km is sufficient for ~60 years of average driving. So 17-18% /60 years = 0.29% in average for one year.

Compared to the 2.75% or 5.5% calendar aging the first year, 0.29% calendar aging each year is very low.

Maybe I am interpreting the graphs wrong, but according to graphs 2 and 3 it looks like cycling at the high range is better than a low range, but that goes against the first graph and the conclusion that you want to keep the SOC low to prevent calender aging.

I guess you understand that cyclic aging is only a fraction of the total and that you should not look at cyclic aging mainly when

For reference, I typically use 30% during my commute. I’m trying to figure out if I should:

Cycle 25% to 55% (keeps battery below that 55% “cliff” in graph one)

Cycle 35% to 65% (keeps median SOC around 50%, which seems to do best in graph 3, but goes over the 55% “cliff” that also seems to cause a penalty in graph 3 in the 55-65 result vs the 25-35 result).

Regardless, I will definitely start using the departure scheduling.

The middle graph with cyclic aging at 100-50% and 50-0% use the extremes, and are not really representative, as the cyclic charge and discharge current are much higher than for real driving/charging.

Each 0.1V is about 10% SOC.
4.2V = 100%
2.5V = 0% true SOC.
3.2V = close to 0% displayed.

You can see that small cycles are better and that lower SOC also is better for the cyclic wear

You can see that we have the lowest degradation per cycle between 35-55%.
And that 25-35% is comparable with 55-65,65-75,75-85 and 85-95%.

So, even if any of this curves actually are showing degradation small enough to be disregarded, the best option for calendar aging, to charge to 55% any time thats sufficient will also cause very little cyclic aging

You should only consider calendar aging for normal average driving, as cyclic wear is negligible. And if you still wish to consider it, the best SOC range matches the max 55% charging level.

This is how to think:

- Do not charge more than you need until the next charge.
- Charge often (reduces the need above and reduces cycle size)
-charge late (reduces calendar aging, specially the times you need to charge higher than 55%.

 

[RJUK]

Sorry, a few more questions, if I may?

1.) Do we know what affect SOC has on the car's ultimate power output?

I previously read that power drops off quickly below 80%. Is that correct? For me, that's my only reason for charging above 55%. It seems silly to buy the Performance version, then run it entirely at an SOC that reduces the power output.

2.) Presumably, charging to (to keep things simple) 100%, then using 10% Monday, 10% Tuesday, 10% Wednesday, 10% Thursday and 10% Friday, then recharging, would count as a single "cycle"?

And presumably it would be marginally better for the battery to be charged to 100% each day, then use 10% then charge again to 100% daily? But better still to charge to just 55% each day and repeat?

3.) Lastly, you mention that most of the calendar ageing happens in the first 5 - 8 years? Is that because the battery somehow "resists" ageing better after that period? Or is it more that the battery starts resisting ageing after it has degraded a certain amount (which is usually reached after 5 - 8 years)?

What I mean by this is, is if you run the battery at a very low SOC and top it up a tiny bit after every trip for the first 5 - 8 years, achieving the minimum possible degradation over that period, will the battery at that point have "built up resistance" to ageing and then be able to resist degradation at higher SOCs better, or is it the degradation itself that helps it resist further degradation down the line?

So if we compared 2 batteries at 10 years old with the same mileage, one that has been really looked after for 5 years, then used "normally" and another that has been used "normally" the whole time, would the first one have caught up with the other one's degradation, or will using it carefully for 5 years from the start "lock in" that improvement for the rest of the battery's life?

 

[AAKEE]

Sorry, a few more questions, if I may?

1.) Do we know what affect SOC has on the car's ultimate power output?

The possible power output from a battery is depending on battery voltage and internal resistance.
High SOC = high voltage - good
High battery temp = low internal resistance - good.

Charging late with high power (max AC / 11kW) as I mostly do will make the battery deliver better power.

I previously read that power drops off quickly below 80%.

It is a combo of SOC and battery temp.
Supercharge to 60-70% and it will be quite quick.

Is that correct? For me, that's my only reason for charging above 55%.

When I had my M3P, I charged higher when i needed more power.

There’s also a thing about internal resistance so if you keep your M3P at high SOC or around much, the battery will increase the internal resistance faster. This means it will probably deliver less power in the end.

It seems silly to buy the Performance version, then run it entirely at an SOC that reduces the power output.

2.) Presumably, charging to (to keep things simple) 100%, then using 10% Monday, 10% Tuesday, 10% Wednesday, 10% Thursday and 10% Friday, then recharging, would count as a single "cycle"?

Yes, one cycle with 50% depth of discharge.

And presumably it would be marginally better for the battery to be charged to 100% each day, then use 10% then charge again to 100% daily? But better still to charge to just 55% each day and repeat?

If you use high soc the calendar aging will be higher as you keep the battery at high SOC.
55% or below cuts the calendar aging in half.

3.) Lastly, you mention that most of the calendar ageing happens in the first 5 - 8 years? Is that because the battery somehow "resists" ageing better after that period?

Yes, the solid electrolye interphase that grows and steals cyclable lithium also protects the battery.

Or is it more that the battery starts resisting ageing after it has degraded a certain amount (which is usually reached after 5 - 8 years)?

The calendar aging reduces its rate with the square root of the time.
To double the calendar aging from the first year, you need three more years (in total 4 years.)
To double the degradation of four years you need 12 more years (16 in total).

What I mean by this is, is if you run the battery at a very low SOC and top it up a tiny bit after every trip for the first 5 - 8 years, achieving the minimum possible degradation over that period, will the battery at that point have "built up resistance" to ageing and then be able to resist degradation at higher SOCs better, or is it the degradation itself that helps it resist further degradation down the line?

No, most probably it will be the amount of SEI build up that decides this. So the ”protection” is dependant on the tine/degradationt

So if we compared 2 batteries at 10 years old with the same mileage, one that has been really looked after for 5 years, then used "normally" and another that has been used "normally" the whole time, would the first one have caught up with the other one's degradation, or will using it carefully for 5 years from the start "lock in" that improvement for the rest of the battery's life?

It probably catches up, or partly does.
I havent seen any tests on this.
I am waiting for data from my m3P
The new owner use high SOC.

 

[geofox784]

Thanks for the response AAKEE. So it sounds like in my case, I should charge to 55% which will leave me 20%-25%, then I will use departure scheduled charging to have it reach 55% right before the next day.

Other than decreased performance, is there anything damaging about running the battery to a low SOC like 20%, or even lower? I see several discussions elsewhere that seem to mention you should also avoid the 0% to 20% SOC just like you should avoid 80% to 100%, but I haven't seen any explanation as to what exactly is causing damage at a low SOC.

 

[AAKEE]

Thanks for the response AAKEE. So it sounds like in my case, I should charge to 55% which will leave me 20%-25%, then I will use departure scheduled charging to have it reach 55% right before the next day.

Other than decreased performance, is there anything damaging about running the battery to a low SOC like 20%, or even lower? I see several discussions elsewhere that seem to mention you should also avoid the 0% to 20% SOC just like you should avoid 80% to 100%, but I haven't seen any explanation as to what exactly is causing damage at a low SOC.

No, theres no damage coming with low SOC. That is a myth.
Just as the myth that 100% should be very bad. It is not.

As for the myths, theres is no research supporting the myths (that’s why I call them myths).
If you actively search for real facts for these myths, you will not find anything.


The batteri is happy at low SOC.

It can be worth noticing that the calendar aging curve is rather flat between ~30-55% in most research, and below 30% there is a reduction but it will not make a big difference.
So the big change is to have the battery at or below 55%. Sometimes the discussion arise about measures to try to stay very low SOC, but the gain isnt worth the pain.

I selected 55% as the standard daily, as it offers 10% more range than the lowest setting (50%) but still have the same degradation in total. The 5% SOC from 50-55% is free in that perspective.

I still use 55% on the days it is just precise enough, and I park happily with single digit SOC numbers. (But not stupidly risking to be stranded of course).
My work is 240km away, and the car is parked for one week at the time, I mostly plan to arrive at ~10-15% and this is to have a margin for rerouting for accidents etc. So it mostly is parked atound those numbers.

 

[RJUK]

Thanks again Aakee.

I presume these behaviours apply also to the lithium batteries in other items such as eBikes/mobile phones/laptops? (Give or take?)

The reason I ask is because I always aim to charge my phone to 80% as well, to try to limit degradation.

I also have an ebike and don't fully charge that, either, but I had been bringing the battery inside in winter so it wasn't subject to the extreme cold... But I'm wondering if that's the right thing to do, or if leaving it in the coldest possible temperatures is better for it?

Again there seem to be a lot of misconceptions around batteries and temperature. I had previously read that they wet kept at cooler temperatures for storage, but then saw things suggesting that batteries don't like the cold and it was detrimental to them.

Would it be correct to say that keeping a lithium battery at a low temperature is good for reducing degradation, but is poor for charging it quickly and also poor for extracting energy from it quickly (as in hard acceleration in a car)?

Also, is there a point at which it becomes "too cold" for the battery and actually starts damaging it?

 

[AAKEE]

Thanks again Aakee.

I presume these behaviours apply also to the lithium batteries in other items such as eBikes/mobile phones/laptops? (Give or take?)

The reason I ask is because I always aim to charge my phone to 80% as well, to try to limit degradation.

I tried ~50% until I needed more each day.
Smaller cycles is good so charge when driving the car and so on.

I also have an ebike and don't fully charge that, either, but I had been bringing the battery inside in winter so it wasn't subject to the extreme cold... But I'm wondering if that's the right thing to do, or if leaving it in the coldest possible temperatures is better for it?

Cold is good. Temperature has the same effect as SOC, so…

Again there seem to be a lot of misconceptions around batteries and temperature. I had previously read that they wet kept at cooler temperatures for storage, but then saw things suggesting that batteries don't like the cold and it was detrimental to them.

If you put a cell in a plastic bag and that bag in the freezer, the air inside the bag contains moisture that will fall out as dropplets when the air cools.

Would it be correct to say that keeping a lithium battery at a low temperature is good for reducing degradation, but is poor for charging it quickly and also poor for extracting energy from it quickly (as in hard acceleration in a car)?

Yup.

Also, is there a point at which it becomes "too cold" for the battery and actually starts damaging it?

At -20C the calendar aging is slow (almost none). I let the pack cool when the car is parked for long outside but I activate charging after -30C or below for 24h, like the manual states.
Ive seen cell temps down to ~18C before activating battery charging/heating.

Tesla states -20C to +60C in the EPA test applications.

 

[RJUK]

OK, here in the UK we never see it that cold where I live, so presumably I would be better off leaving the battery in the garage all year round, as it tends to be the coolest place?

Should I remove it from the bike or is leaving it in there likely OK?

I guess then I should bring it into the house for a while to warm up before initiating a charge? Or is that not necessary either, because the charging itself will warm the battery? I'm still unsure if charging a battery when it's cold is damaging to it, or just slower to charge. The latter isn't an issue for me, but the former would be.

 

[AAKEE]

OK, here in the UK we never see it that cold where I live, so presumably I would be better off leaving the battery in the garage all year round, as it tends to be the coolest place?

Should I remove it from the bike or is leaving it in there likely OK?

In the garage, probably best to renove from bike if easy to ensure the bike do not draw it empty.

I guess then I should bring it into the house for a while to warm up before initiating a charge? Or is that not necessary either, because the charging itself will warm the battery? I'm still unsure if charging a battery when it's cold is damaging to it, or just slower to charge. The latter isn't an issue for me, but the former would be.

Let it warm before charging.

Lithium batteries should not be charged when the cells are sub freezing so best to let it acclimatize to room temp first.

 

[RJUK]

Great stuff, thanks. The bike does draw a small bit of power to keep a GPS security module on it charged, but the model draws very little power, so probably wouldn't draw much over a long time.

I guess I could leave it in there to bring the SOC down and just check it intermittently. It's on around 46% SOC currently and is quite a large battery.