Long Term Battery Costs, Fears, and Serviceability

[AAKEE]

Hi AAKEE....does the opposite happen ?...in summer when you put on the air conditioner, does it make the battery hotter ?

In general I would say no.

A heat pump moves heat.
The octovalve gives the possibility to select the heat source and also the destination of the heat.
Sources can be outside air, the battery, motors/drivetrain and the cabin. These can also be destinations.

If navigating to a supercharger with the need to precondition and the cabin needs AC, the heat from the cabin will most probably be sent to the battery. (But the most part of the heat to the battery will probably come from outside air).

In other cases the cabin heat will be heat exchanged to outside air.

 

[Bouba]

In general I would say no.

A heat pump moves heat.
The octovalve gives the possibility to select the heat source and also the destination of the heat.
Sources can be outside air, the battery, motors/drivetrain and the cabin. These can also be destinations.

If navigating to a supercharger with the need to precondition and the cabin needs AC, the heat from the cabin will most probably be sent to the battery. (But the most part of the heat to the battery will probably come from outside air).

In other cases the cabin heat will be heat exchanged to outside air.

Thank you for that

 

[DownshiftDre]

Hi AAKEE....does the opposite happen ?...in summer when you put on the air conditioner, does it make the battery hotter ?

Living in the desert in the summer, I can comment on this as I’ve watched thermal management temps closely.

The AC takes the heat from the cabin and dumps it into the refrigerant which then dumps that heat into the coolant before dumped to outside air. This is the same coolant that circulates around the battery. So the battery gets heated while being part of that cascading.

So the answer to your question is a yes. Given a side by side comparison with 2 Model 3/Y in the same hot temperature environment with one having AC cooling ON and the other having AC cooling OFF, the car with AC ON will have a hotter battery due to the heat from cabin being rejected into the coolant loops.

If the Model 3/Y had an actual air cooled AC condenser, it would be able to dump straight from refrigerant to outside air, but since it is a cascading system (liquid cooled condenser), it needs to dump from refrigerant to coolant first then outside air. I believe the Model S/X has a seperate air cooled AC condenser (like normal ICE cars) to dump from cabin straight to air.

 

[AAKEE]

The octovalve can decide where the heat goes. In this picture of the Y, the heat goes to the radiator.
The battery pack coolant can have it’s pwn setting.

With the Octovalve in pos.1 the heat is dumped to ambient.

 

[AAKEE]

We had a warm week.

Today I drove to my parents, 82km single way. Car was in the sun all day, around 25C.

The cell temp was 36-37C after the day, and did rise to 40C during the drive home.

I was too lazy to actually check the different temperatures (which males it possible to detect any heating/cooling by seeing the inlet and outlet temps.

But after the cell temp max reached 40C it stayed there for tve reminder of the drive home.
As we know the passive cooling target is 40C we can be assured that the car was passively cooling the battery during this time.
In the picture in the last post we can see that pos.1 allows for simultaniously cooling the cabin and cooling the battery in that octovalve position.

 

[DownshiftDre]

The octovalve can decide where the heat goes. In this picture of the Y, the heat goes to the radiator.
The battery pack coolant can have it’s pwn setting.

View attachment 1052959


View attachment 1052966

With the Octovalve in pos.1 the heat is dumped to ambient.

Yes the heat is dumped to ambient but check the arrow thickness. The heat is still cabin to refrigerant to coolant to air (through front radiator). It doesn’t stay in this mode for long as the decoupled battery loop heats up as well without the cooling (valve to chiller is closed) so system will eventually leave this mode and go into the series mode where powertrain and battery loops become tied together into one loop. And now as the heat dumps into the coolant the battery heats up extra too.

Hence why I wish (because I use AC in extreme heat) there was a seperate AC refrigerant condenser loop to route heat straight from cabin to refrigerant to outside air…like all ICE cars.

Still a very optimized system for the goals it has but lots of opportunity for performance improvements where there were some compromises made in the final architecture (cost, complexity, weight, volume, part count, etc).

 

[QtownTaxiGreg]

The octovalve can decide where the heat goes. In this picture of the Y, the heat goes to the radiator.
The battery pack coolant can have it’s pwn setting.

View attachment 1052959


View attachment 1052966

With the Octovalve in pos.1 the heat is dumped to ambient.

Check if I understand please.

A/C pump is sending very hot extra high pressure refrigerant via heat exchanger with liquid motor coolant.

A/C retains enough pressure to evaporate in the Cabin evaporator cooling the cabin air.

The even hotter engine coolant goes through the radiator and heat goes ambient enough that it cools motor.

What a balancing act!

The yellow circuit is a mystery. "Chiller"?

 

[DownshiftDre]

Check if I understand please.

A/C pump is sending very hot extra high pressure refrigerant via heat exchanger with liquid motor coolant.

A/C retains enough pressure to evaporate in the Cabin evaporator cooling the cabin air.

The even hotter engine coolant goes through the radiator and heat goes ambient enough that it cools motor.

What a balancing act!

The yellow circuit is a mystery. "Chiller"?

The chiller is active in mainly battery cooling modes where the battery is in its own coolant loop. The chiller is a refrigerant coolant heat exchanger. So Cold Refrigerant is routed through the chiller and pulls heat out of the battery coolant loop.

Will add, It is also active is battery heating modes as well.

 

[Dr. J]

What is then the + to have the car plugged in when you don’t need the higher state of charge? When not charging, which adventages to have it plugged?

The + to staying plugged in is keeping your 12-volt battery properly charged so the car will start.

 

[cwerdna]

Summer is coming....and now I am starting to worry...because time and heat are killing our batteries...as shown in AAKEE’s graph..



Especially as I have the NMC ......they are the most susceptible to heat.
But this is my question.....the graph was made using battery cells kept at a continuous state of charge and continuous heat (I assume)....so if a car is kept parked in the sun but not all the time....a day here, a week there, 45 minutes, etc etc....is the damage done by the accumulated time equal to the continuous time on the graph ?

I've been too busy to keep up with this thread but I'd been wondering where the various graphs were coming from. From a quick Google search from some of the keywords in the above, Iooks like the above comes from page 7 (A1877) of Radware Bot Manager Captcha. Radware Bot Manager Captcha points to the PDF. (Argh, the software expands the link to "Radware Bot Manager Captcha".)

I'm not sure if the links were posted already but I didn't notice them. Perhaps I searched for the wrong user/thing.

For the others posting screenshots of graphs, would be helpful to point to the source.

(Side note: On TiVo Community, we have the term Urban Dictionary: smeek, named for the poster jsmeeker.)

 

[AAKEE]

I've been too busy to keep up with this thread but I'd been wondering where the various graphs were coming from.

Here!

 

[cwerdna]

Here!

Is that the right reference? It leads to a paper titled "Octovalve Thermal Management Control for Electric Vehicle". From skimming, I didn't see any battery degradation-related graphs.

 

[AAKEE]

Is that the right reference? It leads to a paper titled "Octovalve Thermal Management Control for Electric Vehicle". From skimming, I didn't see any battery degradation-related graphs.

Ahh, my fault. Was so into the heat pump discussion.

This one is the source of that picture.

 

[gottagofast]

I noticed I’ve been losing estimated range ever since I started daily charging to 50-55% and arriving home with 23-30%

2 months ago I was showing 145 miles of range at 50% charge, then it was 144 miles, now today it’s 143 miles, this wasn’t happening when I was charging to 70-80%

Car hasn’t been charged to 100% in a year, I might try it and see what happens and use my 100% charge over 3 days

Reading various comments on Reddit there seems to be a trend of people with low degradation charge their cars to 100% atleast a few times per year mostly for trips, but I haven’t been on any trips to charge to 100%, people that never charge to 100% seem to have more degradation

 

[Bouba]

I noticed I’ve been losing estimated range ever since I started daily charging to 50-55% and arriving home with 23-30%

2 months ago I was showing 145 miles of range at 50% charge, then it was 144 miles, now today it’s 143 miles, this wasn’t happening when I was charging to 70-80%

Car hasn’t been charged to 100% in a year, I might try it and see what happens and use my 100% charge over 3 days

Reading various comments on Reddit there seems to be a trend of people with low degradation charge their cars to 100% atleast a few times per year mostly for trips, but I haven’t been on any trips to charge to 100%, people that never charge to 100% seem to have more degradation

If you think the range will come back by charging to 100%...then you haven’t actually lost any range....just the battery management program can’t get a good estimate on the regular charge you use

 

[gottagofast]

If you think the range will come back by charging to 100%...then you haven’t actually lost any range....just the battery management program can’t get a good estimate on the regular charge you use

I see comments sometimes like I never let my car go below 40% or above 70% and I’ve lost 13% range

Then another person says I’ve charged to 100% many times and I’ve only lost 5%

Seems to be some conflicting between studies and real world results

 

[Bouba]

I see comments sometimes like I never let my car go below 40% or above 70% and I’ve lost 13% range

Then another person says I’ve charged to 100% many times and I’ve only lost 5%

Seems to be some conflicting between studies and real world results

But you also see that people can recalibrate their batteries.....if you believe AAKEE (and I do)...then the science tells us that low state of charge in a cold environment is best

 

[gottagofast]

But you also see that people can recalibrate their batteries.....if you believe AAKEE (and I do)...then the science tells us that low state of charge in a cold environment is best

So people that charge to 100% a few times per year for trips are kinda recalibrating their battery on accident instead of on purpose

While the person that never charges to 100% has never calibrated their battery and it looks like they have a lot of range loss

I don’t see a person with 13% loss deciding to charge to 100% one day would gain back 8% of their battery though can you gain back that much just from calibration?

 

[Bouba]

So people that charge to 100% a few times per year for trips are kinda recalibrating their battery on accident instead of on purpose

While the person that never charges to 100% has never calibrated their battery and it looks like they have a lot of range loss

I don’t see a person with 13% loss deciding to charge to 100% one day would gain back 8% of their battery though can you gain back that much just from calibration?

I don’t know....there are millions of car batteries out there...we hear from a few happy or disgruntled people on the internet...what should we make of it ?....the science tells us that a chemical reaction occurs that is repeatable and quantifiable....outliers don’t tell us that much useful (unless enough occur to be statistically relevant).
I’m no different to you...I want to follow the science but I also want to know what someone else did that made his battery last forever. I also want to buy the winning lottery ticket but I am almost certain I won’t...but I still part with my money.

 

[AAKEE]

I noticed I’ve been losing estimated range ever since I started daily charging to 50-55% and arriving home with 23-30%

While I havent seen any tendencies to this, I can asure that you do not loose real range.

It might be possible that the BMS get off track, and show less range but the battery itself lives better than ever at these low SOC ranges.

I always need longer drives at least ones a month so I havent stayed low for that long.
I might have been ~ 1.5 months at 55% and below without any higher charges but these have never showed lower range on my M3P. It has regained range by being low long time.
My MSP might “loose” a half percent/0.5 kWh after one month low. (But it always regains 0.5-1kWh that was lost from high SOC / supercharging / larger cycles.
This “recovery is probably real capacity recovered, and the possible loss after ~ 1 month would problably be the BMS getting slightly off.

2 months ago I was showing 145 miles of range at 50% charge, then it was 144 miles, now today it’s 143 miles, this wasn’t happening when I was charging to 70-80%

Car hasn’t been charged to 100% in a year, I might try it and see what happens and use my 100% charge over 3 days

Reading various comments on Reddit there seems to be a trend of people with low degradation charge their cars to 100% atleast a few times per year mostly for trips, but I haven’t been on any trips to charge to 100%, people that never charge to 100% seem to have more degradation

I am quite sure you have less degradation from this year at 55% and below than you would have using the usual 80%.

We know that battery degradation is very predictable and does happen in a controlled rate from factors we understand.
Low SOC will preserve the battery.

You could perform a BMS calib if you like, but that only will restore displayed range, not the real drivable range. Guess you know how to perform a BMS calib?
No sentry, no perping in the app meanwhile.
The car needs to sleep at different SOC to measure the open circuit voltage (no load on the battery goves the perfect SOC reading).
The BMS would need to see high SOC and low SOC. You could do 90-100% SOC and let it sleep for three hours or so, and also single digit SOC for three hours or so as well. Several times might be needed and it could be good with sleep at 70-80% as well. (This means inducing slight extra degradation to reach your goal of a BMS calib)