V3 Supercharger, charge speeds in cold weather. Scan My Tesla data

[pt19713]

There's been a lot of talk about less-than-ideal charge speeds at the V3 superchargers in colder climates, so I decided to log the session.

I drove about 90 minutes and arrived at my in-laws house and had lunch, so the car sat idle for 90 minutes. The battery pack was at 64F at the end of the drive, 17% SoC.

I entered the Tesla supercharger location in the NAV to start the pre-conditioning process. Battery pack was at 51F, so a drop of 13F. UI was displaying the snow flake icon, 11% SoC displayed on the UI, 14% displayed in Scan My Tesla app. After about 8 minutes, the snow flake icon disappeared when the battery pack temp reached around 58F. In hindsight, I should've logged the pre-conditioning drive to the supercharger to show all this data. A few random things I've noted: the front stator motor only gets to around 120F during the process, consuming 2 kW. This isn't as effective as preconditioning parked, where the front motor can reach 210F. During the 20 minute drive to the supercharger, the battery pack went from 51F to 68F, which is well below what is needed to see the full speeds at a Level 3 charger. Ideally you want the battery pack to be closer to 100F if you want to see the full charging speeds.

Below is the graph of the charging session. As noted in the title and footers, the ambient temp was 33F, wind 10-15 mph, with gusts up to 25F. I started the charge at 9.8% SoC, ended at 80%, total duration of 33 minutes.

You can see the stator motors quickly heating up and within 2 minutes the front motors were at 219F, the rear motors were at 176F. The battery packs started at 69F, ended at 131F.

In about 90 seconds after plugging in is where I saw the max charge rate of only 157 kW and then tapering off over time, as shown on the graph. I noted where the 20% SoC is on the graph. At that point, the battery packs were only 80F, or around 3.5 minutes into the charge. The battery packs hit the optimal temp of 100F a little after 9 minutes but by then, the SoC was at 35% and the BMS had already started throttling back the charge to 113 kW.

I'll do more logs when it gets warmer out so we can see how these all behave when the packs are already at 90+ F at the start of the charge.

 

[craigery]

Love all this data! For historical purposes, could you also include the software version the car was on at the time of charge? Are you using scan my Tesla to actually log this data as well? I don’t see this functionality in the IOS version of the app.

 

[pt19713]

Love all this data! For historical purposes, could you also include the software version the car was on at the time of charge? Are you using scan my Tesla to actually log this data as well? I don’t see this functionality in the IOS version of the app.

Software was 2020.48.35.5. I'll make sure to note that in the footer for future logs.
Yes, I'm using the Scan My Tesla app for Android, graph is with DatPlot.
IOS is called "Scan My T3sla" since Apple had issues with the creator using "Scan My Tesla" in the Apple Store.

 

[craigery]

Software was 2020.48.35.5. I'll make sure to note that in the footer for future logs.
Yes, I'm using the Scan My Tesla app for Android, graph is with DatPlot.
IOS is called "Scan My T3sla" since Apple had issues with the creator using "Scan My Tesla" in the Apple Store.

I’ve got the app, but I’m not seeing how to log / record the data. I just see realtime data. I know this was an Android first app so perhaps that feature is coming or I’m just not seeing it.

 

[pt19713]

I’ve got the app, but I’m not seeing how to log / record the data. I just see realtime data. I know this was an Android first app so perhaps that feature is coming or I’m just not seeing it.

If you push the red button on the lower right, that'll start the log, as indicated by the blinking light. Push it again to stop the log. Click on the wrench icon on the upper left, select View Logs, then find where your files are stored to transfer them to a computer. I believe this is the same method for iOS but don't quote me on that. There is a Scan My Tesla Facebook group, along with one this thread here:
Scan My Tesla official thread (support, suggestions, discussion, feedback)

On page 2, a user lists an Excel formula to convert the time from milliseconds to seconds, pretty useful.

 

[silverstoned83]

Thanks so much for taking the time to share this data. Consider me subscribed!!

 

[TomServo]

Looks like your results mirror Bjorn's cold weather testing with the new 2021 M3 he's been testing. Unfortunately most new Tesla owners aren't this "tech savvy" and will complain about how slowly their SC sessions are. Maybe Tesla could start including a few "warning" messages informing the owner of these limitations and how to mitigate them with out having to buy "third party" accessories and keep track of all that data while driving.

 

[pt19713]

A simple UI update to show a bar for the battery temp, a section to show where it's ideal (like a gas engine coolant temp gauge), another section to show max charging speed if the battery is in that section, etc.

I understand they dumb it down for the consumer but they do it a bit too much. Even for this charging session, the app wouldn't let me pre-condition via the in-cabin heat because it thought my battery was too low (roughly 14%). If I pre-conditioned and used 3%, I would've arrived at the supercharger with 6% and a much warmer battery that would've been around 85F, not 69F.

 

[TomServo]

A simple UI update to show a bar for the battery temp, a section to show where it's ideal (like a gas engine coolant temp gauge), another section to show max charging speed if the battery is in that section, etc.

I understand they dumb it down for the consumer but they do it a bit too much. Even for this charging session, the app wouldn't let me pre-condition via the in-cabin heat because it thought my battery was too low (roughly 14%). If I pre-conditioned and used 3%, I would've arrived at the supercharger with 6% and a much warmer battery that would've been around 85F, not 69F.

Seems like a simple OTA update, I'd rather they spend their engineering hours doing that than a new "fart" sound.

 

[jcanoe]

A simple UI update to show a bar for the battery temp, a section to show where it's ideal (like a gas engine coolant temp gauge), another section to show max charging speed if the battery is in that section, etc.

I understand they dumb it down for the consumer but they do it a bit too much. Even for this charging session, the app wouldn't let me pre-condition via the in-cabin heat because it thought my battery was too low (roughly 14%). If I pre-conditioned and used 3%, I would've arrived at the supercharger with 6% and a much warmer battery that would've been around 85F, not 69F.

If you navigate to the SC when the Tesla's battery SOC is as it was for this test, less than 20%, would Tesla still warm the battery so that by the time you arrived at the SC (assuming you start out 20 minutes away from the SC) the battery would be in the optimal temperature range for charging at the SC?

 

[pt19713]

If you navigate to the SC when the Tesla's battery SOC is as it was for this test, less than 20%, would Tesla still warm the battery so that by the time you arrived at the SC (assuming you start out 20 minutes away from the SC) the battery would be in the optimal temperature range for charging at the SC?

No, the Tesla NAV pre-conditioning process isn't as aggressive compared to when the car is parked idle. I noted in the original post that the front Stator motor is only consuming 2 kW and I never saw it get above 120-125F during the drive. When the car is parked idle and pre-conditioning, it consumes 3.5 kW and can get the front Stator motor to around 190-200F in the same 15 minute duration. I'm not sure why Tesla limits the front motor at 2 kW during the pre-conditioning while driving. I'm sure there's a good technical reason, I just don't know why.

Based upon what I saw in terms of starting and ending temp, the Tesla supercharger location / pre-conditioning process in temps of 32-33F would take well over 60 minutes to get the battery pack to 85-90F. This is also without the use of any in-cabin heat. If in-cabin heat is used, I don't think the battery packs would get over 75-80F. This is slightly off topic, but whenever I turn the heat on, I see the battery inlet temp of the refrigerant drop by 10-15F within 30 seconds.

 

[jcanoe]

No, the Tesla NAV pre-conditioning process isn't as aggressive compared to when the car is parked idle. I noted in the original post that the front Stator motor is only consuming 2 kW and I never saw it get above 120-125F during the drive. When the car is parked idle and pre-conditioning, it consumes 3.5 kW and can get the front Stator motor to around 190-200F in the same 15 minute duration. I'm not sure why Tesla limits the front motor at 2 kW during the pre-conditioning while driving. I'm sure there's a good technical reason, I just don't know why.

Based upon what I saw in terms of starting and ending temp, the Tesla supercharger location / pre-conditioning process in temps of 32-33F would take well over 60 minutes to get the battery pack to 85-90F. This is also without the use of any in-cabin heat. If in-cabin heat is used, I don't think the battery packs would get over 75-80F. This is slightly off topic, but whenever I turn the heat on, I see the battery inlet temp of the refrigerant drop by 10-15F within 30 seconds.

Thank you for the explanation. I noted where you stated that the front motor only consumed 2kW while driving versus 3.5kW when parked. Is it possible that the software is not correctly distinguishing power consumed by stator heating with power consumed otherwise while driving. The front drive motor does not contribute much if any propulsion while driving at a steady speed. What about the rear drive unit motor; does the rear motor continue to consume 3.5kW for stator heating while driving or is there no way for the monitoring software to separate power used for stator heating from power used for propulsion?

It would appear based in part by your data that when driving from SC to SC in similar cold temperature conditions it may not be possible to achieve optimal battery temperature for the SC charging session because a) the Nav preconditioning does not turn on soon enough, b) cabin heating uses much of the heat being generated preventing the battery from reaching the desired temperature. It would be bad if you have to turn down or turn off the cabin heat for ~45 minutes on the way to a SC so that the battery would be a bit warmer when you started charging.

 

[meh_]

Interesting data. So what would you suggest to get the battery up to temp prior to a SC?

Say I'm home and plan on going to the SC to charge up, am I better off leaving it parked with the climate on for a certain period of time with the SC plugged into the Nav as the destination than just driving there right away?

 

[pt19713]

Thank you for the explanation. I noted where you stated that the front motor only consumed 2kW while driving versus 3.5kW when parked. Is it possible that the software is not correctly distinguishing power consumed by stator heating with power consumed otherwise while driving. The front drive motor does not contribute much if any propulsion while driving at a steady speed. What about the rear drive unit motor; does the rear motor continue to consume 3.5kW for stator heating while driving or is there no way for the monitoring software to separate power used for stator heating from power used for propulsion?

It would appear based in part by your data that when driving from SC to SC in similar cold temperature conditions it may not be possible to achieve optimal battery temperature for the SC charging session because a) the Nav preconditioning does not turn on soon enough, b) cabin heating uses much of the heat being generated preventing the battery from reaching the desired temperature. It would be bad if you have to turn down or turn off the cabin heat for ~45 minutes on the way to a SC so that the battery would be a bit warmer when you started charging.

I can't really say if it's a software issue or by design, but most likely a wide range of factors and only the Tesla software engineers would know. I always wondered why I only saw the front motors pulling 2 kW instead of 3.5 kW during the Tesla SC NAV pre-conditioning. There's probably some technical reason with the front induction motor not being able to generate more heat while in motion. Maybe a mechanical engineer can chime in.

The only way I can see if the rear motors are generating 2 or 3.5 kW is if I'm at a complete stop. I wasn't fully paying attention during the drive there so I can't remember if it was 2 or 3.5 kW. I'll have to test another time (and actually log the drive).

 

[jcanoe]

Interesting data. So what would you suggest to get the battery up to temp prior to a SC?

Say I'm home and plan on going to the SC to charge up, am I better off leaving it parked with the climate on for a certain period of time with the SC plugged into the Nav as the destination than just driving there right away?

I believe that the Nav to SC preconditioning only starts warming the battery while driving. Your only option is to precondition normally before driving, then use the Nav to SC to continue warming the battery.

 

[pt19713]

Interesting data. So what would you suggest to get the battery up to temp prior to a SC?

Say I'm home and plan on going to the SC to charge up, am I better off leaving it parked with the climate on for a certain period of time with the SC plugged into the Nav as the destination than just driving there right away?

Unless you have the harness to plug in and pull the data from the CAN bus, you won't be able to see what the battery temps are.
But yes, ideally you'd pre-condition at home to get the battery to somewhat warmer temps. To get the battery pack from ~ 40F to 80F would take about 20-25 minutes. If you have a HPWC and can charge at 11.7 kW, this process should be able to pull energy from the grid and not the battery. The caveat is if the defrost setting is at HI. This can pull around 12-12.5 kW. I never use the defrost setting on HI but instead set the cabin temp to around 66-67. This will pull 3.5 kW per motor, 7 kW total, plus another 700-800 watts to run the various car accessories. You'll still get around 3.9 to 4.0 kW to the battery while pre-conditioning. If you use a NEMA 14-50 at 32A, this will provide about 7.6 kW, just enough to pull from the grid and a little bit from the battery.

Depending on the battery pack temp and the distance to the supercharger, at least 20 minutes is what I'd recommend if you want faster charging speeds This will get the pack to at least 75-80F and the drive to the supercharge will get that up to 85F. Still not at the 100F ideal temp but this is something we'll have to deal with in colder climates.

 

[meh_]

Unless you have the harness to plug in and pull the data from the CAN bus, you won't be able to see what the battery temps are.
But yes, ideally you'd pre-condition at home to get the battery to somewhat warmer temps. To get the battery pack from ~ 40F to 80F would take about 20-25 minutes. If you have a HPWC and can charge at 11.7 kW, this process should be able to pull energy from the grid and not the battery. The caveat is if the defrost setting is at HI. This can pull around 12-12.5 kW. I never use the defrost setting on HI but instead set the cabin temp to around 66-67. This will pull 3.5 kW per motor, 7 kW total, plus another 700-800 watts to run the various car accessories. You'll still get around 3.9 to 4.0 kW to the battery while pre-conditioning. If you use a NEMA 14-50 at 32A, this will provide about 7.6 kW, just enough to pull from the grid and a little bit from the battery.

Depending on the battery pack temp and the distance to the supercharger, at least 20 minutes is what I'd recommend if you want faster charging speeds This will get the pack to at least 75-80F and the drive to the supercharge will get that up to 85F. Still not at the 100F ideal temp but this is something we'll have to deal with in colder climates.

Gotcha. I use a 14-50 and have a supercharger about 15 min away from me.

If I precondition at home and both the interior and battery temps are 40ish degrees. Will it stop conditioning the battery when it reaches the desired interior temp? Just wondering if it is better to have a higher interior temp or if it would benefit from setting it to 65 or so instead.

 

[pt19713]

Gotcha. I use a 14-50 and have a supercharger about 15 min away from me.

If I precondition at home and both the interior and battery temps are 40ish degrees. Will it stop conditioning the battery when it reaches the desired interior temp? Just wondering if it is better to have a higher interior temp or if it would benefit from setting it to 65 or so instead.

Yes, the BMW will manage the Stator motors and throttle them, if needed, along with various adjustments in the refrigerant flow, fan speeds, etc. If you look at the top part of the graph in my first post, you can see both Stator motors dropping in temp, which I found surprising. For some reason the BMS throttle back the Stator motors and also throttled back the charging speeds. After about 5-6 minutes, the BMS decided to warm up both motors again.

The reason I set my interior cabin temp low is to get the pre-conditioning process started and the BMS will redirect more of the warmer refrigerant to the battery instead of the cabin once the cabin temp is reach. Let me dig up another graph that shows this.

 

[pt19713]

Here's a graph I made a few months ago. Sorry for it not being legible. I had some issues with my snipping tool.
what you're looking at here is the red line, which is the temperature of the refrigerant before it goes into the battery pack. Right around the 2 minute mark, you can see where it spikes up. This is the point where it finished heating the cabin and more of the heat is routed away from the heat pump to the battery pack. Obviously this will occur later if you have the cabin temp set higher (and the cabin starting temp is lower), but it gives you an idea how the Octovalve works in distributing the heat accordingly. It's way more complicated than this because there are various scenarios based upon exterior temp, interior temp, battery pack temp, etc but it'd literally take 4000 words to type all the various scenarios and how the Octovalve redirects the refrigerant accordingly. There are numerous vides on YouTube that can explain things visually if you want ot learn more.

 

[mark95476]

I'm learning so much from this awesome thread.

pt19713: Huge thanks!