Battery Heating May Have Changed

[Rocky_H]

It has long been the common belief here on TMC that if one preheated the cabin, while on shore power, with range mode off, the battery pack would also be heated, provided the pack was cold.

I don't think so. I thought it was really well known for years that the battery heater doesn't turn on in that case. At least has been known for a really long time on the Tesla.com forum (3+ years). I guess I hadn't looked for it over here on TMC too much, since I joined here about a year later.

 

[Electric700]

I've taken a look at other fields as well from this morning when I did a preheat which is of interest:
battery_current, charger_current and charger_voltage.
Before starting preheating battery current was at -0.3A (a load of 100W+ or so since I use the always connected setting in my car).

When I started heating battery_heater_on remained false, but I can see current flowing from both the wall and the battery.
Iit did at one point pull 14.7 amps from the battery and 12A (at 229V) from the wall. If we assume a conservative (?) pack voltage of 390V (SOC at 80%) that gives us a power consumtion in the car at: 14.7A x 390V + 12A x 229V = 5733W + 2748W = 8481W total power

Shouldn't this mean that both battery and cabin heating is active? I have read elsewhere on this forum that the car has 6kW cabin heater and 5.5kW battery heater, and since total consumed power is more than the cabin heater is able to consume alone I assume the power is distributed between pack and cabin heating?

How much total power do your cars consume when preheating in cold temperatures?

Really interesting information there, thanks. I am thinking that you are probably right, and both the battery heater and cabin heater were active. If it's true, it would make sense that Tesla would have the battery heater turn on when the cabin heater is active. It's possible they changed/improved this behavior recently.

There were other cases I saw here within the past month where scheduled charging wasn't working correctly when it was cold (e.g. 0 degrees C), but I'm not sure if Tesla fixed that issue yet. It was likely caused by the battery heater not coming on when charging was supposed to start, thus the battery remained too cold to charge even hours after the charge was scheduled. Until Tesla fixed it (or will fix it), one workaround was to charge immediately after driving.

 

[rypalmer]

I took a closer look at some cold soaked charging data from the past few months. I don't see the Battery Heater On value ever being True, during charging, when the climate is on, etc. I'd lean towards this value having been removed from the API feed, rather than the heater not being used.

On another note, we have such a wealth of data that comes from this API endpoint, why not pass along battery temperature values as well? Is that value really that proprietary?

 

[bjornb]

Another data point:
I also activated preheating before leaving work today (outdoor parking, not plugged in). Highest battery current was 24.8A, that means about 9,5kW was pulled from the battery at peak (SOC 74%, assuming pack voltage at 385V).
I also did a graph of the data (teslafi -> excel), one can see that the power falls to below 7kW after 4 minutes, but stays in the 6,5-7kW region for a while before dropping at 11 minutes to about 2kW to maintain the chosen interior temp.
If this was only cabin heating I would have expected the battery power to drop sooner, and I am thinking that the car did some battery heating in the first 10 minutes or so.

 

[hybridbear]

On another note, we have such a wealth of data that comes from this API endpoint, why not pass along battery temperature values as well? Is that value really that proprietary?

I agree!

Thanks.

Is that true for the cabin pre-heating only, or for both cabin pre-heating and driving? Also, as far as you know, has this number--8 C, or 46.4 F--changed at all recently?

Finally, do you know at what battery temperature there would be no regen limit? Do you know if this has changed? (My gut feeling is that about a year ago, give or take, the regen limit started kicking in at higher temperatures than previously, meaning the battery needed to be even warmer to not have any regen limit at all.)

Thanks again!

I've been told by local Tesla owners that have root access to their cars that the regen limits begin when the pack temperature drops below 20 C (68 F), but that the car doesn't begin heating the HVB until the temperature of the pack gets below 10 C (50 F). I have seen the pack heater running as observed by a noticeable power load on the dash power meter while stopped with HVAC off.

I am having an issue downloading my data from TeslaFi.com that is preventing me from reviewing my battery heater history. There are many times where I have arrived home with a cold battery and then have used remote HVAC through the app to try to warm the battery up. So I wonder if in those cases the pack heater would have activated.

 

[Cyclone]

With range mode off, and plugged in, if you started cabin heating now the old theory was that the battery heater would come on. So if you tried that, and then looked at the TeslaFi data to see whether or not the battery heater came on or not, that would be helpful.

If you wanted to take it a step further, you could go for a short drive, after preheating the cabin a bit, and see if the battery heater came on during the drive. Obviously I'm not going to ask you to go for a drive, though, just to test this. You could do the same test the next time the battery is cold, and you're going for a drive anyway.

Thanks for being willing to help!

I apologize Andy that I got sidetracked last night and didn't do this, and today we are 70*F instead of 45*F. I exported my history from TeslaFi. Since signing up in Oct, only ONCE has battery heater been on for me, and that was on a drive from the airport to the Supercharger a few days ago. The heater turned off even before I got to the Supercharger. I can upload the view if you like. What would you like to see?

 

[Andyw2100]

Andy, I have read in multiple threads that the battery heater comes on when plugged into shore power, range mode is off, and you start the climate control using the Tesla phone app. If you are not using the phone app, you might want to try that.

That's exactly what I've been doing, at least some of the time. (Some of the time the climate control has been started on a schedule, using Visible Tesla.) But I've done testing with the app, and TeslaFi is not showing the battery heater coming on.

 

[Andyw2100]

I don't think so. I thought it was really well known for years that the battery heater doesn't turn on in that case. At least has been known for a really long time on the Tesla.com forum (3+ years). I guess I hadn't looked for it over here on TMC too much, since I joined here about a year later.

Either you are confused, or the info on TMC and the Tesla Forums is radically different.

What has been the common understanding here is that with range mode --ON-- the battery won't preheat.

 

[Andyw2100]

I took a closer look at some cold soaked charging data from the past few months. I don't see the Battery Heater On value ever being True, during charging, when the climate is on, etc. I'd lean towards this value having been removed from the API feed, rather than the heater not being used.

On another note, we have such a wealth of data that comes from this API endpoint, why not pass along battery temperature values as well? Is that value really that proprietary?

My battery heater was on as recently as January 17, and Ryan, of Tesla Cockpit, was saying that he was seeing battery heater on as true for other cars.

It is comforting to me that you too, though, are not seeing "true" in that field.

 

[Andyw2100]

Another data point:
I also activated preheating before leaving work today (outdoor parking, not plugged in). Highest battery current was 24.8A, that means about 9,5kW was pulled from the battery at peak (SOC 74%, assuming pack voltage at 385V).
I also did a graph of the data (teslafi -> excel), one can see that the power falls to below 7kW after 4 minutes, but stays in the 6,5-7kW region for a while before dropping at 11 minutes to about 2kW to maintain the chosen interior temp.
If this was only cabin heating I would have expected the battery power to drop sooner, and I am thinking that the car did some battery heating in the first 10 minutes or so.

And during the time above, battery heater on never showed as "true", correct? This would lend more weight to the "Tesla stopped using the field in the API" theory.

Thanks!

 

[Andyw2100]

I apologize Andy that I got sidetracked last night and didn't do this, and today we are 70*F instead of 45*F. I exported my history from TeslaFi. Since signing up in Oct, only ONCE has battery heater been on for me, and that was on a drive from the airport to the Supercharger a few days ago. The heater turned off even before I got to the Supercharger. I can upload the view if you like. What would you like to see?

No need to do any more right now. Just see if you can test it some time when it is cold again. But it seems we are getting data that indicate that battery heater on field may not be being used any longer, or is being used in some flaky way.

Does it make sense to you that your battery heater would have only been on that one time? Or could this all be "bad data" of one kind or another?

 

[bjornb]

And during the time above, battery heater on never showed as "true", correct? This would lend more weight to the "Tesla stopped using the field in the API" theory.

Yes, battery_heater_on were false on all data today as well.

 

[Cyclone]

No need to do any more right now. Just see if you can test it some time when it is cold again. But it seems we are getting data that indicate that battery heater on field may not be being used any longer, or is being used in some flaky way.

Does it make sense to you that your battery heater would have only been on that one time? Or could this all be "bad data" of one kind or another?

It doesn't make sense to me. There were many times in Nov and Dec that I drove with range mode on b/c I didn't want the battery running on short trips, but in Jan, I've had range mode mostly off and expected to see the battery heater when I'm down to 15 kW of regen. I can tell you that my power meter, when in drive, at a full stop, has often been rather high because of heating, but that could have been the cabin heater.

 

[David29]

Andy, I have read in multiple threads that the battery heater comes on when plugged into shore power, range mode is off, and you start the climate control using the Tesla phone app. If you are not using the phone app, you might want to try that.

It's also stated that way in the Tesla owner's manual, so it is not only the opinion of folks posting here on TMC.

 

[Rocky_H]

Either you are confused, or the info on TMC and the Tesla Forums is radically different.

What has been the common understanding here is that with range mode --ON-- the battery won't preheat.

Huh. I just went back and researched it and found what was going on there. I wasn’t confused about it; I’ve just been on the forum TOO long and my information got outdated. Sorry about that everyone. It used to function how I said, but that functionality got changed from a firmware update and the owner’s manual updated to match. It’s tough to keep up with all of the feature changes on the car sometimes. I had been doing most of my really in depth research on everything back in 2013, so that was probably where I read about the original functionality, where it would only turn on the battery warming if you set heating to “HI”. It seems it was around mid/late 2014 that the firmware update changed it to activate battery heating with any cabin heating. See here:

How to "preheat the battery"? | Page 2 | Tesla Motors
November 2014

Brian H | November 14, 2014

IIRC, Elon announced that shore-warming the cabin at all levels would now trigger battery warming, not just "High". Don't know if that was latest s/w update, or cars with Autopilot, or just what is required.



How to heat 85 battery | Tesla Motors
January 2015

Bighorn | January 4, 2015

@Tabarnouche
Tesla responded to requests for the car to work that way. Firmware initiates battery warming under those circumstances.

Brian H | January 4, 2015

Originally only "High" on the climate setting warmed the battery, but then Elon says it was changed, so any pre-warming level does it.

 

[sorka]

I manually turn on the battery heater with the "max battery" setting for about 10 minutes before I depart if it's really cold in the morning. It's not enough for maximum power but it's enough to get maximum regen which is what I want when first taking off.

Would really like a way to turn this on from the app so I don't have to go out to the car 10 minutes before I leave.

 

[Andyw2100]

I manually turn on the battery heater with the "max battery" setting for about 10 minutes before I depart if it's really cold in the morning. It's not enough for maximum power but it's enough to get maximum regen which is what I want when first taking off.

Would really like a way to turn this on from the app so I don't have to go out to the car 10 minutes before I leave.

Do you use Teslafi, or another service / app that could report the "battery heater on" field? I'd like to know, if when you do use the battery heater in that way, if the API is reporting it in the "battery heater on" field.

 

[Cyclone]

I'm also leaning towards the "Tesla changed the reporting of battery_heater in the API to denote something other than simply on/off".

Last night Charlotte was in the upper 20*F. I left the house this morning at 34*F with regen limited at 30 kW initially and taking about 10 miles before it went away completely. Looking at my trip data in TeslaFi, battery_heater_on reports as false the entire time. Perhaps my car really didn't use the battery heat and just let natural heat buildup from driving do it's thing, but I must say I would be surprised. I definitely had cabin heat going though, so it could make sense that the battery was just using passive heating.

 

[Doug_G]

The pack heater comes on when you preheat from the remote app, period. Regardless of whether shore power is present or not. It has always worked this way and still does.

I don't need an app to tell me this. Simple observation - I live in a place that routinely sees -20C weather (or colder).

With a cold-soaked battery I will have no regen.

In the same conditions, if I preheat (shore power or not) I will have 50% regen.

I see this all the time.

 

[Andyw2100]

The pack heater comes on when you preheat from the remote app, period. Regardless of whether shore power is present or not. It has always worked this way and still does.

I don't need an app to tell me this. Simple observation - I live in a place that routinely sees -20C weather (or colder).

Can you use TeslaFi or Tesla Cockpit to check on the "battery heater on" field, to see if we are correct that it is not reporting the on/off status of the battery heater the way we would expect it to? If so, that would be great!