Preheating battery in cold weather use.

[evJOULE]

@Big Earl that would do it. Thanks!

 

[evJOULE]

@Big Earl, do you know the software version of your car at the time you did the test? It appears at first glance that our cars are operating very differently. After taking a closer look at the photos you posted, it would seem impossible for you to arrive at your car in the morning with cold battery status icons if it was plugged in overnight. Just trying to think of all the possible reasons, do you think it could have anything to do with the level the battery was discharged to? I noticed that your test was done when the battery SOC was below 50%. I am not typically getting down that low before plugging in again. I don't have any software that will let me monitor the current draw from the wall, but I can basically do the same thing by confirming that the cold battery status icons disappear while a small amount of range is added after it is plugged in and the scheduled charge time is delayed.

Thanks again for your post.

 

[Big Earl]

@Big Earl, do you know the software version of your car at the time you did the test? It appears at first glance that our cars are operating very differently. After taking a closer look at the photos you posted, it would seem impossible for you to arrive at your car in the morning with cold battery status icons if it was plugged in overnight. Just trying to think of all the possible reasons, do you think it could have anything to do with the level the battery was discharged to? I noticed that your test was done when the battery SOC was below 50%. I am not typically getting down that low before plugging in again. I don't have any software that will let me monitor the current draw from the wall, but I can basically do the same thing by confirming that the cold battery status icons disappear while a small amount of range is added after it is plugged in and the scheduled charge time is delayed.

Thanks again for your post.

I never said it was plugged in overnight. I plugged it in at 7:55 PM after it sat outside in the cold for several hours and turned off the charging station because our off-peak power rates don't start until 9:00 PM, which is when I started this test (more like 9:10 PM).

Looking back at the graph, it was heating the battery for 15 minutes or so when I plugged in before I noticed it and turned off the charging station at about 8:10 PM.

Software version was and still is 2018.50.6

 

[x t2m x]

Informative post folks, thanks.

I'm disappointed that IF I do start with cold battery in the morning, I commute 43 km at 110-120 km/hr and still have the Batt. snowflake displayed when arriving at destination.

 

[evJOULE]

@Big Earl I think you misunderstood me. I was comparing your test to my experience. In other words, based on what you are showing, I wouldn't expect that you would ever arrive to your car and see cold battery status icons while it is plugged in, even when your scheduled charge time is delayed for later. But that is what happened in my case. As I said, my car was plugged in the late afternoon and was set to charge immediately to 90% SOC. The charge probably finished about 2.5 hours later at 20:30. The car then sat plugged in fully charged until I used it the next morning. The average overnight temp was -27C. Returning to the car without preheating, I noticed all cold battery status icons were visible. The only explanation I can think of is that battery heating doesn't activate if the battery is full, or in my case at a 90% SOC. What I understand from reviewing the pictures you provide is that the Model 3 will activate battery heating when needed if it is plugged in. That is not what happened in my case. I will try and duplicate your scenario by cold soaking the batteries until the cold status icons appear. I will then plug in and set the charge time to start several hours later. If my car reacts according to the images you show, the cold status icons should disappear within 15 minutes and I should see a small gain in range before the next scheduled charge time.

 

[Shock-On-T]

Apologies if this has already been mentioned up-thread, but just FYI the energy/range is not lost when the battery is cold.
By the time the battery is depleted it will have warmed up enough to be able to give all the energy back.
Driving in cold uses more energy, and that reduces range, but not because the cold 'steals' energy from the battery.

 

[RavenM3]

my experieces this winter at -30c
warming interior to 20c - the car redirects heating away from interior, resulting in a cold interior unless i reduce speed to 60 km/hr
warming interior to 'high' for 30 min before leaving and i have no issues . snow flake is no longer and regen returns sooner
note - one morning a message appeared, 'temporary reduced engine power' i assume to keep me ang battery warm. ok by me and didnt notice reduction anyway.
also, charger restarted some mornings.
Tesla seems to be experimenting to solve the issue. they're getting close.
is loss of regen during cold really an issue? not for me.
i hope they eventually have an app option for "extra cold weather" because it effects us hwy drivers very different. the wind chill requires high energy to keep every thing warm until everything gets to normal operating temp

 

[RavenM3]

my experieces this winter at -30c
warming interior to 20c - the car redirects heating away from interior, resulting in a cold interior unless i reduce speed to 60 km/hr
warming interior to 'high' for 30 min before leaving and i have no issues . snow flake is no longer and regen returns sooner
note - one morning a message appeared, 'temporary reduced engine power' i assume to keep me ang battery warm. ok by me and didnt notice reduction anyway.
also, charger restarted some mornings.
Tesla seems to be experimenting to solve the issue. they're getting close.
is loss of regen during cold really an issue? not for me.
i hope they eventually have an app option for "extra cold weather" because it effects us hwy drivers very different. the wind chill requires high energy to keep every thing warm until everything gets to normal operating temp

i should clarify.
i was warming interior to 20c for 45 min before leaving
now i set to "High" and problem solved

 

[evJOULE]

@RavenM3 I agree, I would prefer to have regen available, but it is not a really big deal, and especially not in place of battery life. And you are right, preheating the cabin before departure is the way to do it especially when the car is plugged in, but my efforts here were really to see if I could get the battery heating system to kick in. I was surprised to find a cold battery status when I did not preheat the cabin. Until @Big Earl shared his experience, I was starting to form the opinion that the Model 3 doesn't in fact have an ability to heat the battery other then drawing power from it to heat the cabin, or drive the car. I still can't explain why the battery would display a "cold status" if it was plugged in, unless the Model 3 does not start battery heating while the battery is fully charged.

 

[BrandonLive]

Model 3 is kind of like the S & X in range mode: when preconditioning, the battery is only heated to a level that provides full propulsion as opposed to being heated to a point that allows a certain amount of regen. When plugged in and charging, it will heat to a level that allows for charging.

I don’t think this is accurate. My experience has been that while charging, the battery isn’t heated at all. After a short slow drive to a 120kw supercharger with a <40% charged cold-soaked battery, the charge rate was low and immediately started gradually decreasing as the battery got colder. Having the heat on in the car seemed to make no real difference either way.

A day later I did the same thing but accelerated and regen braked frequently over a slightly longer drive, until regen dots were gone, to a 72kw supercharger, and it charged substantially faster and didn’t slow down until the charge got higher.

I then read that the Model 3 doesn’t have a dedicated battery heater, and can only warm the battery via the motor while actually driving. Do you have information suggesting this is not the case?

 

[evJOULE]

I don’t think this is accurate. My experience has been that while charging, the battery isn’t heated at all. After a short slow drive to a 120kw supercharger with a <40% charged cold-soaked battery, the charge rate was low and immediately started gradually decreasing as the battery got colder. Having the heat on in the car seemed to make no real difference either way.

A day later I did the same thing but accelerated and regen braked frequently over a slightly longer drive, until regen dots were gone, to a 72kw supercharger, and it charged substantially faster and didn’t slow down until the charge got higher.

I then read that the Model 3 doesn’t have a dedicated battery heater, and can only warm the battery via the motor while actually driving. Do you have information suggesting this is not the case?

There are some technical descriptions of the Model 3 that explain how its motor can draw current to generate heat without applying torque to the drive wheels. So in other words, while the car is parked and I am assuming plugged in. Doing away with a dedicated battery heater like in the S and X was apparently a cost saving measure in the Model 3. Have a look at the images @Big Earl has provided above. He was able to show that in fact the Model 3 can use its motor while parked to heat the battery. Having said that, I have tried numerous things with the car to demonstrate its battery heating function to no avail, while the printed information provided by Tesla on this topic is vague at best. Battery heating with the Model 3 is a little harder to demonstrate because there doesn't appear to be an icon indicator in the mobile app like with the S and X.

I am waiting for the temp to drop down again so that I can try duplicating what he did, but it still doesn't explain why a Model 3 that is plugged in over night would have a cold battery status the next morning. The only explanation I can think of is that while @Big Earl connected a cold soaked battery to start charging about 1.5 hours after it was plugged in, I connected a warm battery and started charging immediately. I am assuming with the extreme cold temperatures that occurred on that particular night, the battery cooled down after it finished charging while it sat for 12 hours, and I'm guessing that because the battery was fully charged, it didn't initiate the battery heating cycle. But who can say for sure unless Tesla offers to provide better details on the topic.

 

[MP3Mike]

Doing away with a dedicated battery heater like in the S and X was apparently a cost saving measure in the Model 3.

It is likely also a reliability improvement, as some people have reported coolant heater failures on the Model Ss.

 

[DrSmile]

The car does heat the battery through the motor when plugged in and the temperature is low. When I plug in my Model 3 to a 110 volt outlet the car doesn't charge at all - all the incoming power is diverted to run the motor to heat the battery. Once the battery warms up the battery starts to charge.

 

[Big Earl]

@Big Earl I think you misunderstood me. I was comparing your test to my experience. In other words, based on what you are showing, I wouldn't expect that you would ever arrive to your car and see cold battery status icons while it is plugged in, even when your scheduled charge time is delayed for later. But that is what happened in my case. As I said, my car was plugged in the late afternoon and was set to charge immediately to 90% SOC. The charge probably finished about 2.5 hours later at 20:30. The car then sat plugged in fully charged until I used it the next morning. The average overnight temp was -27C. Returning to the car without preheating, I noticed all cold battery status icons were visible. The only explanation I can think of is that battery heating doesn't activate if the battery is full, or in my case at a 90% SOC. What I understand from reviewing the pictures you provide is that the Model 3 will activate battery heating when needed if it is plugged in. That is not what happened in my case. I will try and duplicate your scenario by cold soaking the batteries until the cold status icons appear. I will then plug in and set the charge time to start several hours later. If my car reacts according to the images you show, the cold status icons should disappear within 15 minutes and I should see a small gain in range before the next scheduled charge time.

It stops heating the battery when it is finished charging. Continuing to run the heat would be a waste of energy. It only heats in the first place to allow charging... once charging is complete, there is no more need for it to be kept warm. What you experienced sounds normal.

 

[Big Earl]

I don’t think this is accurate. My experience has been that while charging, the battery isn’t heated at all. After a short slow drive to a 120kw supercharger with a <40% charged cold-soaked battery, the charge rate was low and immediately started gradually decreasing as the battery got colder. Having the heat on in the car seemed to make no real difference either way.

A day later I did the same thing but accelerated and regen braked frequently over a slightly longer drive, until regen dots were gone, to a 72kw supercharger, and it charged substantially faster and didn’t slow down until the charge got higher.

I then read that the Model 3 doesn’t have a dedicated battery heater, and can only warm the battery via the motor while actually driving. Do you have information suggesting this is not the case?

Charging at a Supercharger requires a much higher battery temperature than level 2 charging does. Given that the mass of the battery is 1,000 pounds, it could take a couple hours or more for the active battery heating at 2.5 kW to get it warm enough to accept 120 kW.

 

[Shock-On-T]

Just to clarify @Big Earl , if you charge to 100%, then during the night the battery gets very cold, then the next day the battery warms up to the same temperature as yesterday, then you haven't lost any energy, the range is the same.
In the same way, if you start driving with a cold battery, after a while the internal resistance of the battery will warm it up, and you will regain access to the energy of the warm battery.
If you are in an S or an X with range mode off, then you will waste some energy heating the battery using the battery heater, basically hastening the inevitable warming at extra cost, but this isn't necessary.

 

[taraquin]

I don't think comparing Model 3s batteryheating to range mode on S and X is accurate. One of the major differences is that the battery in 3 seems to tolerate cold weather better than S and X. Several owners tslk about having some regen after the car has been parked in -5C for many hours without charging or preheating. That never happends in S and X. After a couple of hours in the cold regen dissapears in S and X. If temp is 0C or below, all regen goes away after a few hours. The Nissan Leaf and Kia Soul can do some regen even if temps are below 0C.

 

[Big Earl]

I don't think comparing Model 3s batteryheating to range mode on S and X is accurate. One of the major differences is that the battery in 3 seems to tolerate cold weather better than S and X. Several owners tslk about having some regen after the car has been parked in -5C for many hours without charging or preheating. That never happends in S and X. After a couple of hours in the cold regen dissapears in S and X. If temp is 0C or below, all regen goes away after a few hours. The Nissan Leaf and Kia Soul can do some regen even if temps are below 0C.

I think that has more to do with chemistry and/or control programming and less to do with heating strategy.

S & X will actively heat the battery up to a higher setpoint than the 3.

 

[taraquin]

I think that has more to do with chemistry and/or control programming and less to do with heating strategy.

S & X will actively heat the battery up to a higher setpoint than the 3.

My point is that the 3 gets away with different behaviour than 3 due to different chemistry. At -10C batteryheater will start with range mode in Model S. If charger outputs more than 6kW then batteryheater will always start if temp/regen is below 15kW. Modelv3 does seem to makemotor heat battery sometimes at a certain temp when charging is done or even when charging is slow. I have only seen this once in my Model S when temp was -20C. S and X needs the batteryheater due to bad chemistry in cold weather.

 

[ThosEM]

Model 3 is kind of like the S & X in range mode: when preconditioning, the battery is only heated to a level that provides full propulsion as opposed to being heated to a point that allows a certain amount of regen. When plugged in and charging, it will heat to a level that allows for charging.

Thanks, Big Earl! for checking into this with a Juicebox. It would sure be nice if Tesla would document this stuff better, but they evidently don't cater to those of us with an interest in how things actually work.