Battery heating while preconditioning cabin

[Brock-WI]

I can confirm our 2018 M3 single motor looks just like the one above with the red battery while using the remote climate control.

As others have noted I wish we could shut off the battery heating part. I get why they do this and I get it being the default behavior, but I wish here was an option to not pre-heat the battery as well. When I leave work after working 12 hours at 0F or -18C and drive 3 miles home, there is no point warming up the battery. Also as others have noted, I don't understand once I am in the car it shuts off the "afterburners" and stops warming the battery. Why is it only important to do when I am not in the car and driving?

I am just trying to understand the logic...

 

[vogz]

I can confirm our 2018 M3 single motor looks just like the one above with the red battery while using the remote climate control.

As others have noted I wish we could shut off the battery heating part. I get why they do this and I get it being the default behavior, but I wish here was an option to not pre-heat the battery as well. When I leave work after working 12 hours at 0F or -18C and drive 3 miles home, there is no point warming up the battery. Also as others have noted, I don't understand once I am in the car it shuts off the "afterburners" and stops warming the battery. Why is it only important to do when I am not in the car and driving?

I am just trying to understand the logic...

I agree. I noticed the battery warming icon the other day heating my car up at the end of my *sugar* at work. Tonight I had it again after my car sat outside in 18-20F weather. I ran the climate for about 5 minutes to warm up the car and it ate up 2% of my battery. I only have a 10 minute commute, and want to get into a warm car. (it's one of the reasons I bought the Model 3), but warming it up for 5 minutes uses more energy than driving home with the heat set to over 70F.

 

[Schulmann]

Warming the battery pulls around 3.5KW in average. It heats up the stator between 50-70C. it is a Very effective method to warm the battery. There are two ways to trigger this process:
Head to a supercharger in the navigator and stop at a redlight (TM3 will heat stator). It can't do it while driving.
Precondition habitacle in the cell phone app , while TM3 is stopped.

It is an important feature when charging or TM3 need regeneration (Heading down from hill).

While driving it is a lengthy process to heat up a cold battery, might take 2-3 hours to reach 20C at 0C.
Even a short 1-2 min preconditionning can accelerate battery heat up because stator quickly reaches 40C.

 

[Gasaraki]

Can anyone confirm the behaviour of cabin/battery heating that happens in my model 3? Everytime when I start cabin heater from app the battery heater kicks in and motors pull the 7kw like they do when heating battery. Checked from scanmytesla and total battery draw can be as high as 14kw. 7kw for the motors, 6kw for cabin heater and rest for seat heaters, computers and so on. It doesn't matter if charging or not, so not even 11kw charger is able to top that and range loss before driving is very fast and noticeably.

When I was testing temperature was +10C and cell temperature was +20C, so seems like totally unnecessary and wasted energy. It also really adds the total energy consumption, especially when driving short trips at winter times. 15min of heating can now consume as much as 3.5kwh, which alone is about 20km worth of range. Now lets say you drive 10km with 200wh/km, total energy consumption is now 550wh/km! Range loss before drive could also be a problem if already stretching close to the maximum range at cold weather.

Imo this should be behind an option, and if it was, it would be a great thing to have a manual battery heater available. But is this just a fluke with my car and should I contact service center or can anyone else confirm? My solution now is to not preheat if I don't absolutely have to (frozen windows for example). I hate wasting energy so much that it nearly doubles or triples the consumption compared to only driving. Also don't like that something so fundamental basic function of the car changes without notice.

It is 100% true that when you use the preheat button, it preheats the batteries also. I agree they should put the preheat battery and preheat cabin as separate options.

 

[camalaio]

I can confirm our 2018 M3 single motor looks just like the one above with the red battery while using the remote climate control.

As others have noted I wish we could shut off the battery heating part. I get why they do this and I get it being the default behavior, but I wish here was an option to not pre-heat the battery as well. When I leave work after working 12 hours at 0F or -18C and drive 3 miles home, there is no point warming up the battery. Also as others have noted, I don't understand once I am in the car it shuts off the "afterburners" and stops warming the battery. Why is it only important to do when I am not in the car and driving?

I am just trying to understand the logic...

The Logic: People were begging Elon for it on Twitter so they could have strong regen even in the cold. The manual mentions it's for regen now, there's not really a secondary benefit beyond that.

Which really sucks, because like in your scenario, it's gargantuanly wasteful. I started not preheating the car at all to save energy, but it'll still actively warm the battery while driving when cold enough (not just for cabin preheating).

To give a sense to others about how wasteful this is, I can normally get better-than-rated range in summer (even with AC on), or pretty much equal to rated when accounting for standby drain (145Wh/km, ish). Last winter when this battery heating feature wasn't in place, I trended around 200Wh/km at worst. This winter, with the battery warming "feature", I'm trending at closer to 1200Wh/km. That's simply insane. For areas with fairly dirty electricity generation, this puts the Model 3 as the worse option for the environment by far compared to ICE vehicles (considering it's about even in summer).

It really sucks that I entered into Tesla//EVs for "green" reasons, and they "update" my car to be this wasteful all so regenerative braking is consistent. The car did not do this when I first got it. It shouldn't be a surprise, but this tells me Tesla will do things to make people feel good rather than do something that's actually a net good for energy usage.

Making one of the most efficient EVs in motion means squat when it's the most wasteful EV in park.

/rant

Warming the battery pulls around 3.5KW in average. It heats up the stator between 50-70C. it is a Very effective method to warm the battery. There are two ways to trigger this process:
Head to a supercharger in the navigator and stop at a redlight (TM3 will heat stator). It can't do it while driving.
Precondition habitacle in the cell phone app , while TM3 is stopped.

It is an important feature when charging or TM3 need regeneration (Heading down from hill).

While driving it is a lengthy process to heat up a cold battery, might take 2-3 hours to reach 20C at 0C.
Even a short 1-2 min preconditionning can accelerate battery heat up because stator quickly reaches 40C.

Bold part my emphasis, and I have a question (since I'm in my own bubble and I'm trying to understand).

You say it's important, but what exactly is important? Or I guess, "why"? Is it important to you, or do you feel it's important for some other reason than personal preference? Do you find that you don't have enough regen power for a hill if it doesn't preheat? Sorry for the barrage of questions

I guess to offer my perspective, I wouldn't rate it as important for hills because I still have traditional friction brakes and a brake pedal.

 

[derotam]

but it'll still actively warm the battery while driving when cold enough (not just for cabin preheating).

Yes if it gets cold enough it will try to heat the battery but that would only be for protecting the battery. At 0C the car won't even allow charging because charging at that temperature could damage the battery. As far as heating the battery WHILE driving it can only do so, and to a limited extent at lower speeds in a RWD vehicle. Lower speeds being <30mph. An AWD is a bit better because it can use the front motor for heat when it isn't using it as a drive motor.

 

[GZDongles]

I enjoy the ability to preheat the car and battery, especially before long trips where I need to maximize range. For 90% of my driving I agree that pre conditioning the battery is extremely wasteful. If the main argument for preconditioning is to have consistent regen feel, it seems like it should be possible to blend regen and physical brakes using software to mimic the experience regardless of battery SoC or temperature.

 

[camalaio]

I enjoy the ability to preheat the car and battery, especially before long trips where I need to maximize range. For 90% of my driving I agree that pre conditioning the battery is extremely wasteful. If the main argument for preconditioning is to have consistent regen feel, it seems like it should be possible to blend regen and physical brakes using software to mimic the experience regardless of battery SoC or temperature.

And other cars do blend regen and brakes. IIRC that's part of the job of the Bosch iBooster used in many EVs, which the Model 3 also uses.

Tesla is even sort of clever about regen right now, despite not blending friction brakes. If you are 100% limited for regen (that is, no regen) the car still allows enough regen power to compensate against things like heating. So if the car is drawing 5kW for climate control for example, it does actually regen brake with 5kW of power (it's just limiting the net power to the battery at 0kw).

Further, for the Hold stop mode, the car applies reverse power in some cases to give the same braking feel even though it's consuming energy, not regenerating it.

 

[rrolsbe]

And other cars do blend regen and brakes. IIRC that's part of the job of the Bosch iBooster used in many EVs, which the Model 3 also uses.

Tesla is even sort of clever about regen right now, despite not blending friction brakes. If you are 100% limited for regen (that is, no regen) the car still allows enough regen power to compensate against things like heating. So if the car is drawing 5kW for climate control for example, it does actually regen brake with 5kW of power (it's just limiting the net power to the battery at 0kw).

Further, for the Hold stop mode, the car applies reverse power in some cases to give the same braking feel even though it's consuming energy, not regenerating it.

How did you convince yourself that the car uses regen when the car is drawing XKW for the climate control? SMT? If the battery is too cold or full to accept regen, crank the heater on the downhill slopes better than using the friction brakes. I would guess if you have two regen dots or more using the heat on downhill slopes could be a win.

 

[rrolsbe]

I created a thread awhile back wondering whether the regen power could be used for things other than charging the traction battery. I do not know if the Traction motor(s) can generate regen power and send it to its own motor stator windings? I would think the rear motor could regen and send that approx 3.5KW of power to the front stator windings. This would serve two purposes give the car some/more regen and warm the traction battery quicker which over time would give even more regen. Going downhill with NO regen and a cold traction battery would generate almost no heat, if the regen power can't be sinked to other high voltage car sources drawing power.

This post is a bit off topic buy it does relate to heating the traction battery.

 

[camalaio]

How did you convince yourself that the car uses regen when the car is drawing XKW for the climate control? SMT? If the battery is too cold or full to accept regen, crank the heater on the downhill slopes better than using the friction brakes. I would guess if you have two regen dots or more using the heat on downhill slopes could be a win.

First by sound (limited regen has a sound... sort of) then by feel (I can tell the difference between the car coasting and regen braking). It did not sound like it was applying reverse power, which in contrast doesn't really make a noticeable sound.

After that I made a mental note to check SMT on the next drive, and it seemed to loosely suggest what I was observing.

Of course, even 5kW of regen is barely noticeable at any reasonable speed. By strength, it only becomes apparent probably below 20km/h or so, and even then it's pretty weak. IIRC around 15kW limit of regen is where people feel like they have effectively no regen except at low speeds.

I created a thread awhile back wondering whether the regen power could be used for things other than charging the traction battery. I do not know if the Traction motor(s) can generate regen power and send it to its own motor stator windings? I would think the rear motor could regen and send that approx 3.5KW of power to the front stator windings. This would serve two purposes give the car some/more regen and warm the traction battery quicker which over time would give even more regen. Going downhill with NO regen and a cold traction battery would generate almost no heat, if the regen power can't be sinked to other high voltage car sources drawing power.

This post is a bit off topic buy it does relate to heating the traction battery.

I lack data on this, but I think the car does do this (e.g. for preheating for Supercharging). Sort of. There are at least two modes it has for generating waste heat, and it seemed like one of them is overdriving the rear while the front drags for regen... or maybe it was reverse power. I don't recall anymore.

 

[derotam]

I created a thread awhile back wondering whether the regen power could be used for things other than charging the traction battery. I do not know if the Traction motor(s) can generate regen power and send it to its own motor stator windings? I would think the rear motor could regen and send that approx 3.5KW of power to the front stator windings. This would serve two purposes give the car some/more regen and warm the traction battery quicker which over time would give even more regen. Going downhill with NO regen and a cold traction battery would generate almost no heat, if the regen power can't be sinked to other high voltage car sources drawing power.

This post is a bit off topic buy it does relate to heating the traction battery.

That is an interesting idea but the problem is that at this time the car only pushes a max of about 3.5kW to the stators for battery warming. 3.5kW of regen is not very much at all and is what you get when you are going <10mph so it would basically be useless.

 

[Tonybvi]

I have a steep hill down from my house on a rural road which doesn’t get ploughed in winter. It’s pretty hairy descending this with no regen so I have to use brakes which I hate doing in snow. To maximise regen I have to preheat the battery even if only popping down to the shops. Rather pay for the power used to preheat the battery and give me full regen than slide off the road!’

 

[SigNC]

That is an interesting idea but the problem is that at this time the car only pushes a max of about 3.5kW to the stators for battery warming. 3.5kW of regen is not very much at all and is what you get when you are going <10mph so it would basically be useless.

One of the big reasons why dual motor cars warm the battery so much faster. not only are there 2 motors creating heat the first one can basically be dedicated to heat where as when it's rear only, as i understand it, it's only creating 3.5kW of heat when it's not under significant load.

 

[derotam]

One of the big reasons why dual motor cars warm the battery so much faster. not only are there 2 motors creating heat the first one can basically be dedicated to heat where as when it's rear only, as i understand it, it's only creating 3.5kW of heat when it's not under significant load.

Yes, and with the AWD under "normal" highway driving when there is no need for AWD the front motor is not really used for driving so when pre-conditioning in route to a supercharger it can actually attempt to warm up the battery a bit, unlike the RWD version(which I have).

 

[camalaio]

I have a steep hill down from my house on a rural road which doesn’t get ploughed in winter. It’s pretty hairy descending this with no regen so I have to use brakes which I hate doing in snow. To maximise regen I have to preheat the battery even if only popping down to the shops. Rather pay for the power used to preheat the battery and give me full regen than slide off the road!’

The friction braking system is objectively much better than regen for control and stopping in snow, since friction brakes always use all four wheels somewhat independently (regen does not). Although if regen feels better to you, that's a separate point I guess.

 

[rrolsbe]

That is an interesting idea but the problem is that at this time the car only pushes a max of about 3.5kW to the stators for battery warming. 3.5kW of regen is not very much at all and is what you get when you are going <10mph so it would basically be useless.

I would agree but if both motors and the heater were drawing power it could approach 14KW and if the battery was warm enough to accept some regen it might be acceptable. I believe the max regen on my 2018 RWD is somewhere around 60KW. Bottom line using any regen power should benefit range and require slightly less use of the friction brakes; likewise, supplying regen power directly to HV components should have less loss than routing it through the traction battery.

 

[Tonybvi]

The friction braking system is objectively much better than regen for control and stopping in snow, since friction brakes always use all four wheels somewhat independently (regen does not). Although if regen feels better to you, that's a separate point I guess.

You may well be correct but when I lived in Norway I had to undergo training in driving on snow and ice. The golden rule that was drilled into me was try at all costs to avoid braking, even gently, as this can cause the wheels to start skidding. We were taught to use our gears or to select low when driving automatics. For me strong regen is equivalent to low gearing when going down hill. Incidentally another trick I was taught, which goes against the grain somewhat, is to accelerate if the wheels lose traction as this brings the wheel speed up to match the road speed again.

 

[derotam]

I would agree but if both motors and the heater were drawing power it could approach 14KW and if the battery was warm enough to accept some regen it might be acceptable. I believe the max regen on my 2018 RWD is somewhere around 60KW. Bottom line using any regen power should benefit range and require slightly less use of the friction brakes; likewise, supplying regen power directly to HV components should have less loss than routing it through the traction battery.

And 14kW matches up to just about the 10mph mark equivalent. Here's a graph I made early 2020 you might find interesting, imgur.com

 

[rrolsbe]

And 14kW matches up to just about the 10mph mark equivalent. Here's a graph I made early 2020 you might find interesting, imgur.com

Thanks for the graph! If you draw a horizontal line at the 14KW/10MPH point the area under the curve appears to be about 1/4 of the total area under the green curve on your graph. Better than nothing if I am analyzing this correctly.