Passive pack heating mode while driving

[Todd Burch]

So we know a few facts:

1. Batteries have internal resistance, and both the battery and the motor generate heat while driving.
2. Model S has an active pack heater that consumes a large amount of energy to heat the pack while driving in colder weather.

So i've often wondered why there isn't a "passive heating" mode while driving.

Suppose you have a long trip and need as much range as you can get. Wouldn't you prefer to have power and regen limits vs. burning 4-600 Wh/mi for quite a while on the trip?

In those cases, I'd rather the pack just heat up naturally...much more slowly, while maintaining power and regen limits as necessary. This would result in significantly smaller range loss on cold days.

So why hasn't Tesla done this (at least as an option)? If it's ok to drive the car when the pack's cold, why not just let it warm up passively, as long as power/regen limits are respected?

 

[islandbayy]

It can. Go into settings, and turn on Range Mode. It will lower the thresh hold down to the absolute bare minimum before the pack heater comes on.


For the best battery life, lithium cell operation with a Major load should be above 20*F, and ok down to 5*F at reduced power, below that, EXTREME Reduction in power (when it was -30F, my accel was limited to 30kW, not much. It quickly went up. In that case, no matter what, pack heater is coming on. Tesla is trying to balance between performance, range and battery life. Given the nature of sending their product out to consumers, and no consumer is cookie cutter, they are trying to cover all bases. So If you dont want the pack heater coming on until it's REALLY COLD, turn on Range mode. Note, it will also reduce your heaters out put. But, as usual, your always best off trying to preheat on wall power.

 

[Todd Burch]

My understanding was that this only affected cabin, and not pack heating. Guess I need to check the manual.

 

[jerry33]

My understanding was that this only affected cabin, and not pack heating. Guess I need to check the manual.

Range mode or not certainly acts as if it affects pack heating--at least in my car. It takes a very long time (just under an hour's driving) for the regen limitation to completely go away at -5C--and that's after preheating.

 

[islandbayy]

Range mode or not certainly acts as if it affects pack heating--at least in my car. It takes a very long time (just under an hour's driving) for the regen limitation to completely go away at -5C--and that's after preheating.

Sure as heck does. Just a simple test for one to see. Hop in your car on a cold day (without preheating the vehicle). Hit the brake so the car comes online. Just watch the energy draw (orange bar) rise (leave HEAT OFF) with range mode off. After about 2 minutes of the orange bar being on, the car will say Battery is Heating. Now, go into settings and turn on range mode (still keep heat off!). It will take about 30 seconds or so for the power to ramp down, but it will. Eventually (unless it is BLISTERING COLD OUT) the bar will go down to nothing or extremely low.

 

[Cottonwood]

Sure as heck does. Just a simple test for one to see. Hop in your car on a cold day (without preheating the vehicle). Hit the brake so the car comes online. Just watch the energy draw (orange bar) rise (leave HEAT OFF) with range mode off. After about 2 minutes of the orange bar being on, the car will say Battery is Heating. Now, go into settings and turn on range mode (still keep heat off!). It will take about 30 seconds or so for the power to ramp down, but it will. Eventually (unless it is BLISTERING COLD OUT) the bar will go down to nothing or extremely low.

Here is a corollary of of this method that seems to work well for me winter hypermiling. I preheat in a 50˚ F. garage for multiple 30 minute App pre-heat cycles, 1.5 - 2.5 hours on shore power, then do the winter driving in range mode. This pre-heats the battery and cabin. I find with this method, I use only slightly more energy per mile over good weather driving. My theory is that with the battery starting warm, and with the waste heat from driving helping keep it warm, I need very little, if any, battery heat. In addition, with the cabin interior starting warm, the only cabin heat that I need is for canceling the heat lot to the exterior. Of course, all bets are off if I hit slush, new snow, or icing conditions...

 

[Doug_G]

Here's something you may not know - Range Mode affects preheating on AC power. That is totally counterproductive! You want the car to be as toasty as possible before you have to unplug. So be sure to turn off Range Mode if you plan to preheat your car.

 

[widodh]

Here's something you may not know - Range Mode affects preheating on AC power. That is totally counterproductive! You want the car to be as toasty as possible before you have to unplug. So be sure to turn off Range Mode if you plan to preheat your car.

What? That's weird.

I turned on Range Mode some time ago and it's saved in my profile. It works just fine for me in the -5C to 5C temperatures we are seeing here now, so I didn't bother turning it off. Why would Range Mode affect this? Probably a software feature which isn't there yet. The system which controls the heater probably doesn't "know" if the car is using wall power or not.

 

[Discoducky]

What? That's weird.

I turned on Range Mode some time ago and it's saved in my profile. It works just fine for me in the -5C to 5C temperatures we are seeing here now, so I didn't bother turning it off. Why would Range Mode affect this? Probably a software feature which isn't there yet. The system which controls the heater probably doesn't "know" if the car is using wall power or not.

Agreed, but guessing, since it seems obvious to us, that it will be obvious to the engineers as well or maybe there is a weird limitation to Linux as I can't imagine they would want to allow shore power to actively heat the battery once the app activates cabin heating when in range mode.... especially when in range mode!!!

 

[jerry33]

I turned on Range Mode some time ago and it's saved in my profile. It works just fine for me in the -5C to 5C temperatures we are seeing here now, so I didn't bother turning it off. Why would Range Mode affect this? Probably a software feature which isn't there yet. The system which controls the heater probably doesn't "know" if the car is using wall power or not.

Mine works as Doug describes. There is limited battery heating when plugged in and using range mode.

 

[L@urens]

I can confirm that with
- Range Mode ON - I get less pack heating, it takes longer for the regen limit to disappear
- Range Mode OFF - Heating up to 10kW on idle - message "Power will improve" shows.

 

[Doug_G]

What? That's weird.

Yes, it is weird, but it is definitely true. And as I said, highly counterproductive!

At this point I've given up on Range Mode entirely. For long trips I thoroughly AC preheat with Range Mode OFF prior to departure (if I have time I'll do it for an hour, turning it back on again when it turns off after 30 minutes). Then when I leave I don't bother turning Range Mode on, because I don't think it is useful. Once the drive train and cabin is warmed up, the HVAC takes surprisingly little power.