Preheating battery in cold weather use.

[evJOULE]

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.

I agree and think that the small increase in range that we see during battery heating is more likely the result of the battery warming up as opposed to energy being added (as in car is plugged in, but scheduled charge time is set to start at a later time).

 

[evJOULE]

Battery heating on the Model 3 works when it needs to work. It will work even while you're driving if the BMS determines that it's necessary. When it does heat, it only heats enough to meet the minimum temperature requirement for charging and for full propulsion power, then it stops.

Things that can trigger battery heating *if* temperature and operating conditions warrant it: preheating from the app, plugging in to charge or with a charge scheduled for a future time, supercharging, battery temperature drops below minimum safe storage level (deep into the negatives), and finally, just getting in and driving.

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, my point was as per your first quote. Even though the battery is fully charged, I would have expected that battery heating would start so that full propulsion power is kept available. I wasn't thinking that battery heating would continue the entire time the car is plugged in.

But I was also able to duplicate what you showed from your little test. I left the car unplugged all day and over night to cold soak the battery. When I opened the car to get in, the same battery heating message you described appeared when the car turned on. This to me was interesting, because the car was not plugged in. So battery heating does occur in the Model 3 even when it is not plugged in at least when the battery is fully charged. In my case, there was nearly 400km of range left in the battery. It would be nice if Tesla could clarify what battery SOC level the Model 3 is able to continue heating the battery when unplugged. And as you said, I was able to actually hear the motor actively heating, and once I plugged in, the sound coming from underneath where I would expect the motor to be increased. In my case, it took almost an hour of continuous battery heating before the cold battery status icons disappeared, and that was with climate control set to high about 15 minutes after battery heating started. Judging by the amount of time it took to rewarm the large mass of the battery, the pack temp must have been quite low in this case. But the cars behaviour and its ability to heat the battery appears different from what I observed mid December 2018. Presumably one of the updates I received since then has added improved functionality in this area. It would also be nice if Model 3 owners could access the battery heating function from inside the mobile app as a separate feature from cabin heating.

 

[diamond.g]

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.

Are we sure the 3's pack uses a different chemistry than the 100D S/X pack?

 

[derotam]

Are we sure the 3's pack uses a different chemistry than the 100D S/X pack?

I'm working on finding the reference but yes the cell chemistry changed between the 18650(S/X) and 2170 cell.

Edit: Not the reference I was looking for but this shows the cobalt reduction between the early and later Model S's and reduction further for the model S. Tesla is leading electric car batteries away from cobalt mining industry

 

[taraquin]

Are we sure the 3's pack uses a different chemistry than the 100D S/X pack?

Yes, they have for instance reduced the use of cobolt a great deal. It's still based on NCA, but there have been made different ratios between the metals.

What would be interessting to see is what temp causes regen to disappear? On Model S and X, in temps of 0C or below regen is disabled if car is left for s few hours so batterytemp matches airtemp.

 

[Big Earl]

@Big Earl, my point was as per your first quote. Even though the battery is fully charged, I would have expected that battery heating would start so that full propulsion power is kept available. I wasn't thinking that battery heating would continue the entire time the car is plugged in.

But I was also able to duplicate what you showed from your little test. I left the car unplugged all day and over night to cold soak the battery. When I opened the car to get in, the same battery heating message you described appeared when the car turned on. This to me was interesting, because the car was not plugged in. So battery heating does occur in the Model 3 even when it is not plugged in at least when the battery is fully charged. In my case, there was nearly 400km of range left in the battery. It would be nice if Tesla could clarify what battery SOC level the Model 3 is able to continue heating the battery when unplugged. And as you said, I was able to actually hear the motor actively heating, and once I plugged in, the sound coming from underneath where I would expect the motor to be increased. In my case, it took almost an hour of continuous battery heating before the cold battery status icons disappeared, and that was with climate control set to high about 15 minutes after battery heating started. Judging by the amount of time it took to rewarm the large mass of the battery, the pack temp must have been quite low in this case. But the cars behaviour and its ability to heat the battery appears different from what I observed mid December 2018. Presumably one of the updates I received since then has added improved functionality in this area. It would also be nice if Model 3 owners could access the battery heating function from inside the mobile app as a separate feature from cabin heating.

Full propulsion power isn't kept available when plugged in. You have to preheat or drive for that. The only time it heats when plugged in is when it expects to charge.

With your experience with the battery heating message, it probably started heating when you opened the door, in preparation for a drive. It wasn't sitting there keeping the battery warm the whole time.

 

[BrandonLive]

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.

I was more surprised that it actually got colder while charging and slowed down the charge rate, or at least that seemed to be what was happening.