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Morning warmup taking battery power while plugged in.

Darthbenji

Active Member
Mar 27, 2018
1,003
594
Ontario
Anyone else have this. Car is charged to 85%. Tune in climate for 20-30 minutes before leaving. When I get in the car the battery is at 81-82% even though it’s plugged in.
 
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ZappCatt

Member
Nov 2, 2019
320
263
Santa Clara
Mine does not drop that far, but when I turn on Climate to warm up the car(Northern California, so 40-50 degrees out) my charge typically shows "5 mins to full charge" no matter how long I have it going. That means(to me) that everything that I have on is pulling more than my 32a 240 circuit is putting into the car. I imagine in a real winter climate, this could lead to a larger deficit, thus causing the significant 3-4% drop in the battery level.
 

ZOMGVTEK

Member
May 19, 2015
558
433
'Merica
The car has no way to directly run off the wall power, and its limited by the capacity of the circuit its connected to. Preheating consumes around 12-13kW if its warming the battery as well as the cabin with the dual motor, so even if you have a 48A/240V wall connector the car can barely maintain its current state of charge until the heating power drops as the cabin warms. The chargers output just goes to the battery, and the car has no active intelligence or way to independently run off the wall power. It could throttle the preheat power to match incoming power, but Tesla appears to have skipped this method since it would lead to very slow preheating in some cases. So this just means for lower power charger connections you will consume energy off the battery while preheating.

Whats your charger power?
 
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WilliamG

Active Member
Apr 20, 2019
3,024
2,919
Seattle, WA
The car has no way to directly run off the wall power, and its limited by the capacity of the circuit its connected to. Preheating consumes around 12-13kW if its warming the battery as well as the cabin with the dual motor, so even if you have a 48A/240V wall connector the car can barely maintain its current state of charge until the heating power drops as the cabin warms. The chargers output just goes to the battery, and the car has no active intelligence or way to independently run off the wall power. It could throttle the preheat power to match incoming power, but Tesla appears to have skipped this method since it would lead to very slow preheating in some cases. So this just means for lower power charger connections you will consume energy off the battery while preheating.

Whats your charger power?

12-13kW? Source? Never heard it being that high.
 
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Darthbenji

Active Member
Mar 27, 2018
1,003
594
Ontario
So is there any difference then between turning on climate plugged in or unplugged? If I’m heating the cabin there’s not enough power left to replenish the lost charge.
 
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ZOMGVTEK

Member
May 19, 2015
558
433
'Merica
Since V10, the car now aggressively heats the battery while preheating and its a bit chilly. I’m extrapolating a bit here, given I know the input power to the wall connector is is ~11kW and the SOC drops anyways, the vehicles consumption is presumably beyond the rated 10.5kW charge power. The motors are audibly heating the battery, and data shows the motors tend to consume 6.5kW when heating. Tack on the ~5kW for the heater running full tilt, the blower motor, defroster, seat heaters, and assorted body electronics should put it in the 12-13kW range for a ‘worst case’ when the cabin is cold enough that the heater sustained full power.

For a single motor car, the peak power should be more like 8.5-9kW. Assuming the car has 32A/240V available, it’s going to dump maybe 7.2kW into the pack, which tends to be less than 8.5, so it won’t be able to sustain charge if the battery is being heated. You can tell it’s heating the battery if you listen near the rear of the car while it’s preheating and you hear a somewhat loud pump sound coming from the rear drive unit. It stops when you open a door if the vehicle is unplugged. It will continue preheating even if you open a door with it plugged in. And of course it will only draw a little bit off the battery when plugged into the wall, so it’s still better it’s plugged in if available. Eventually the heater power will start to taper and the car does charge back up. But this might take more than the 30 minutes the car will preheat for depending on conditions.

One other aspect that may be a factor, is the indicated SOC may change as the battery warms up. I’m not sure though.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,280
11,087
San Diego
12-13kW? Source? Never heard it being that high.

It is chilly in Seattle right now. I assume you have 40 or 48A charging...if you do....Even without engaging battery heaters, leave your car outside, let it chill, plug it in, set charge limit below current charge level, set heat to max, turn on AC, and leave a door open. You should see that alone reach or exceed 40A. 9.6kW. And then as mentioned battery heating from the motors can go on top of that. Could easily see it drawing down the battery briefly (obviously if not set to max the heat use will back off a fair amount as the cabin warms) even with 11.5kW charging.
 

rrolsbe

Member
Feb 18, 2017
219
124
Albuquerque
I thought the Scan My Tesla app indicated the maximum cabin heater draw was between 6 and 7KW. If the HVAC is set to AUTO, I guess the AC can cycle on and off while heating the cabin. Does the AC drawn 2.6KW or more?
 

TomB985

Member
Apr 15, 2019
441
516
Isanti, MN
From what I understand, this is the heater core our cars use:

https://cdn.borgwarner.com/docs/def...ct-sheet-hv-air-heater.pdf?sfvrsn=61d4b13c_18

Meaning the maximum resistive heating load is 6.7 kW, plus the additional load for powering the associated electronics and blower motor. Very interested in more details regarding battery preheating… I read a lot when I first got the car back in April and the consensus was that the battery had no preheating function. Sounds like that has changed, does anyone have more details?
 

rrolsbe

Member
Feb 18, 2017
219
124
Albuquerque
@TomB985

Thanks for the link! I like you have done a LOT of reading. From what I had read in the past, the traction motor was not used for heating the traction battery while parked unless the car was plugged in an active charging session; likewise, the battery was only heated to a level required to charge at the delivered power level. For example I charge at [email protected] and the motor stops heating the battery at around 54F. Need to verify if the traction battery is now heated while pre-conditioning the cabin , when not actively charging, and to what cell temp. It was my understanding that the car would not heat or cool the traction battery with temps below -22F or above 140F unless the car was actively charging or being driven, maybe that has changed or maybe it should to protect the battery?
 

WilliamG

Active Member
Apr 20, 2019
3,024
2,919
Seattle, WA
It is chilly in Seattle right now. I assume you have 40 or 48A charging...if you do....Even without engaging battery heaters, leave your car outside, let it chill, plug it in, set charge limit below current charge level, set heat to max, turn on AC, and leave a door open. You should see that alone reach or exceed 40A. 9.6kW. And then as mentioned battery heating from the motors can go on top of that. Could easily see it drawing down the battery briefly (obviously if not set to max the heat use will back off a fair amount as the cabin warms) even with 11.5kW charging.

I have 48A charging. Never seen my battery drop while pre-conditioning in my garage.
 

AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,280
11,087
San Diego
I have 48A charging. Never seen my battery drop while pre-conditioning in my garage.

You are in a garage. And 11.5kW would make it really rare, especially in a mild climate like Seattle.

In any case it is super easy to figure out the maximum AC values for these things using the procedure above. You can even get an idea of battery preheating load if it is cold enough, I suppose, though could not separate it from the heater core use.

I have no problem getting the load up to 40A (9.6 kW) in San Diego and definitely no battery heating in that number. I have only 40A so I can’t explore above that.
 
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AlanSubie4Life

Efficiency Obsessed Member
Oct 22, 2018
9,280
11,087
San Diego
unless the car was actively charging or being driven, maybe that has changed or maybe it should to protect the battery?

If you can tolerate watching the video, Björn has done some videos recently of this showing the CAN bus power draw for the stator heating. I have not watched them but apparently for AWD it is something like 7-8kW total.
 
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Sophias_dad

Supporting Member
Jul 29, 2018
1,006
872
Massachusetts
Have you actually checked that at the start of that heating period your car is at 85%? If I charge my car to 90% and leave it plugged in, it'll drift considerably lower(not 3% lower) before it decides to charge again. Maybe yours starts out that heating period well below your 85% setpoint, or the perceived 85% has gone down just due to the battery cooling off.
 

Darthbenji

Active Member
Mar 27, 2018
1,003
594
Ontario
Yep. Open the app. Check soc. Turn on climate for 20 minutes or so and when I leave the soc has dropped. It’s as if it wasn’t plugged in at all.
It’s the same behaviour as when I leave my office where I can’t plug in.
 

rdunniii

Member
Jun 27, 2012
257
133
Reno NV
Has anyone noticed this? I have departure time charging set for 11:30. Of course it did it's charging to complete at 6AM as usual. BUT, now sitting here at the computer the charging system is clicking on and off in the garage as the climate system has now kicked in for the 11:30 departure and it is indeed charging at 10kW; intermittently. Oh, 50.7.
 

Tron 3

Member
Nov 1, 2018
199
281
Colorado
I have my LR AWD set to charge at midnight because the rate is lower. By the time I leave the charge cycle is complete, and it is my impression that since the charge has been completed it won't charge again until midnight - so when I warm the interior, even though it is plugged in the car uses the battery only.
I haven't tried setting a departure time.
 

TomB985

Member
Apr 15, 2019
441
516
Isanti, MN
Unless this is changed very recently, mine will suck power from the wall when preheating the cabin while plugged in regardless of time of day or schedule charging. I don't plug mine until after 8 PM Monday through Friday because of this… My 7.3 cents off-peak rate jumps to $0.45 during peak hours. I'm liable to forget and pay through the nose for preheating the cabin during those hours.
 
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