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How long is too long to leave heat running while charging?

Suzie

New Member
Oct 30, 2019
3
0
Canada
I live in Canada where average morning temps will be - 30 for about a month soon.

Started using Teslafi, cool program, I can set my car to start heating up at 6:30, it uses a bit of battery and by 7:15 (in - 5, haven't tested - 30 yet) the car is warm and fully charged.

Does anyone know how bad it would be to have it run for two hours sometimes? I don't always wake up the same time, but this time allows me to have it warm as early as I would likely need. Today it was running for 2 hours before I got up, it seems fine, I just am skeptical that it could be bad for it if I do it all winter.
 

Rockster

Active Member
Oct 22, 2013
3,014
4,692
McKinney, TX
It's really no different than using the heater while driving. Would you be concerned for your heater if your commute totaled two additional hours per day than it currently does? I'm guessing you wouldn't give that a second thought.

The benefit here, too, is that you're using shore power instead of battery during the preheating period.
 

BZM3

Member
Aug 15, 2019
281
183
Somewhere
I live in Canada where average morning temps will be - 30 for about a month soon.

Started using Teslafi, cool program, I can set my car to start heating up at 6:30, it uses a bit of battery and by 7:15 (in - 5, haven't tested - 30 yet) the car is warm and fully charged.

Does anyone know how bad it would be to have it run for two hours sometimes? I don't always wake up the same time, but this time allows me to have it warm as early as I would likely need. Today it was running for 2 hours before I got up, it seems fine, I just am skeptical that it could be bad for it if I do it all winter.
zero bad.
 

doghousePVD

My grandfather’s car
Dec 3, 2018
648
597
New England, USA
I find it takes a lot more than an hour to warm up the battery in really cold weather. I park outside.

I assume (hope) you have shore power to do this, and not wasting your battery.
 

Suzie

New Member
Oct 30, 2019
3
0
Canada
It's really no different than using the heater while driving. Would you be concerned for your heater if your commute totaled two additional hours per day than it currently does? I'm guessing you wouldn't give that a second thought.

The benefit here, too, is that you're using shore power instead of battery during the preheating period.

Right! That's exactly what I was thinking, and that's a good point I wouldn't think twice if I was driving that long. I really want to be a good as possible to the battery in the cold, I think I'm on the tight track.
Thanks everyone!
 

Suzie

New Member
Oct 30, 2019
3
0
Canada
I find it takes a lot more than an hour to warm up the battery in really cold weather. I park outside.

I assume (hope) you have shore power to do this, and not wasting your battery.
Yes I do, and thanks, I have been noticing heating it is a bit slower than I expected. It seems like -30 would need 1.5 hours anyways! Not that I should be surprised
 

duanra

Active Member
Dec 14, 2018
1,310
810
Montreal
Charging the battery will do the trick. According to my experience with a real cold battery, it will take the battery up to 45 minutes to warm up by charging it with a level 2. (Cold Montreal morning).
 
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gavine

Petrol Head turned EV Enthusiast
Apr 1, 2014
2,610
2,171
Philadelphia, PA
The new "scheduled charging" feature coming-out will help with this. It'll automatically start charging when it needs to in order to be complete by the set time (your departure time). Assuming you're using a level-2 connector, the charging-itself will warm-up the battery and the car will turn-on the HVAC in time automatically as well.
 

jerry33

(S85-3/2/13 traded in) X LR: F2611##-3/27/20
Supporting Member
Mar 8, 2012
19,997
24,660
Texas
No reason why it should be bad. When camping at an RV park, I leave the heat or A/C on all night. Works just fine. For most electronic items (including batteries) the rule of thumb is "if you are comfortable, then your electronics are comfortable".
 
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justsomeguy

Member
Jul 4, 2019
295
292
Vancouver, Bc
Charging the battery will do the trick. According to my experience with a real cold battery, it will take the battery up to 45 minutes to warm up by charging it with a level 2. (Cold Montreal morning).
The car will use the motors to heat up the battery in this scenario. At -1C my cold soaked car spent ~12 minutes charging at 0km/h but drawing the full [email protected]
 
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gavine

Petrol Head turned EV Enthusiast
Apr 1, 2014
2,610
2,171
Philadelphia, PA
It is not the motors that are being used as heaters. It is the transistors in the inverters (which are located within the motor assembly).

To precondition the battery, my Model 3 makes different sounds when I'm navigating to a Supercharger with a cold battery. It only does it at lower speeds, presumably because the motor/inverter generates enough heat under higher loads without artificially taxing it. Even regen sounds different in that scenario and you can see the power draw doing this on the power-meter bar when stopped.

The first time this happened, I thought something was wrong until if finally dawned on me. Perhaps that's why, under V10, the car now shows a message on the screen telling you when it is preconditioning the battery.
 

Darmie

Super Member
Supporting Member
Jan 13, 2016
2,055
1,360
Clear Lake TX.
There are other options. you can place an NFC chip near your bathroom sink or any place to just lay down the phone to start the heating.

 

ajdelange

Active Member
Dec 10, 2018
1,077
638
Virginia/Quebec
Do you have the literature for this? I've never seen an actual technical breakdown for how it works.
No, of course not. You might find a patent filing but that's about as far as Tesla goes on public documentation. You can gain access to the service manuals for $3000 a month or something like that but otherwise its furphies all around.

It's pretty obvious how it would work, however as the inverter is a 3 phase (3 leg) H-bridge. In full disclosure note that this is surmise too based on modern electrical vehicle motor control practice. Each leg contains a pair of transistors in series with the midpoint going to one winding of the motor. Turn one + connected transistor on at the same time as the two - connected transistors in the other two legs and you get current flow into one stator winding and out the other resulting in a magnetic field in a particular direction. Now switch on a different + connected transistor and its complementary - connected transistors on and the magnetic field rotates 60 °. This is how the motor works. The transistors switch from full off (very high impedance) to full on (very low impedance) as fast as possible in order that as little heat as possible is generated as heat is wasted energy.

Now instead of gating the transistors between full off and full on suppose we gate them ALL half way on. They all draw moderate current and as they are all on no current flows in the motor windings. They become resistive heaters.
 
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Reactions: justsomeguy

justsomeguy

Member
Jul 4, 2019
295
292
Vancouver, Bc
No, of course not. You might find a patent filing but that's about as far as Tesla goes on public documentation. You can gain access to the service manuals for $3000 a month or something like that but otherwise its furphies all around.

It's pretty obvious how it would work, however as the inverter is a 3 phase (3 leg) H-bridge. In full disclosure note that this is surmise too based on modern electrical vehicle motor control practice. Each leg contains a pair of transistors in series with the midpoint going to one winding of the motor. Turn one + connected transistor on at the same time as the two - connected transistors in the other two legs and you get current flow into one stator winding and out the other resulting in a magnetic field in a particular direction. Now switch on a different + connected transistor and its complementary - connected transistors on and the magnetic field rotates 60 °. This is how the motor works. The transistors switch from full off (very high impedance) to full on (very low impedance) as fast as possible in order that as little heat as possible is generated as heat is wasted energy.

Now instead of gating the transistors between full off and full on suppose we gate them ALL half way on. They all draw moderate current and as they are all on no current flows in the motor windings. They become resistive heaters.
Thanks. Appreciate the info.
 

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