Shore power usage during morning warmup

[eprosenx]

I thought this data might be interesting to some on the forums.

I was on vacation for over a week and so my M3 sat in my driveway unused. I normally charge to 80%, but I had set it to only maintain 50% while gone. Yesterday on my flight home I set it back to 80%, so yesterday afternoon it charged back to 80% (but I did not use it at all that day).

This morning I fired up my cabin heating before leaving the house resulting in the following power draw: (I do not remember if it showed any icon in the app to indicate if battery heating was happening) . This graph is from my Sense Energy Monitor (shows whole house draw - yellow is solar production so ignore that)

I have a 60a circuit (48a continuous) into my Wall Connector. I have a M3 LR. The car was fully cold soaked this AM after over a week of not being touched. The app said it was 31f in the cabin when I told it to warm up (frosty morning).

Note that my gas furnace I think was running at the start of this graph (about 1000 watts) and I suspect it stopped during the car charging interval.

I got the "regen limited" warning when I fired up the car and the dots that show the reduction. I drove my 15 miles to work and I think I still had more dots than usual (they eventually all go away right?). Regen worked to some degree though (it was not as noticeable as charging to 100% where you get no regen - though maybe that was because it did pre-heat the battery a bit)

I think the interesting bits here are that it seems to nearly max my charger (11.5kw) just doing warmup (presumably none of this was going to battery charging). I wonder how much (if any of this?) was going to battery warmup vs. just cabin heating?

Presumably the load stopped when I unhooked the car to drive to work.

I really want more diagnostic data about what is happening under the hood! What is the battery temp? How much heating is being done to the battery? How much heating is being done in the cabin?

 

[smatthew]

as a data geek I also wish I could see the behind-the-scenes data on my model3

 

[Kermee]

Yeah. I know of several people trying to access CAN, but last time I researched, it was still very much a WIP.

There was a video last month where someone tried to determine how much the cabin heater would max out at: How much power does the Tesla Model 3 heat system draw?

His method showed 20A. Which is coming awfully close to 5kW of power. As for where the rest of the 6.5kW in your graph is going... Not so sure?

 

[eprosenx]

Yeah. I know of several people trying to access CAN, but last time I researched, it was still very much a WIP.

There was a video last month where someone tried to determine how much the cabin heater would max out at: How much power does the Tesla Model 3 heat system draw?

His method showed 20A. Which is coming awfully close to 5kW of power. As for where the rest of the 6.5kW in your graph is going... Not so sure?

Exactly!!! I was wondering if the rest of that power was going into battery warmup (perhaps for the first time ever).

I wish I had looked more carefully at the app this AM to see if it indicated battery warming and also looked at the amperage draw on the display when I got in the car (but before disconnecting it).

Maybe tomorrow I will have more time to check it out.

 

[Big Earl]

Battery heat is up to 4 kW (read it somewhere authoritative, can't find the link) and cabin heat is up to 6 kW. The vehicle may have started charging when OP initiated preconditioning, which would explain the additional energy consumption.

 

[eprosenx]

Here is this mornings warmup. It was not as cold. Tesla app said cabin was 42F.

I am not sure if it timed out and stopped cabin heating before I went out to the car, or the falloff at the end is due to me unplugging the car (it was right around that time).

Regardless, I don't think I got any "regen limited" warnings when I got in the car.

Perhaps that first big spike is the battery heater + cabin heater, and then the big falloff is the battery heater kicking off but the cabin heat continuing?

Not sure what the even larger spike is just for the first few minutes of charging.

 

[Big Earl]

In the case of the cabin heating, PTC heaters typically start at full power and then ramp down some as the element warms up (they're self-regulating), followed by a further ramp down as the system approaches the setpoint. The battery heater is all controlled by the drive inverter and it has variable output. It would make sense that it would start off at a higher power and ramp down some as the battery approaches the temperature setpoint.

It would be helpful if you could monitor your app during the morning warmup and identify at what point the cabin gets up to temperature.

I'll try to get some measurements on our JuiceBox on Saturday and we can compare notes.

 

[eprosenx]

In the case of the cabin heating, PTC heaters typically start at full power and then ramp down some as the element warms up (they're self-regulating), followed by a further ramp down as the system approaches the setpoint. The battery heater is all controlled by the drive inverter and it has variable output. It would make sense that it would start off at a higher power and ramp down some as the battery approaches the temperature setpoint.

It would be helpful if you could monitor your app during the morning warmup and identify at what point the cabin gets up to temperature.

I'll try to get some measurements on our JuiceBox on Saturday and we can compare notes.

I have been swamped the last couple weeks at work and I have not had a chance to run this test as you describe. I think it would be a fascinating test. (it also has not been as cold)

I did however tell the car to pre-warm as I got in the shower, but then I ended up having to take a conference call and so the car ran for longer than I was planning for.

Interesting the large spike to begin with but that was very brief. Then it ramped down as presumably the cabin warmed, and finally a steady state for quite a while of what I am guessing is just keeping the car warm? (or it could be battery heating too?)

I think it may have been like 54 Fahrenheit this morning in the cabin when I turned it on (don't quote me on that). I had full regen ability when I finally got in the car (no dots on the bar).

I am super happy to have a Wall Connector with a 60a circuit. I never worry about charging speed EVER. And I know I can warm up the car in the AM without draining the battery at all. I love it!

 

[Chiwahwah]

1.

as a data geek I also wish I could see the behind-the-scenes data on my model3

smatthew.....have you looked at Teslifi or Teslaspy? Lots of data reporting with either of those services. There is a thread comparing the two in this forum.

2. I’m a new M3 owner, but after a lot of reading, I was under the impression that the M3 did not have a dedicated battery warmer like the S and X have. When you all talk about power going to the battery warmer, are you referring to an actual battery warmer or merely the power going into the battery and therefore warming it?

 

[eprosenx]

1.


smatthew.....have you looked at Teslifi or Teslaspy? Lots of data reporting with either of those services. There is a thread comparing the two in this forum.

2. I’m a new M3 owner, but after a lot of reading, I was under the impression that the M3 did not have a dedicated battery warmer like the S and X have. When you all talk about power going to the battery warmer, are you referring to an actual battery warmer or merely the power going into the battery and therefore warming it?

The model 3 has a way to send current into the motor in a way that does not produce torque. So effectively they can use the motor as a heating element and then the cooling system moves that heat into the battery.

 

[AlanSubie4Life]

@eprosenx:

This checks out - I have a Chargepoint in the garage at work and did some experiments with steady state draw. Chargepoint lets you monitor kW draw for a charging session real time.

~60 degrees ambient in the parking garage. No solar heating. All this data taken after an hour or more of prewarming, to eliminate any cold battery issues (I had some regen dots early on).

Climate control set to 71: 2kW steady state draw from Chargepoint (due to AC->DC on-board charger losses the actual power the car would need if it weren't plugged in is somewhat less I assume - maybe 90% of this?)

Climate control set to 73: 2.2kW

Climate control set to 80: 3kW

Climate set to 68: 1kW

Seems to align pretty well with your steady-state data.

Obviously the more frightful the weather the higher the steady-state consumption will be. But inside will be delightful.

 

[smatthew]

smatthew.....have you looked at Teslifi or Teslaspy? Lots of data reporting with either of those services. There is a thread comparing the two in this forum.

I'm a TeslaFi subscriber. Use my member name for a free month!

It's interesting watching the TeslaFi data fluctuate when charging. I have my Tesla3 set to charge at 5:00AM. It seems like lately about 1kWh of power is dissipated in the first few minutes of charging. I.E. "Used: 1.8kWh; Added: 0.9kWh" This AM when I left for work around 6:00 AM it still showed a 1.1 kWh discrepancy between used and added.

The main thing I wish TeslaFi could show is Autopilot usage. Secondary would be AutoPilot disengagements. But neither of those data points are in the Tesla API.