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Demystifying the power consumers in my Model S

ZeeDoktor

Member
Dec 3, 2019
282
424
Sydney
I've been using a BT CAN bus adapter and the tesLAX app with some custom signals I've developed to shed some light on the various subsystem's energy consumption. Here's what I've found so far for my 2020 Model S Performance ("Raven").

The base energy consumption sitting in the car with gear in P and all energy consumers switched off or to minimum is 347 W. Aircon is off for all the tests.

Code:
Watts: Consumer:
38     Display at 100% brightness (instead of lowest)
79     Low beam headlights
121    Hi beams
33     Brake light
158    One seat heater level 3
125    One seat heater level 2
28     One seat heater level 1 (intermittent, switches off inbetween)
263    Rear window defog
28     Spotify play
23     Hazard lights
14     Dome lights
30     Front fog lights
5      Rear fog lights
303    Autopilot (seems to use the same amount regardless of whether TACC+AS or only TACC is engaged).

Then some tests to get air circulated in manual mode but with aircon/heater off:
40     Blower level 1
50     Blower level 2
60     Blower level 3
65     Blower level 4
90     Blower level 5
110    Blower level 6
140    Blower level 7
190    Blower level 8
240    Blower level 11 (note that levels 9-11 automatically engage recirculation so will be of no use when not used in conjunction with aircon/heater)
Energy consumption with the car off appears variable. I switched the car off and waited 5 minutes. There are still some fans audible, and some occasional relay clicking. The resulting energy consumption fluctuates between 120 - 200W in the off state. I haven't waited until the car is asleep, however, that figure can be estimated using e.g. teslafi.

Surprising learnings from this (for me):
- Playing music uses additional energy.
- Autosteer does not use additional energy. I would have though the servos for autosteer would consume additional energy.
- Seat heaters use interval heating, don't seem to have a permanent on position.
- lights use a lot less energy than I expected


When cruising on a highway doing 100 km/h, this translates into the following Wh/km consumption figures:
- 2 Wh/km when driving at night with high beams
- 3 Wh/km when driving with autopilot

Not that that's news, but any distance record attempts should be done during daylight hours and driving manually.
 
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ZeeDoktor

Member
Dec 3, 2019
282
424
Sydney
Aircon/heater uses up to 3kW of power in my tests. I suspect the music playing doesn't use more power because of network connectivity (it is connected all the time anyway) but due to the software running to decode/play the music itself.

I don't know about other Teslas, but mine has traffic aware cruise control (TACC) and Autosteer (AS). Combined they make the autopilot. In my tests it didn't matter whether only TACC was enabled or TACC+AS.

Using ludicrous+ mode (to heat the batteries so they can provide maximum discharge) uses 5kW of heating power. Depending on battery temperature, the available maximum power available varies drastically, from about 600hp with batteries at 26C, to 740hp with batteries at 50C. Yes, horsepower. Because that just means more when comparing against ICEheads. :)
 
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JZifch

Member
Oct 30, 2018
17
6
10591
Great analysis! I would guess that power usage on radio is affected by volume. Curious as to the difference between no volume, 50% volume, and 100% volume... I'm probably killing my range with my amp! Also curious about the heater's or A/C's affect on battery (and I would love to see the heat pump in model Y comparison!)
 

beatle

Active Member
Aug 31, 2019
1,273
741
Springfield, VA
I think the cabin heater uses up to 6kw. Not sure about aircon.

As for power output, check it at various SoCs. My car outputs in the low 500s when in the high 80% range, but power drops to below 400hp when under 20%.

I know you have a performance model, but I am curious to see if a LR+ could be faster than my car at a certain SoC threshold.
 

ZeeDoktor

Member
Dec 3, 2019
282
424
Sydney
My available hp varies from 240hp (at 0% SOC with yellow arc showing power limit on dash) to 789hp when fully charged and with batteries at 50C (in ludicrous+ mode). It depends on both SOC and battery temperature. At 50% SOC and 38C batteries, I have 665hp available.

Cell voltage drops the more power is drawn, that is what's causing the power limits at low SOC. When the battery voltage drops below 2.8V you can damage the cells, and the computers will run out of power...
 
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Dear Zee,

Do you have any data for Sentry Mode? My Model X seems to draw about 250 watts, continuous, when Sentry is on (based on the daily drop in remaining mileage indicated, about 20 miles/day). That can be a serious concern if the car's left parked for a week or more.

Any thoughts on how to minimize that -- without giving up Sentry, of course.

pax . Ctein
 

LarrySMN

New Member
Jan 17, 2020
1
0
St. Paul, MN
Does anyone have an estimate on what the impact is off running the windshield wipers are?
Of course when you run the windshield wipers, you are also probably running the Air Conditioner and the fans to defog the windows. some of the later information is listed above.

I think there may be an big impact. I noticed on a 200 mile trip, my wh/mi, went from 250 to over 300. I tried to keep the heat low, but had to run the windshield wipers, the defrost and the air-conditioning to dehumidify the air.

I noticed on a 20 mile trip later the same day that I dropped back to 250 wh/mi and did not run the windshield wipers or defrost.
 

Ostrichsak

Active Member
Sep 6, 2018
3,726
4,323
Colorado, USA
I suspect that there is a big difference between what is consumed when defrost is on “HI”, which is red/hot and when on low/cool or blue setting. The hi setting uses The 3kW stated above I imagine. But I am guessing the low setting uses much less.
In a round about sort of way I think you're right but it may not be for the reason you think. There really isn't a "high" and "low" per sey on the defrost option. I believe the red version uses heat whereas the blue version can use A/C in situations where there is fog/frost present but one doesn't want to use heat in conjunction with the defrost. So, being as the heat setting on the HVAC uses more energy than the A/C setting I believe this is why you are right but it's not the difference between a high or low energy use of the defrost itself. If that makes sense.
 

Pluturi

Member
Jun 15, 2020
138
150
Upstate NY
My available hp varies from 240hp (at 0% SOC with yellow arc showing power limit on dash) to 789hp when fully charged and with batteries at 50C (in ludicrous+ mode). It depends on both SOC and battery temperature. At 50% SOC and 38C batteries, I have 665hp available.
Curious on specific signals you are using to calculate this. I'm using ScanMyTesla and at 45C/70%SOC it is showing "front drive power max" of 387 and 535 for the "rear drive power max". I can't rationalize this to ~800hp unless there is some math or definitions I don't understand.
 

ZeeDoktor

Member
Dec 3, 2019
282
424
Sydney
@Pluturi max power available is a CAN signal available, it's in message 0x232 (MaxDischarge). That's reported in kW, simply multiply by 1.341 to obtain horses. When you demand all horses run, you can add the front and rear motor's available power for the total hp available to you. under normal driving conditions however you may have noticed that unless you exceed a significant power demand, the rear motor doesn't even work, it's all done with the front motor in our ravens.

@Ctein wipers use negligible power, without averaging total power used carefully I can't even see it when they're on. What you would have seen during your wet drive is increased resistance due to the water (aerodynamic drag gets appreciably worse with water over the surface of the car) and of course HVAC and (if used) rear window defog which I listed above.
 
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