# Preliminary trip efficiency: SR+ Model 3



## bwilson4web (Mar 4, 2019)

Using "Scan My Tesla" on our Mar 2019, SR+ Model 3, 15,541 mi, 2019.36.2.1, I measured the efficiency for an ad hoc, ~12 min., ~9.4 mi (~15 km) drive in town:

8.918 kW - "Battery power" average of all observations
7.874 kW - "R power" average of all observations
88.3% - "R power" / "Battery power" trip efficiency
These samples included everything regardless of speed. The more time stopped at a traffic light or slower speeds, the vehicle overhead reduces trip efficiency. A sunny day, no cabin or seat heating was needed. This was just a quick, trip efficiency metric and practice using the new tool.

Caution, "Scan My Tesla" is a sampling monitor which means care must be taken to not exceed the resolution and do a sanity check for data errors. For example, trying to calculate the shaft power using 'rpm' and 'torque' can give impossible shaft HP because the 'rpm' and 'torque' can come from different sample intervals. If two data points are reported in the same sample, it can _probably_ be used.

Bob Wilson


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## bwilson4web (Mar 4, 2019)

The scheduled pre-conditioning ended at 8:05 AM so I loaded the dogs at 8:27 and on the road at ~8:30 AM. By then, the "R Stator temp" was at 20 C while the outside temperature was 7 C, a difference of 13 C. Within 2 minutes, "R Stator temp" stabilized at 25 C. In addition of a comfortable cabin, the grid handled raising the "R Stator temp" 13 C.

Over the next few days, I'll try starting the car in the last 1-2 minutes of pre-conditioning to see what the starting temperatures will be.

Bob Wilson


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## bwilson4web (Mar 4, 2019)

The car has to be in gear, "D" or "R", to see all of the "scan my tesla" data points specific to your trim level. So I recorded the "All" table to make this list:

Time
Battery voltage
Battery current
Battery power
F power
R power
F torque
R torque
F torque 186
F RPM
R torque 108
R RPM
F Inverter PCB temp
F Inverter temp
F Stator temp
F heatsink temp
R Inverter PCB temp
R Inverter temp
R Stator temp
R heatsink temp
Max discharge power
Max regen power
Max pack voltage
Min pack voltage
Max discharge current
Max charge current
Max charge power
FL brake est
FR brake est
RL brake est
RR brake est
Steering Angle
Steering Speed
Accelerator Pedal
Brake Pedal
Consumption
DC Charge total
AC Charge total
DC Charge
AC Charge
Regen total
Drive total
Regenerated
Energy
Regen %
Odometer
Distance
Avg consumption
Nominal full pack
Nominal remaining
Expected remaining
Ideal remaining
To charge complete
Energy buffer
SOC
SOC UI
SOC Min
SOC Max
SOC Avg
Cell temp max
Cell temp mid
Cell temp min
Cell volt max
Cell volt mid
Cell volt min
Cell imbalance
Battery min temp
Battery inlet
Powertrain inlet
Outside temp
Outside temp filtered
Series/Parallel
Target PT ActiveCool
Target PT Passive
Target bat ActiveCool
Target bat Passive
Target bat ActiveHeat
Battery flow
Powertrain flow
Charge total
Discharge total
Discharge cycles
Charge cycles
Discharge
Charge
Stationary
Blower speed target
Evap enabled
Evap temp
Evap target
Duct left
Duct right
Heater left
Heater right
Cabin humidity
Cabin temp probe
Cabin temp mid
Cabin temp deep
12v battery volt
12v battery current
12v battery Amp hours
12v battery temp
Speed
0-50
0-60
0-100
0-130
0-160
0-200
60-100
80-120
Packets per second

A MacOS user, "AirDroid" is an excellent utility that creates a Web server on the Android. You can quickly navigate to the folder holding your files and download them onto the Macintosh. It shows an IP address and port that becomes the URL to access the web server, for example http://192.168.0.12:8888. Once opened, it becomes trivial to get the files moved to the MacOS system.

Bob Wilson


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## bwilson4web (Mar 4, 2019)

One of my interests is efficiency, OUTPUT / INPUT, expressed as an efficiency %. So I went to a favorite benchmark road, Brindley Mountain, a 1.1 mi (1.76 km), ~500 ft (~160 m), ~8% grade, South of Tennessee River, Route 231. Waiting for traffic to pass, pull onto the road and stop. Then floor the accelerator to climb the hill; turn around at the top, and; descend on cruise control.

*CHILL MODE*

Less 'frantic' driving, it still reaches the speed limit before anyone else at a light. So this is the first run:









Initially the car has reduced power to avoid spinning the tires. But around 60 kph (~37 mph) the full power is not available. Then the full power kicks in, ~140 kW (~188 hp).
Full power, climbing efficiency approaches ~98%.
To avoid a scary curve at the top, 180 kph (112 mph).
On the descent, the ~103% has a slight, ~1%, decrease in efficiency.

*STANDARD MODE*

Not used except for benchmarks, included here:









Peak power ~220 kW (~295 hp)
Peak velocity ~180 kph (112 mph) is also limited by the low banked curve at the top
Efficiency ~102% does not make sense unless there is a battery or traction motor power data problem
Descending efficiency, ~103% is about 1% less efficient than climbing suggesting the power efficiency is similar to chill mode
Bob Wilson


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## AlanSubie4Life (Nov 26, 2018)

bwilson4web said:


> Initially the car has reduced power to avoid spinning the tires.


That is not correct. You are confusing power and torque. You could be producing nearly zero power and spin the tires if there were enough torque.

Peak power on Model 3 is typically reached around 40-45mph. Then the torque starts to drop. Soon thereafter the power also starts to drop.


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## bwilson4web (Mar 4, 2019)

AlanSubie4Life said:


> That is not correct. You are confusing power and torque. You could be producing nearly zero power and spin the tires if there were enough torque.
> 
> Peak power on Model 3 is typically reached around 40-45mph. Then the torque starts to drop. Soon thereafter the power also starts to drop.


Here is the 'scan my tesla' data covering the first 10 seconds of chill mode, maximum acceleration up a hill:









140 kW (187.6 hp) - peak power happens at 6 seconds
72 kph (45 mph) - transition speed happens at 6 seconds
Bob Wilson

ps. A copy of CSV data in a ZIP file: http://hiwaay.net/~bzwilson/TSLA/chill.zip


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## AlanSubie4Life (Nov 26, 2018)

bwilson4web said:


> Here is the 'scan my tesla' data covering the first 10 seconds of chill mode, maximum acceleration up a hill:
> View attachment 31080
> 
> 
> ...


Exactly! Clearly shows that there is no power limiting going on at low speeds. This is chill mode so the max power limitation is totally artificial.

As I said, the statement: "Initially the car has reduced power to avoid spinning the tires" is completely incorrect. And you can see this in your plots. The torque (not plotted) is flat and reasonably constant all the way from 0mph up to 45mph. This is chill mode so that torque value is artificially capped, but obviously near zero mph the power output is nearly zero (power = torque * rpm).

It's more correct to say "the Model 3 in current form (even Performance model) produces insufficient *torque* to spin the wheels in a straight line on a dry, quality road surface."

There is no need to power limit to avoid spinning the tires - the car can't spin the tires in a straight line on a good surface. Not enough torque to the wheels.

If you could remove 400-500 pounds of interior trim and outfit the car with MXM4s, I think you might be able to spin the tires on a Performance Model 3. (But traction control would presumably limit that wheelspin.)


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## bwilson4web (Mar 4, 2019)

AlanSubie4Life said:


> Exactly! Clearly shows that there is no power limiting going on at low speeds. . . . .













seconds 0 -> ~12 kW which is lower than
seconds 1 -> ~40 kW which is lower than
seconds 2 -> ~65 kW which is lower than
seconds 3 -> ~88 kW which is lower than
seconds 4 -> ~108 kW which is lower than
seconds 5 -> ~125 kW which is lower than
seconds 6 -> ~140 kW which is the peak power that is held nearly constant for the rest of the acceleration
"Clearly shows that there *is* no power limiting going on at low speed." is exactly what the data graph shows.

Here is the Standard mode version:









seconds 0 -> ~25 kW which is lower than
seconds 1 -> ~75 kW which is lower than
seconds 2 -> ~125 kW which is lower than
seconds 3 -> ~180 kW which is lower than
seconds 4 -> ~210 kW, a local peak that tapers off for the rest of the acceleration
The facts and data show the power starts low and gradually increases to the peak power limited by Standard or Chill. If you don't see or understand, no problem, we'll just have to agree to disagree.

Bob Wilson


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## AlanSubie4Life (Nov 26, 2018)

bwilson4web said:


> The facts and data show the power starts low and gradually increases to the peak power limited by Standard or Chill. If you don't see or understand, no problem, we'll just have to agree to disagree.


Yes, it starts low but it is NOT _limited_. (By "limited", I mean per this definition: "the power could be higher but it's not allowed due to conditions/tires" - obviously power is not infinite, so it IS limited in that way.) That was my point. You said:



bwilson4web said:


> Initially the car has reduced power to avoid spinning the tires


This implies (to most people) due to the use of the word "avoid," that it is an action the car software or traction control takes AND that if the tires were stickier, you'd see more power output. *That's not the case. *_There is no "adjusting" going on - assuming no slip due to poor traction, the car just dumps the max allowed programmed torque and goes. _

In fact, the car goes ahead and rips out the maximum torque that is safe for the motor to handle (at least for the Performance model), nearly right away (after about 3-4mph). Power is just a consequence of how fast the wheels are spinning (so of course it ramps up as speed increases and torque stays constant). That's why it ramps up as you see. The only reason it is ramping is because the car is going faster.

By definition, power at speed zero is 0. That's true for any vehicle. Torque would have to be infinite for power to be anything other than close to zero at low speeds.

Even if Tesla decided they wanted to dump a lot more power and torque out (because they decided the motor could handle it) and allow sufficient torque to break traction, the power vs. wheel speed (assuming they didn't actually exceed the limits of traction) would look the same. It would start at zero and ramp up linearly as the vehicle accelerated. If the wheels were allowed to spin in place the motor would spin freely so very little torque would be required, even though rpm would be rising, so the power would still be low (power output would be sufficient to shred/smoke the tires but that is it).

In your second plot, you see exactly what I mentioned:


AlanSubie4Life said:


> Peak power on Model 3 is typically reached around 40-45mph. Then the torque starts to drop. Soon thereafter the power also starts to drop.


The torque starts to drop off at 65km/h, where peak power is reached, then power stays constant (because torque is dropping) until about 85km/h, whereupon power starts to drop.


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## bwilson4web (Mar 4, 2019)

AlanSubie4Life said:


> If the wheels were allowed to spin in place . . .


Hummm, looks like I need to repeat Chill and Standard with "slip-start" mode enabled. Regardless, the electrical power to the motor is 'volts * amps' which is independent of the 'rpm * torque' metric. It is one reason why the motor(s) can be used as resistance heaters in cold weather without 'tugging at the leash.'

Sad to say, I've upgraded to 2019.40.2.1 and there are postings about problems with some of the metrics. I'll have to run the four cases when we get a Standard day conditions. In North Alabama we typically see them at least 1-2 times in every 10 days.

Bob Wilson


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## AlanSubie4Life (Nov 26, 2018)

bwilson4web said:


> Hummm, looks like I need to repeat Chill and Standard with "slip-start" mode enabled.


You can try but slip-start will make no difference on a dry surface in a straight line. You can prove this to yourself by comparing your 60-0 stopping distance and time (about 125ft and less than 3 seconds) to your 0-60. Your vehicle produces nowhere near enough torque to the wheels to spin them. Even all seasons have considerable grip.



bwilson4web said:


> Regardless, the electrical power to the motor is 'volts * amps' which is independent of the 'rpm * torque' metric


Well, it's not independent in most cases. But sure there is a varying efficiency factor there. Mostly unrelated to the discussion except that it implies that the average current ramps up linearly with velocity on a run.


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## bwilson4web (Mar 4, 2019)

One of the subtle but important energy flows are coolant. In a perfect world, we would have the flow rate and both inlet and outlet temperatures. So in cool weather, 2-10 C (35-50 F), I've been looking at:









All but one of the coolant rate increases corresponds to jumps in R heatsink temp.
The typical 6.1 l/m flow carries 6.1 kW of heat per degree C.
The control laws appear to be focused more on limiting the middle temp electronics spikes versus the stator temp.
These were just local driving events around town and we're dealing with ordinary, waste heat. What I really need is the outside air temperature and the front radiator inlet and outlet temperatures. This measures the waste heat for all the systems.

Bob Wilson


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