M3 towing an Airstream video

[Cyber Larry]

So, need to unhook the trailer to get to the charger.... each time.

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[Crissa]

So, need to unhook the trailer to get to the charger.... each time.

The charger isn't blocked by the trailer. There's just not alot of places to park at most chargers yet. Maybe eventually we'll have pull-through chargers. They're becoming more common in Northern Europe.

-Crissa

 

[ldjessee]

I would think that the M3 can handle 100%. But since the graph hits a limit, we cannot be sure if the M3 is not outputting over 100%.

In the military, it is very common to have 100% setting, then a 125% emergency power setting for engines (turbine, electrical, hydraulic pumps). These are meant for short, brief periods where it is better to do long term damage to the engine/motor than suffer short results of not having that extra power.

But I have been wrong before and could be wrong here. Just given the engineering focus and safety, making the cooling system able to handle a 100% duty load continuous makes sense... but if other conditions are stressing the system (ie, ambient temps are over 100 degrees, high altitude, etc), then maybe it would not be able to handle 100% output for an extended period.

It would be interesting to see someone take an M3 powertrain and test it to failure to see exactly how much it can take...

I expect to see someone do that to a Cybertruck, especially if it is to be adopted by a military... which, if I was looking at the options of a military truck/scouting vehicle, the Cybertruck would already meet many criteria...

 

[ajdelange]

Also, in the part of the video where they show the power graph, it looks to be maxed out quite a bit of the time. How long can an M3 Tesla run at maximum output before things start to overheat? I cannot imagine the system is designed for 100% duty cycle at max output at max ambient temp. An electric vehicle with more total power like the CT would hopefully give more "headroom" of not being maxed out as much.

The top of the graph is the maximum consumption rate that the graph is designed to display. This appears to be about 600 Wh/km which is apparently well over twice the rated consumption for this car (hard to read the rated from the jiggly video but looks like about 160 Wh/km = 256 Wh/mi?). This is not a power graph. It is an energy consumption graph. The power meter is separate. The maximum power is drawn when the vehicle is going up hill and accelerating at high speed. An electric motor's torque vs speed curve is flat at low speed and then declines approximately linearly with speed above a break point which is at the maximum torque - maximum power point. Above that break point power is limited. Below it torque is limited. Towing a trailer at high speed one is not in the power limited region until one accelerates to the point where it is impossible to go any faster. Thus these guys never reached the maximum power output of the car.

But the question remains "Which motor will last longer - one that operates at 50% of its maximum power rating or one that operates at 80% of its maximum power rating?" I think the answer is probably obvious.

 

[Crissa]

A Model 3 consumes rather alot less than 300Wh/km, ajdelange.

-Crissa

 

[ajdelange]

Thinking about this a bit more: the video shows them chugging along at about 110 kmph which at consumption of 600 Wh/km means 66 kW = 88.5 hp being delivered by the motors. As the meter is pinned the actual power is clearly more than this. Assuming the car weighs 4500 lbs and does 0 - 60 in 5 seconds that means its motors are capable of 394 hp. Thus the motors are delivering only 22% of their maximum power (plus whatever is clipped by the graph).