Flat towing the Cybertruck, "It's a giant battery for my RV", etc

[JBee]

I don't know, I just know they don't want to do it for long.

There's ways to create dummy loads, shorts, electrical disconnects, and, like on the Semi, an actual clutch. So there's ways to do it. Dummy loads and shorts still create heat and potential, and while you as a driver would be aware if something went wrong in the drive system, someone towing wouldn't.

-Crissa

It really depends on the motor and drivetrain used, even with Tesla they are not all the same.

For example towing a RWD M3 will work without modification, simply because it has an induction motor that doesn't have a permanent magnetic field like a Permanent magnet motor with rare earth metal magnets. This is because an induction motor "induces" a magnetic field using a field controller circuit that can be modulated between a full or no magnetic field. No field equals no power flow. A permanent motor on the other hand, especially high performance versions always have a strong magnetic field from the permanent magnets. They can not be switched off, so to coast you either have to regen or accelerate, and is likely why Tesla switched these to one pedal driving by default. The M3 and MY Dual motors already completely switch off the rear induction motor like this when they cruise or coast, without using a clutch etc, as the front PM motor on them produces the best efficiency for cruise and regen and is a lower power level, and can't be switched off, so it only uses that most of the time. The induction motor is just there for boost essentially, with the PM motor constantly driving or regening off the front wheels.

You must also consider the fact that not all motors perform the same under load and at certain rpm. They are all variables that need to be considered when selecting the gear ratio in reference to the motor efficiency and performance heat map.

Now with the latest proposed "next-gen" motor, they are claiming it has "no" rare earth metals. This either means they have found a novel material to magnetise instead for their PM motors, or more likely, they are simply using an upgraded but cheaper induction motor for it, like they use in the RWD models. Using a CF wrapped induction motor might just be the best version of induction yet, as you get a higher power density, but smaller form factor by being able to get closer rotor clearances at higher rpms. All from a rotor that can't expand through the CF band holding it together, which all in turn reduces flux losses that needs to be extracted as heat. Which also means it has better short term peak performance before overheating.

I'm sort of half expecting the new M3 highlander to have these drive units already, as in the last slide show they had these next gen drivetrain assemblies, with speed controller only cost some $1000 all up. Previously Monroe quotes the Plaid motor alone at $460ea. If they are cheaper and more efficient, you will get more range at lower cost with no extra batteries required, so why not use them if they are ready to go? Alternatively the simpler and safer manufacturing of induction motors , in comparison to more expensive PM ones, let alone "rare earth cost free", means they would even have some change left to put some more batteries in instead.

You can read more about this from Tesla themselves:
https://www.tesla.com/blog/induction-versus-dc-brushless-motors

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[HaulingAss]

I don't know, I just know they don't want to do it for long.

There's ways to create dummy loads, shorts, electrical disconnects, and, like on the Semi, an actual clutch. So there's ways to do it. Dummy loads and shorts still create heat and potential, and while you as a driver would be aware if something went wrong in the drive system, someone towing wouldn't.

-Crissa

Because there is no regen braking felt during these conditions, I assume the motor is being fed with just enough current to overcome the normal drag of the motors, even when the throttle pedal is fully released. I think the same thing happens if I select "Neutral" with the "gear" selector.

And this is why the highest efficiencies are obtained from drivers with steady throttle control, wavering between "neutral" and throttle lightly on is not as efficient as maintaining a light throttle at all times. Of course, wavering between light regen and throttle on is worse.

I mention this because people seem to put a lot of trust into "real world ranges" when, in fact, the results are highly dependent upon what the tester wants to see.

 

[anionic1]

Greetings,

With a 9kW ground mount solar array going up adjacent to my new RV cover so time to ask:

1) Any idea if I can 'flat tow" (ie, w/o trailer) a Cybertruck?

2) The flat tow question relates to possibly getting a motorhome with a diesel genset (always handy) with a separate fuel tank that I could fill w/ off road if needed for SHTF, as above.

3) Already had an electrician go over my RV bumper pull and easy to run a circuit to not even have to unhook camper, but plug into 50A at campground and charge CT when trailer is plugged in. A state park campground will cost about $12-20 for 50A and, if my math doesn't suck (it does) would yield about $33 worth of electricity at $0.133/kWh

4) Great appeal of CT is that with 200 kW of battery, if truck were charged I'd be good to go off grid for a while if SHTF and that battery capacity, if installed into the RV, (forget the weight) would be about $40k USD by itself. (See above math disclaimer)

PV array is like this but two panels wider, 28 in all.

Any and all thoughts most welcome, as always

JR

What does the PV array have to do with off grid camping? And 9kW is small for an EV. 200/9 is about 24 hours of solar to fully charge the CT or about 4 days of good sunlight

 

[MrMoparMan]

So what do you guys think about Rivian just having anounced that the dual motor will be flat towable? (conversation with Munro and RJ Scaringe)

I know Munro said it could, but they only seemed to talk about the rear motor decoupling?
I have been hoping the CT will use the decouplers from the Tesla Semi to allow flat towing.

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