The Limiting Factor - How the Tesla Semi “Broke the Laws of Physics”

[SwampNut]

This is one of those times where you are techically correct, but wrong in real world application.

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[Crissa]

Coasting to a stop requires you know where you are going to stop and how far out it is. Trying to scrub speed via coasting is tedious and the average driver will almost always get it wrong.

But that's the fun part of driving!

-Crissa

 

[Ogre]

But that's the fun part of driving!

Sure. I do wish Tesla would add back the option to turn off regen braking, but I think they don’t because it would end up left off in a lot of vehicles and reduce range. Then they have to field even more questions about range.

 

[BayouCityBob]

It won't have a clutched drivetrain to disable motors, to many parts and extra cost for a comparitively low load CT.

I think your speculation is wrong on this one. Clutched dual motor EVs which disengage the second motor are the typical set-up for most AWD vehicles these days. Just like the old P85 had it, now all the Magna drivetrains (Fisker, ArcFox) have this as do the VW systems for Porsche etc. Even the EV6 has a clutched second motor. I expect CT will have the same.

 

[Crissa]

Sure. I do wish Tesla would add back the option to turn off regen braking, but I think they don’t because it would end up left off in a lot of vehicles and reduce range. Then they have to field even more questions about range.

Lemme pushbutton it on. Put it on a scroll wheel. Put it on the brake pedal.

It is more efficient to drive that way, because I learned to drive stick. I know when to add and subtract resistance to a stop. It's how I ride a motorcycle.

It's the one thing that bums me out about a Tesla. The Least Common Denominator driving modes.

-Crissa

 

[SwampNut]

Wait, you can't disable regen any more? That's great, and I wish more car makers would remove that option. It's really stupid, and it leads to the frequent conversations I have with people who don't know about it, and don't realize what it saves in power and brake pads.

I've ridden motorcycles all my life, most have more deceleration from just chopping the throttle than regen does. It's just a learned way to drive. Even my neighbor's 85 year old father learned to love it in his X in just a couple days.

 

[Ogre]

Wait, you can't disable regen any more? That's great, and I wish more car makers would remove that option. It's really stupid, and it leads to the frequent conversations I have with people who don't know about it, and don't realize what it saves in power and brake pads.

I've ridden motorcycles all my life, most have more deceleration from just chopping the throttle than regen does. It's just a learned way to drive. Even my neighbor's 85 year old father learned to love it in his X in just a couple days.

Yeah, it’s never been an option to turn it off on my Y. I tried a few times on road trips so I could hypermile, but no luck.

It would be nice if it were an option that reset every time you started the car or something, but I don’t mind losing it either, the few advantages are trivial.

 

[SwampNut]

so I could hypermile

How would that let you save any energy?

 

[Crissa]

I've ridden motorcycles all my life, most have more deceleration from just chopping the throttle than regen does. It's just a learned way to drive. Even my neighbor's 85 year old father learned to love it in his X in just a couple days.

An Energica can be set to have heavier regen than you'd really want from motor drag. My Zero is pretty weak, yeah.

Regen can be super-strong. It's just how it's programmed and the recharge limit set on the battery. Honda hybrids can bring themselves to a hard stop just using regen x-x

But single-pedal has it set to low regen so it's not choppy. So you don't lock the wheels in the rain. Least Common Denominator driving mode.

How would that let you save any energy?

Because it's less energy loss to coast than to regen. You should only use regen when you need to slow down more than coasting.

Humans aren't very accurate in their inputs, so being able to coast or lower that variable, helps. Every time you use regen when you don't mean to, you're losing energy. A tiny percent in, a tiny percent back out.

-Crissa

 

[Ogre]

How would that let you save any energy?

Hyper miling you put energy into the car for a while then you coast for a while. The coasting parts use less zero energy so essentially half of the trip you are coasting and half of the trip you are burning 20% more energy than normal.

It’s one of those things which sounds like nonsense when described, but actually works. Its a bit of a a pain in the ass to do correctly, particularly when you car doesn’t have a true “Coast” mode.

 

[SwampNut]

Turning on AP or cruise would likely use less energy than coasting.

 

[Ogre]

Turning on AP or cruise would likely use less energy than coasting.

I know… it sounds ridiculous, but hypermiling works. All of the long distance driving/ mileage records use some hypermiling.

But its super annoying in traffic.

 

[Crissa]

Pass, change back, coast, pass, change back, coast...

I don't do it In traffic, tho.

And yes, cruise control is better than a human trying to balance a speed. But a hyper-miler... well, you use the cruise control to hold power levels if you're smart.

Practically, being able to vary regen to manage your speed is as important as being able to vary the power to manage your speed.

-Crissa

 

[Sirfun]

Lemme pushbutton it on. Put it on a scroll wheel. Put it on the brake pedal.

It is more efficient to drive that way, because I learned to drive stick. I know when to add and subtract resistance to a stop. It's how I ride a motorcycle.

It's the one thing that bums me out about a Tesla. The Least Common Denominator driving modes.

-Crissa

Just imagine how good a car with super low drag and lots of weight, like a Tesla, would coast!!!

 

[SwampNut]

I know… it sounds ridiculous, but hypermiling works. All of the long distance driving/ mileage records use some hypermiling.

I fully understand it and agree. Nobody has explained why they think it would work in a Tesla, and I'm pretty sure it won't.

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