Model 3 AWD / Performance - lower UDDS Range!

[voip-ninja]

I think this probably explains why Tesla sandbagged the range numbers on the Model 3 LR RWD.... They can claim same range across the whole Model 3 LR family by using the 8% lower value for the AWD.

 

[jfrieden]

I think this probably explains why Tesla sandbagged the range numbers on the Model 3 LR RWD.... They can claim same range across the whole Model 3 LR family by using the 8% lower value for the AWD.

This doesn't state the AWD will get lower range in a mixed use yet. We need more information before we can draw that conclusion.

 

[MP3Mike]

This doesn't state the AWD will get lower range in a mixed use yet. We need more information before we can draw that conclusion.

Correct, we haven't seen the EPA ratings yet...

 

[voip-ninja]

This doesn't state the AWD will get lower range in a mixed use yet. We need more information before we can draw that conclusion.

I agree, but think about it this way.

Tesla wants to sell as many AWD cars as they can because they should be quite a bit more profitable than RWD cars.

Tesla is concerned that if AWD has lower range than RWD then it could hurt sales.

Tesla sandbags RWD range #s and asks the EPA to lower the #s from LR RWD testing knowing that they can then show "same" range for both versions even though they are not the same range.

Just seems like a very plausible explanation to me.

 

[Dr. J]

May we also stop repeating this marketspeak of 'torque sleep'? It is just a boring freewheeling of a deadweight, nothing fancy.

You're harshing the AWD buzz, dude!

 

[JGard]

You're harshing the AWD buzz, dude!

Dude, doesn't matter, AWD is still faster It's 100% of the reason why I'm getting it instead of RWD.

 

[ℬête Noire]

I was not aware of this fact and stand corrected. Thank you.

You were however spot on with "it's best to never have the mass that needs spinning up and things that'll have non-zero friction".

 

[ℬête Noire]

Dude, doesn't matter, AWD is still faster It's 100% of the reason why I'm getting it instead of RWD.

I'm getting it for the gaudy badge on the trunk lid.

X_x

 

[Thomas Edison]

I'm getting it for the gaudy badge on the trunk lid.

X_x

You're so vain, you probably think this post is about you.

 

[TesWhisperer]

We still need the EPA certification...

Wait.... they haven’t gotten EPA certification yet?...

 

[MP3Mike]

Wait.... they haven’t gotten EPA certification yet?...

If they have the EPA hasn't posted the details yet. I expect soon, now that they have the CARB one done.

 

[SoCalGuy]

Torque sleep still involves trying to control the current loop to 0. You can’t just spin a motor as deadweight without generating a back EMF. That’s especially true for permanent magnet motors, where they will passively generate if spun (it’s actually a serious electrical shock hazard to spin the shaft while the leads aren’t hooked up). In AC induction motors it also turns out to be true because the ferrous metals tend to be weakl magnetized over time. And that’s enough to generate just a little bit when spun.

Back when I was a motor controller engineer we actually used the latter effect to do sensorless startup on induction motors. It was a huge shock (no pun intended) that it worked — but we actually shipped it as a reference platform.

Can't this current be used to recharge the battery?

 

[Daniel in SD]

The EPA range will be much closer since at highway speeds most of the loss is aerodynamic drag not drivetrain friction. Might even be closer still real world if the AWD has stronger regen.
They need to add auto locking hubs to disconnect those front axles!
I would also like to say "I told you so"

 

[chillaban]

I was not aware of this fact and stand corrected. Thank you.

Do you have any insight into how 'big' this magnetization effect is and how it effects normal motor operation through its life, say after 150k miles, 10 years of operation?

It's pretty small. On the 300kW motors we were working on, passively dragging the motor at 50% of its max speed generated less than 1kW. I'm not sure if it has an appreciable impact on the lifespan of the motors. The kind of eddy current induced magnetic effects do cause some of your efficiency losses, but in reality your current and torque loops have to constantly adjust anyway due to noisy readings from your sensors. That's actually one of the higher-order losses for high-speed/high-amperage operation that a lot of people don't consider. When you look at the amplitude of noisy current readings when operating a motor at low speed vs high speed, the electrical noise at high speed makes it far more likely that 1 of your 15-30kHz control loop iterations operates on a completely nonsensical reading and leads to waste. You can try to be smart about processing and filtering, but all your simple methods of doing this lead to laggy readings which can be just as bad to efficiency.


(Hmm all of this is making me want to work on motors again )

 

[chillaban]

Can't this current be used to recharge the battery?

You don't want it to be, though. Passive generation is very poor efficiency (even for PM motors we quoted it as 30% the efficiency of active generation, which is your typical "regen", commanding negative torque through space vector PWM control)

Even if you get active regen efficiency, round trips through the battery cost efficiency. It's better to not make the energy you don't need rather than make it and attempt to store it again.

 

[thebigbobowski]

...it just becomes a LR Model 3 with ~150-200lbs more deadweight up front...

"I'm sorry. I know I said I'd give you a ride, but for optimum range, I have to choose between bringing you or my front motor."

 

[commasign]

I love the optimism on this board. Still holding out hope that Model 3 will have a HUD.

 

[apacheguy]

150-200 lbs is equivalent to having another passenger in the car.

Is that effect measurable? Of course. But I do not expect that to have a real world impact. For example, I don't plan trips any differently depending on the number of passengers in my Tesla.

The highway efficiency will be slightly lower than RWD but not by much. The reason this test showed an 8% hit is because a greater share of the horsepower was derived from the less efficient front motor.

 

[ℬête Noire]

"I'm sorry. I know I said I'd give you a ride, but for optimum range, I have to choose between bringing you or my front motor."

"....so unless you're willing and able to get out and help by giving a push start to keep my 0-60 under 5sec, you're going to need to call a taxi."

 

[Daniel in SD]

150-200 lbs is equivalent to having another passenger in the car.

Is that effect measurable? Of course. But I do not expect that to have a real world impact. For example, I don't plan trips any differently depending on the number of passengers in my Tesla.

The highway efficiency will be slightly lower than RWD but not by much. The reason this test showed an 8% hit is because a greater share of the horsepower was derived from the less efficient front motor.

I doubt it's using the front motor at all in this test. Why would you use the front motor when the rear is more efficient? The difference is probably mostly the friction from the axles (CV joints), gearbox, and front motor. The weight is probably a much smaller contributor since you get most of that energy back with regen. The highway efficiency should be much closer since the most of the loss at high speed is from wind resistance and weight hardly matters at all.