Disrupt: The Tesla Model S P85D Reviewed

[rage2]

Finally got a chance to drive a P85D spec Model S. Let's see if it'll add even more fuel to the Tesla thread fires.

I focused specifically on the EV's car abilities in this review, ignoring all the discussions we've made about Tesla's stock, Tesla as a company, and everything else that was a distraction on the car itself. Enjoy!

http://www.beyond.ca/disrupt-the-tes...wed/53132.html

[The_Rural_Juror]

Totally agree with your comments on the interior.

[Cos]

.

[JRSC00LUDE]

Pretty balanced, nice writeup.

[rage2]

Originally posted by The_Rural_Juror
Totally agree with your comments on the interior.

Tesla has been updating the delivered cars pretty much monthly, maybe even weekly. The specs of this P85D is already different than what you order today. It keeps changing. The new seats are a huge huge improvement. I can't state that enough. So it's up to Tesla to really improve that interior quickly, which they seems to be able to do much faster than traditional manufacturers (ie facelifts).

A point that I neglected to include in the review is that there are no voice commands to control most of the functionality, so you have to use the touch screen for nearly everything. Voice control only supports simple commands such as picking a song, navigate, or send a bug report to Tesla. Both my times with the Model S, I had the passenger work on the settings. Didn't feel comfortable fiddling around with it while driving.

Originally posted by Cos
Good article. I assume this was one of the two 'beyond' Tesla's?

Yup. Thank you B18B for letting me get behind the wheel of his P85D!

Originally posted by Cos
This part: really reminded me of what the new EZ-GO golf carts feel like. They also have regen braking and feel the same way. Is weird at first but I quite like it actually, feel like I have more control.

I drive a lot of different cars, so I was able to adapt pretty quickly and had zero problems with it. I don't think we're your typical drivers though, and it shows over on the Tesla forums. Lots of owners complaining about this behavior, wanting more settings to make it feel right, wives complaining, etc.

[hurrdurr]

Two car seats in the back awesome!

[Gripenfelter]

Good write-up.

So this one didn't have the Ludicrous speed button?

[BerserkerCatSplat]

The exception that I would like to point out is off throttle behavior. In a normal car, when you completely let off the throttle to cruise, you are met with a very small amount of engine braking. In the Tesla, to optimize range and efficiency, it feels like you’re lightly on the brakes. This is because off throttle, the Model S is regenerating power to charge the batteries. It takes a little while to get used to this behavior, but once you do, you pretty much never use the brake pedal in normal driving situations, and reprograms the driver to use a single pedal to control their speed. The Model S isn’t the only EV forcing drivers to relearn how to drive, the BMW i3 uses a similar system, and there is a good reason why EVs are moving towards this behavior.

Looking at the Toyota Prius, it handles regenerative braking slightly differently than the Model S and i3. Off the throttle, it simulates typical engine braking, and regenerates a small amount of energy. Press the brakes a little, and it activates more regenerative braking. Push hard on the brakes, and it will regenerate energy and use the mechanical brakes to slow you down quicker. There are pros and cons to this method of energy recovery. The obvious advantage is that it feels like driving a typical car. The disadvantage is that it requires a more complex braking system to manage the transition between regenerative braking and mechanical braking, something that Toyota has done an excellent job of, at a significant increase in engineering and control systems expenses. Another side effect is that drivers tend to use the brakes more, which means more brake wear, and less energy going back to the batteries.

Which system is better? For efficiency sake, the single pedal speed control model is definitely the way to go.

This part was by far the most interesting to me - it's nice to hear how the engineering choices affect the drivability profile. That said, I was surprised that you picked the "single-pedal" system as the winner in the efficiency category. If the Prius variable regen-brake system has a higher maximum braking force from the regen system alone than the single-pedal fixed regen (so the Tesla doesn't feel like it's hit a wall every time you get off the throttle), wouldn't that mean that the variable system will innately provide a greater level of regeneration and lesser brake wear, as the brakes only need provide force over and above the maximum force applied by the regen system?

Solid article overall, I'd honestly like to see a similar review for the current Volt, even if it is a bit more pedestrian than the Tesla. I must be getting old.

[s dime]

Originally posted by BerserkerCatSplat


This part was by far the most interesting to me - it's nice to hear how the engineering choices affect the drivability profile. That said, I was surprised that you picked the "single-pedal" system as the winner in the efficiency category. If the Prius variable regen-brake system has a higher maximum braking force from the regen system alone than the single-pedal fixed regen (so the Tesla doesn't feel like it's hit a wall every time you get off the throttle), wouldn't that mean that the variable system will innately provide a greater level of regeneration and lesser brake wear, as the brakes only need provide force over and above the maximum force applied by the regen system?

Solid article overall, I'd honestly like to see a similar review for the current Volt, even if it is a bit more pedestrian than the Tesla. I must be getting old.

That's what I would assume as well, less break wear not the other way around.

[killramos]

Originally posted by Gripenfelter

So this one didn't have the Ludicrous speed button?

From what I understand none of them do?

I wonder if Tesla has thought of maybe putting something like a coast button on the wheel. Hold the button and it disabled the regen system allowing you to smoothly coast down a slight hill without losing or gaining much speed. Much more efficient to do that than to:

regen-accel-regen-accel

I could see that actually increasing range dramatically in a situation like say driving to kelowna from calgary.

Similar to the coasting function efficient dynamics BMW's have.

I don't fully understand the drive train but can the motors be decoupled from the wheels to do this?

[rage2]

Originally posted by hurrdurr
Two car seats in the back awesome!

Yea, my gf loved that setup. In fact, she loved the Tesla after seeing it in person and loved it. At least, until she spec'd it out on the website.

If the P85D was a $100k car, we'd probably get one for her as a year round DD. At this stage, we're probably going to look for a used one to see how prices look in 2.5 years.

Originally posted by Gripenfelter
So this one didn't have the Ludicrous speed button?

Only the newly delivered cars have it. This car is compatible with the upgrade.

Originally posted by BerserkerCatSplat
That said, I was surprised that you picked the "single-pedal" system as the winner in the efficiency category. If the Prius variable regen-brake system has a higher maximum braking force from the regen system alone than the single-pedal fixed regen (so the Tesla doesn't feel like it's hit a wall every time you get off the throttle), wouldn't that mean that the variable system will innately provide a greater level of regeneration and lesser brake wear, as the brakes only need provide force over and above the maximum force applied by the regen system?

It all depends on driver "retraining" when using the single pedal system. I was pretty aggressive in traffic, and really didn't use the brakes at all, and was able to fully control my speed with a single pedal, meaning I'm regenerating as much as I can. After a few minutes, you're never off the throttle completely, unless you're coming to a complete stop.

In a Prius, I have no idea when I'm using brakes if I'm using brakes or regen unless I'm staring at the pretty screen. So as a driver, if I'm to maximize efficiency, the single pedal solution is better.

Like I said earlier, while it's easy for me to adapt, it's clearly an issue with many drivers as they're having difficulty adjusting to this setup.

Originally posted by s dime
That's what I would assume as well, less break wear not the other way around.

You never touch the brake pedal in the Tesla unless you want to panic stop, or drive really aggressively ie at the track.

Originally posted by killramos
I wonder if Tesla has thought of maybe putting something like a coast button on the wheel. Hold the button and it disabled the regen system allowing you to smoothly coast down a slight hill without losing or gaining much speed. Much more efficient to do that than to:

regen-accel-regen-accel

I could see that actually increasing range dramatically in a situation like say driving to kelowna from calgary.

You don't need to. You just hold the throttle at say 10% and it's smoothly maintaining speed while regen charging going downhill. Or use cruise control, which does the same thing. Once the driver learns to use the single pedal method, it's a more efficient system. I guess I should've noted that point in the review.

[killramos]

Originally posted by rage2

You don't need to. You just hold the throttle at say 10% and it's smoothly maintaining speed while regen charging going downhill. Or use cruise control, which does the same thing. Once the driver learns to use the single pedal method, it's a more efficient system. I guess I should've noted that point in the review.

So the car can regen while on throttle? Somehow that doesn't make sense to me.

So i guess the brake pedal is just for the mechanical brakes then?

[rage2]

Originally posted by killramos
So the car can regen while on throttle? Somehow that doesn't make sense to me.

So i guess the brake pedal is just for the mechanical brakes then?

Yup. Once you get going, the first 20% of throttle travel is regen at various levels. So to maintain constant speed, you're at say 21% throttle. Want to slow down a bit? 10% throttle. Want to slow down more? 0% throttle. Oh shit a kid, hit brake pedal (and trigger mechanical brakes).

[B18C]

The regen system is very smooth. If I'm coasting down a hill I control speed by how much i'm pressing down the accelerator (or brake). I can still be in regen mode while pressing the accelerator so there isn't a situation where I go regen-accel-regen-accel.

When I let off the accelarator the regen is not jarring or anything. In fact, I wish there was a mode to have even more aggressive regeneration.

One pedal driving takes a bit of getting used to but now it's second nature.

[BerserkerCatSplat]

Originally posted by rage2

It all depends on driver "retraining" when using the single pedal system. I was pretty aggressive in traffic, and really didn't use the brakes at all, and was able to fully control my speed with a single pedal, meaning I'm regenerating as much as I can. After a few minutes, you're never off the throttle completely, unless you're coming to a complete stop.

In a Prius, I have no idea when I'm using brakes if I'm using brakes or regen unless I'm staring at the pretty screen. So as a driver, if I'm to maximize efficiency, the single pedal solution is better.

Like I said earlier, while it's easy for me to adapt, it's clearly an issue with many drivers as they're having difficulty adjusting to this setup.

Well I agree that it makes for a smoother transition on the driver's part, I'm comparing the pure electromechanical efficiency of the two systems.

A bit of research shows that the Prius also kicks in regen in off-throttle situations, but it may just be that it's set for a lower level of regen in that situation than what you experienced the Telsa. The Model S, AFAIK, has three off-throttle regen settings (Standard, Neutral, Low) that set regen rate at zero throttle input, I'm not sure which you were in. Standard appears to light up the brake lights when you're off the gas but I can't nail that down for certain.

So it seems intuitive that using a regen system that's modulated by the brake pedal is still going to give better efficiency and reduced brake wear over the split system. Both will regen up to the max deceleration input from the regen system regardless of whether that's based on input from brake or throttle pedal as the Prius brakes don't kick in until you hit max regen rate, which is significantly higher than the Teslas as it can be regulated to a higher regen rate. It's basically brake-by wire.

However, here's what I've now learned from researching the systems.

The method of regen modulation currently doesn't make any difference to regen efficiency. It doesn't even make a difference to maximum regen rate, either, which came as a real surprise to me. It all comes down to batteries.

In theory, if the Tesla had it off-throttle regeneration capped at (say) 60kW for drivability, and the Prius could regenerate 120Kw while under full braking power, the Prius would have a higher maximum efficiency as it would generate 60kW at the same deceleration rate as the Tesla but have the ability to generate more kW (and charge the battery faster) under heavier braking.

That makes sense in theory, but what that theory requires is a battery than can accept a charge rate equal to the maximum regen output (60kW, 120kW, etc.) That battery, unfortunately, doesn't exist. So, any and all regen rates must be capped at the maximum charge power the battery can accept. In theory, we could have regen do 100% of the braking job at all times and waste no energy whatsoever, but since batteries have a max input rate that's not feasible.

So the reality is that both the Tesla and Prius (and Volt, etc.) will only regenerate to the maximum input power the battery can sustain. Both will be exactly equally efficient given the same battery. Whether they actually both have the same max charge rate I don't know - Tesla Model S batteries have a max regen input of 60kW, while previous gens of Prius are only 30kW but they may have upgraded batteries now.

[dirtsniffer]

#mercedes lol

I like that method for regen. seems like it is the best use of the system while being easy to use for the general public.

For me, never having driven a electric car, I think I would prefer to have a steering wheel paddle to switch the motor polarity for regen and have the brake peddle for the conventional system.

[killramos]

Originally posted by rage2

Yup. Once you get going, the first 20% of throttle travel is regen at various levels. So to maintain constant speed, you're at say 21% throttle. Want to slow down a bit? 10% throttle. Want to slow down more? 0% throttle. Oh shit a kid, hit brake pedal (and trigger mechanical brakes).

Interesting. I just feel like there has got to be some benefit to being able to coast with the drive train disconnected. Just physics really.

Kind of like the concept of hypermiling, i know coasting features are a main way that a lot of other cars get better mileage. One of the reasons why modern autos do better than manuals.

[rage2]

Originally posted by BerserkerCatSplat
The method of regen modulation currently doesn't make any difference to regen efficiency. It doesn't even make a difference to maximum regen rate, either, which came as a real surprise to me. It all comes down to batteries.

In theory, if the Tesla had it off-throttle regeneration capped at (say) 60kW for drivability, and the Prius could regenerate 120Kw while under full braking power, the Prius would have a higher maximum efficiency as it would generate 60kW at the same deceleration rate as the Tesla but have the ability to generate more kW (and charge the battery faster) under heavier braking.

That makes sense in theory, but what that theory requires is a battery than can accept a charge rate equal to the maximum regen output (60kW, 120kW, etc.) That battery, unfortunately, doesn't exist. So, any and all regen rates must be capped at the maximum charge power the battery can accept. In theory, we could have regen do 100% of the braking job at all times and waste no energy whatsoever, but since batteries have a max input rate that's not feasible.

So the reality is that both the Tesla and Prius (and Volt, etc.) will only regenerate to the maximum input power the battery can sustain. Both will be exactly equally efficient given the same battery. Whether they actually both have the same max charge rate I don't know - Tesla Model S batteries have a max regen input of 60kW, while previous gens of Prius are only 30kW but they may have upgraded batteries now.

Great info. I missed this during the research.

Originally posted by dirtsniffer
#mercedes lol

I like that method for regen. seems like it is the best use of the system while being easy to use for the general public.

For me, never having driven a electric car, I think I would prefer to have a steering wheel paddle to switch the motor polarity for regen and have the brake peddle for the conventional system.

That's the thing, it's a great system for those that can adapt, but for most drivers, they just can't get used to the system. There are a lot of complaints about it in the Tesla forums.

A steering wheel paddle would make even less sense if someone can't adapt to a regen with less throttle system.

Originally posted by killramos
Interesting. I just feel like there has got to be some benefit to being able to coast with the drive train disconnected. Just physics really.

Kind of like the concept of hypermiling, i know coasting features are a main way that a lot of other cars get better mileage. One of the reasons why modern autos do better than manuals.

At a certain pedal position, it basically coasts. Doesn't add power, doesn't regen. It's tough to hit that mark though, and you have to look at your speedo to find the sweet spot, as it shows power usage and regen.

You're right tho, it's probably more efficient to go slightly faster downhill via coasting, once it drops back to your cruise speed, power again to maintain speed. Unfortunately, it's not a realistic option because of speed limits.

[killramos]

Originally posted by rage2

You're right tho, it's probably more efficient to go slightly faster downhill via coasting, once it drops back to your cruise speed, power again to maintain speed. Unfortunately, it's not a realistic option because of speed limits.

Somehow i have a feeling there is no way to decouple the wheels from the motor actually, which is why it isn't done.

Is there a neutral function on the car at all?

There must be or how could you ever get the thing on a flatbed to tow.

edit:

To put in Neutral, just one upclick on the gear stock from Drive without pushing it in for Park puts it in Neutral.

looks like it can and does in some situations:
http://my.teslamotors.com/de_AT/foru...in-and-puddles

Maybe coasting is just a software update away!

[B18C]

Originally posted by rage2

Great info. I missed this during the research.


That's the thing, it's a great system for those that can adapt, but for most drivers, they just can't get used to the system. There are a lot of complaints about it in the Tesla forums.

Really? I don't get that impression on the forums at all.

I haven't looked into it for a while now but I thought one pedal driving has been very well received by Tesla drivers. If you really don't like it you can turn it off. You can also turn on "creep" that makes the car behave just like it had an automatic transmission if you want.

If my wife ever wanted to drive my car I would do just that. Turn on creep and turn off regen and it will behave just like any other car she has driven.