Model S regen

[Doug_G]

I did talk to Tesla engineers that during the times when regen is reduced or disabled for those reasons above, the behavior of the car is different and that isn't particularly safe (and it's alarming unless you're expecting it). I'm not sure what they've done to improve this in the Model S, if anything.

The Roadster displays the NO REGEN symbol on the dash, but you can easily miss it - and I did the first time! That was startling!!!

This is the one case where I might actually appreciate hearing the annoying brap-brap-brap sound. I say annoying because every time I use my A048's it goes off saying the TPMS has a problem (no sensors!).

 

[vfx]

BMW has said that regen is part of the driving experience.

Now Audi is doing the same.

http://blogs.insideline.com/straightline/2012/06/a3-e-tron-paves-way-for-audi-evs.html

The steering-mounted paddle shifters we mentioned above also control regenerative braking (as there is no gear shifting to control). The left paddle increases the degree of regeneration in four increments, the right paddle reduces it.

How awesome is that!?

 

[Vger]

Tesla is missing the boat here. On a car as powerful as Model S, one really needs more regen, and more control over it. I think the paddle "shift" is a great idea! At the very least, they should have THREE levels on the touch-screen, rather than two. The more aggressive level could be "Sport", just as they do for the steering effort. This was my ONLY complaint with the driving dynamics after my test drive.

 

[JRP3]

Stronger regen levels might stress the cells too much and/or drive the pack voltage too high, which would cause regen to cut back anyway.

 

[Vger]

I have several bits of evidence to indicate that they have nowhere near maxed out the regen on Model S:

1) The motor can DRAW more than 300 kW from the battery to drive the motor. The system is reversible, so the battery's regen capacity should be about this much.
2) We know that the Roadster was originally tested with much more regen, but they found in early testing that it was too easy to lock the rear wheels and spin the car that way, so the backed it off (quite a bit).
3) I commented on the weak regen on my test drive, and my co-pilot admitted that they had set up the car for first-time EV drivers and did not want to surprise them with aggressive regen. The implication was there was a lot of upside in the regen.
4) In a personal conversation with Model S Program Director Jerome Guillen, he told me that driving the Model S alpha to work every day, he turned the regen up really high, and said it was much more aggressive than the roadster.

So I am quite sure that a higher setting is quite within the car's engineering parameters. I only wish they would trust their customers to be able to handle a third higher "sport" setting on the touchscreen. Heck, they allow you to turn off the traction control, and that is much more risky!

Actually, from my two years experience with the Roadster, I think it is less safe to have such weak regen. I rely heavily on regen driving the twisty mountain road to my house. I almost never need to touch the friction brakes while decelerating for corners. It is so easy and intuitive to just modulate the accelerator pedal constantly. I am concerned that especially the performance version will be too easy to speed up and not easy enough to slow down!

 

[goyogi]

It's probably an easy software upgrade. Let's get the cars out and more real world feedback to Tesla and I'm sure we'll have more knobs to tweak and data to gawk at within a year.

 

[JRP3]

1) The motor can DRAW more than 300 kW from the battery to drive the motor. The system is reversible, so the battery's regen capacity should be about this much.

It actually depends on the cell properties, they are often not symmetrical in their charge/discharge capabilities. Generally cells can discharge at much higher rates than they can accept charge.

 

[bluetinc]

Vger,

While greater regen might be possible, I doubt it would be good for the batteries. The current max regen is 60KWH, which is about C/1.4. That really is a lot of power moving into the batteries, and getting close to the C/1 rate the super charger has(90KWH), which we know Tesla does not want to be regularly used. In fact, I expect that the max regen will be reduced in the smaller batteries to keep somewhere near the C/1.4 charge rate...

Peter

 

[TEG]

...Our copilot said to drive over the potholes to feel the suspension...

The air suspension does such a good job of soaking up the bumps that I wonder if people might damage their tires and/or wheels due to lack of concern for potholes and such? Those low profile tires might suffer from too many slams through the bumpy stuff.

... I understand that Roadster drivers like the accel-decel of their go pedals but I think the Model S is a different car and needs to drive with subtlety and to me this means it needs to coast without effort on the part of the driver. I would also like the regen to be regulated by the brake pedal and to be able to put back lots more energy into the batteries than with the current programming.

Having had a lot of experience with different cars and in particular with electric conversions, I believe the word which best describes the way to efficient operation is "coasting". It is simply the way to the least energy consumption. In hypermiling, you avoid stops at the bottom of hills, use the brakes as little as possible, and regen as much as you can if you have to slow down. Kinetic energy (speed) and potential energy (altitude) are king...

Different people have different opinions and different likes/dislikes with regards to the regen behavior. Many wish it could just be adjusted to driver preference (including making changes during your drive when you encounter different conditions). Yes, many Roadster owners really like heavy regen with "one pedal driving" being possible. Yes, some people used to luxury cruising and automatic transmissions might find coasting more familiar.

You might be able to debate which mode is better for efficiency. With one-pedal regen why not just rest your foot on the go pedal so that you get the car to coast? You don't have to always let all the way off to invoke max non-braking regen...

Anyways, the regen debate will live on, and on...

 

[CroDriver]

Oh, regen would be awesome with a lever where the open spot is - the stick shift spot
similar to the RIMAC BMW

The lever-activated regen is great. I love to drive the e-M3, especially because of this feature. It is not only great for city and open-road driving, but it gives completely new possibilities for drift-maniacs like myself. However, the problem is that this solution can't be homologated (at least in Europe). The authorities are very strict about safety-relevant features of the vehicle so a car manufacturer must design the car around the existing rules. The authorities are not very open minded for new ideas so don't expect too much from EVs - the technology can do a lot, but the OEMs can't use the potential because of the legislation.

We are testing 4 different regen set-ups:

1. Lever (0-100% = 0-100 kW of braking power). This is my favorite.

2. Regen activated by braking (on/off) - installed in a mule with a gearbox. The ECU shifts the braking torque based on speed and gear, and also has a ramp-up and ramp-down of torque for a smoother feel. I really don't like this set-up. The BMW Active-E regen works like this. I have never driven one - I wonder how the regen feels in that car. Probably it brakes with less torque than our mule but even when we reduce the torque it feels strange.

3. Regen activated by braking - regen increases with more force applied to the brake pedal - works similar to a normal brake (the driver doesn't feel the difference). When the regen reaches 100%, the mechanical brakes step-in. This is installed in a 800 kW, AWD prototype. The driver can adjust the regen from 0 to 800 kW so the friction brakes are not needed except at the racetrack.

4. Accelerator activated regen - similar to Tesla's. Not my favorite but it works smooth.

The e-M3 has RWD so we can't regenerate as much as with an AWD car. Still, I usually regenerate 25-40%. Thanks to the hand-operated lever I am sure that no friction brakes are used, except when I want it. It is hard to regenerate that much with option 2. and 4. I know - it sounds strange to brake with a hand-operated lever but everyone who tested the car loved that feature. It really feels natural.

If someone happens to be in Croatia for vacation, I will be more than happy to allow a test-drive in our prototypes.

Btw. I want to make a video on this topic (different kinds of regen) for a while now but I simply don't have the time for it. I'll do my best to find some time in the coming weeks.

Sorry for the Off Topic. :redface:

 

[CroDriver]

I heard that same high pitch tone in the MSP I drove every time I punched it straightline, too. I did several "regen down to 30 mph, punch it up to 60 mph" runs along the highway and heard that sound each time at max motor exertion, so I didn't think it was related to the traction control. Seemed more related to inverter/current delivery.

Then again, I suppose it's possible the car started detecting slip during hard straightline acceleration as well. That's a lot of torque to put down in two wheels. Some lightweight big block cars like the Corvette Z06 have no problem breaking traction in a straight line at speed after a downshift. I'd be impressed to learn the Model S at 4600 lbs can break traction under acceleration at 30mph!

From your explanation - this is the motor controller changing the switching frequency. The controller is more efficient at lower frequencies but also louder. It probably works on a higher switching frequency during during "normal driving" (within the continuous rated motor-controller power/current) for silent operation. When you floor it and the looses (heat) increase, the controller changes the frequency in order to increase efficiency. You will hear that as a whine from the rear end of the car.

 

[Brian H]

...
P.S. Wait! If I'm the one causing a traffic jam, then I'm in front of it and I can just zoom away in any case! :biggrin:

You one of the guys who does that just for fun? I've always suspected there were a few like you around ...:cursing:

:tongue:

 

[Brian H]

I'll figure something out. Might take some practice.

Always wondered how those jenyusses get back on the road. Un-drifting is not an option. Hope the other guy clears out first, I guess!

 

[Brian H]

I'm not sure that the Roadster and the S are doing the same thing when you take your foot off the "Go-Pedal".
...

That's "Goose Pedal".
Goose it, James! :biggrin:

 

[vfx]

The argument for breaks is also ever lasting.

The car's and the spelling.

 

[brianman]

at vee eff ex - Bee careful about braking your quote rapper tugs.

 

[MikeK]

From your explanation - this is the motor controller changing the switching frequency. The controller is more efficient at lower frequencies but also louder. It probably works on a higher switching frequency during during "normal driving" (within the continuous rated motor-controller power/current) for silent operation. When you floor it and the looses (heat) increase, the controller changes the frequency in order to increase efficiency. You will hear that as a whine from the rear end of the car.

At the Palo Alto event today, we were told that there is a connector through which very high current passes under heavy acceleration. It's AC, and the particular frequency causes the connector to physically vibrate, which is audible in the car. Apparently, they are considering modifying the frequency so that the connector will not whine audibly.

 

[goyogi]

At the Palo Alto event today, we were told that there is a connector through which very high current passes under heavy acceleration. It's AC, and the particular frequency causes the connector to physically vibrate, which is audible in the car. Apparently, they are considering modifying the frequency so that the connector will not whine audibly.

To add a data point, one Tesla co-pilot I talked to said that at full throttle there is a difference in sound between performance and standard. But identical in sound during casual driving.

 

[brianman]

To add a data point, one Tesla co-pilot I talked to said that at full throttle there is a difference in sound between performance and standard. But identical in sound during casual driving.

TEG, hook us up?

Edit: I'll give it a shot...

Non-Perf @ 12:21 [Mods: I wish I knew how to set the embed start time]

Perf @ 8:41

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<embed src="http://www.youtube.com/v/FKYmxYwEfFQ&start=741s" type="application/x-shockwave-flash" allowfullscreen="true" allowScriptAccess="always" width="640" height="360">
</object>

 

[smorgasbord]

Some Model S test drive regen thoughts from a Roadster owner:

At first, Model S regen felt less than Roadster. At first I thought this was due to the weight of the car giving it more momentum, but I was subsequently told that Model S regen is ramped up when you lift off the accelerator. Roadster regen is about 40kW while Model S is 60kW, which corresponds reasonably close to the weight ratios of the two cars. After the test drive, drove the Roadster on some of the same roads and regen on it seemed reasonably close to Model S.

Feathering the pedal to give zero acceleration/regen was easier on Model S than on Roadster.

Finally, regen is all rear wheel braking. Usually, the safest and most controllable braking is done via front brakes. So, you don't want too much rear wheel only braking for safety and control. Finally, unless it's different than Roadster, regen braking is not anti-lock controlled. On Roadster, if you're in heavy regen and the rear wheels lose traction you'll lose all braking and the car will feel like it's lurching forward (even though it's only going into coasting). The more regen you have on the rear wheels, the more you might be depending on that braking and so the more trouble you can get into with too much rear wheel regen. The 4-wheel drive Model X should have regen on all 4 wheels, which should be a treat.

So, while my feeling is to ask Tesla for more regen on Model S, I'd like to first know why they didn't give Model S more. It may be for our own good.