garygid said:
I thought ALL of the Tesla Regen was in the go-faster and only the mechanical brakes on the go-slower.
That's correct. You get maximum regen when you lift your foot off of the accelerator. As soon as you touch the brake pedal, friction brakes start. That's the thing I thought was crazy when I first heard about it, but after driving with it, it's what I prefer.
garygid said:
1. Does one get more than the "mild" Regen by pressing the brake pedal a little, or is the maximum Regen just the foot-off amount?
I don't want to be quoted as saying the regen level on the Roadster is "mild." I also don't want to get lost in describing the amount of regen you get from the Roadster, we don't have enough shared experience to provide a universal comparison. But I'm going to try again anyway by explaining how the RAV4-EV works.
In the RAV4-EV, when you lift off the accelerator, you get very light regen, but there are two switches that can change that. Without fiddling with switches, the regen is so light that we had to hook the car up to a tester and watch the regen current to see it is in fact giving us some regen.
A switch on the shifter gives you more regen on the accelerator, enough to very gradually slow to an upcoming light if you're paying attention enough to start early. Some people choose to drive in this mode all of the time, but it does introduce a very slight jerk when you move the pedal through the neutral position. It's not anything you'd notice at first, but after you know the car, I find it to be a bit of a distraction.
The level of regen can be increased further by moving the gear shifter into the "Electronic Braking" position. It feels like shifting into L2 in an automatic and gives you more regen, enough to slow more rapidly for an approaching light, or to hold a steady speed on a moderate downhill slope. It's not enough to hold your speed steady on a steep hill, which requires engaging the brake pedal. This mode introduces more of a jerk at the neutral point on the accelerator pedal, enough that I find it annoying. I would say this maximum level of accelerator pedal regen is comparable to mild braking, about the amount of braking you'd use to hold a steady speed going down a moderately steep hill.
I would say the Roadster's maximum regen is in the neighborhood of the strongest regen on the RAV4-EV, but the pedal feel is very smooth and the transition from acceleration to regen is gradual and easy to control. You may not even notice the transition, it just feels smooth and continuous. If you want the car to go a little faster, you push the pedal slightly forward, if you want to go a little slower you let up slightly. The difference between the Roadster and every other car I've driven is that you get more control in the slowing down range, although it's not as much as the engine braking you can get out of a manual transmission. It's very smooth through the whole range from maximum acceleration to maximum regen. If you're not driving like a jack rabbit trying to maximize time spent stopped at lights, then you can do most of your speed control with the one pedal. It's not something you think about, it just happens. When the car isn't slowing as fast you need, you put your foot on the brake pedal, just like any other car. Even if you don't know, or care, about regen, you'll still enjoy the wider range of control offered by the accelerator pedal.
When you touch the Roadster brake pedal, the friction brake engages and regen ends. It's very smooth, you don't feel regen cut off, in fact it took some careful observation to convince myself that's what happens.
Correction: It turns out I was wrong about this. Touching the brake pedal doesn't seem to change the regen level. If you're going fast enough to get max regen, it continues at that same level.
Again this sounded terrible compared to how the RAV4-EV works, but it has two big advantages. First, if you want to drive for maximum efficiency, you just need to use the accelerator to do your gradual slowing and use the brake pedal for more rapid slowing and to bring the car to a full stop. In the RAV4-EV, as you press the brake pedal, somewhere along the line you cross the transition from maximum regen to wasting energy with friction brakes, but you can't tell where that point is. So, it's impossible to reliably get maximum regen. With what Tesla has done, you can get maximum regen without looking at the instruments and without fiddling with any controls, just lift your foot. Second, it's a more natural and comfortable way to control a car's speed. I know it seems odd because it's not what we learned and have used all of our lives, but it really is just a change to the degree of slowing you get in an automatic transmission gas burner when you lift your foot off the pedal.
I'd like to again emphasize that this isn't big change to how the car drives for a driver new to the car. I had the opportunity to test drive the Roadster twice before we took delivery, once in September 2007 (when I had experience with a Honda Insight hybrid, but no EV driving) and again in September 2009 (after I'd been driving the RAV4-EV for two months). During those test drives, I didn't even notice the regen on the accelerator. It wasn't something I was looking for, and the car just worked. It was only after we took delivery and I started driving it daily that I noticed the regen, learned how to use it to maximum advantage, and eventually decided Tesla had done a marvelous job of designing the system.
I'm not asking that you blindly support this implementation of EV driving based on my rambling, but I am asking that you consider it possible that once we have cast off the limitations of the internal combustion engine, there could a small changes to how we control the car's speed that you'll find comfortably familiar but also different in a way you'll quickly come to prefer. I'm also hoping that Nissan will study the issue and consider how their customers can benefit from having an all-electric drivetrain controlled by a suitably optimized control system all within the requirement that it will work just fine for someone who has been driving gas for years or decades.
garygid said:
2. When your foot is off the "edie" pedal, is the brake light almost always on, unless the car is almost stopped?
I'm not sure of exactly when the brake light goes off as you slow down, since I can't normally see my brake lights. I've observed it some through reflection, and it does go off as the regen fades as the car slows.
garygid said:
3. In starting up from stopped on a flat surface, in forward "gear", without a foot on either pedal, does the car tend to move a little (creep), to simulate a typical automatic transmission?
Yes, that's the behavior, which is a controversial topic among Tesla owners. I think it's a good thing because it makes the feel of the car more familiar and it reinforces the training to keep your foot on the brake pedal when you want the car to not move.
When you turn the car off, a mechanical lock on the gear box engages, just like putting an automatic transmission in park.
I find myself in all groups when appropriate rather than one group. Anyone that is looking for efficiency in an EV would look to other EVs besides the leaf, it is a compromise on efficiency due to cost cutting/allocation to get it to the market at a specific price.
