Inside Electrify America’s plan to simplify electric car charging

Discussion in 'Tech: Batteries, Charging, Alternative Energy' started by EyeOnRivian, May 6, 2019.

  1. Hmp10

    Hmp10 Well-Known Member

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    One of the beauties of regenerative braking is "one-pedal driving", and you cannot have that unless regen engages whenever pressure on the accelerator pedal is lifted.

    One-pedal driving never factored into my decision to buy a Tesla, but it instantly became one of my favorite features. In fact, I quickly opted for the max regen setting. Using just the accelerator pedal I can slow down and speed up to adjust to traffic, go over speed bumps, troll for parking spots, and delay applying the brake pedal when coming to a full stop. I got used to it in about 5 minutes, and it works intuitively and seamlessly with the friction brakes. In fact, one of the most annoying things when I drive my ICE minivan is how frequently I have to go on the brake pedal -- something I never noticed before I got an EV; and I find it particularly annoying to have to keep my foot on the brake pedal at a stoplight -- something I do not have to do with the Tesla. (For people who miss the torque converters that cause stopped ICE vehicles to crawl forward when you release the brake pedal, Tesla has a "creep" feature one can engage to mimic that crawl, but I've never talked to a Tesla owner who uses it, and I have only seen one poster on the Tesla forums over the years who opted to engage it.)
     
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  2. EyeOnRivian

    EyeOnRivian Well-Known Member

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    One-pedal driving is not for everyone. And it's more than a matter of driving preference when it affects the potential safe handling of the vehicle in emergency scenarios that can lead to such things as over-steering or under-steering thus exacerbating the emergency. (Northern climate drivers not only contend with hydro-planning on wet/rainy roads but also with fish-tailing on snowy roads.) ICE drivers develop after decades of driving a skill, a sensitivity to handling a vehicle in emergency situations. One-pedal driving can seriously compromise that skill without the proper training. This article explains it much better than I can - "Why Regenerative Braking Belongs... On The Brake Pedal"

    Excerpt - "there is a serious error in the way regen is being controlled in some vehicles. A growing number of car makers put heavy regen on the throttle. This is a serious mistake. Putting heavy regenerative braking on lifting off the throttle violates some important principles of safety, ergonomics, human factors, driveability and vehicle dynamics."

    Plus, if safety isn't enough of a reason, I would think any EV manufacturer would want to help ease the transition of that ICE driver to that of driving an EV and not give them another excuse to not drive one. Giving the driver the option to regen on the braking not only provides familiarity but most importantly allows them to feel confident they will be able to use those skills they developed in handling their vehicle in emergency situations.
     
  3. Hmp10

    Hmp10 Well-Known Member

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    #23 Hmp10, May 21, 2019
    Last edited: May 21, 2019
    I agree that it might be a good idea for Rivian to give buyers a way to control how they want regenerative braking to engage. But that choice should also include the ability to use one-pedal driving. Having driven a Tesla for four years, I would not buy an EV without it.

    As for that article, its source is not identified, but the writer seems to be a competitive driver. For instance, he's an advocate of left-foot braking for general driving, although it is something that almost no one deliberately uses outside of extreme performance driving. He also incorrectly claims that almost no EVs other than Tesla put any regenerative braking function in the accelerator pedal. The Chevy Bolt, for instance, puts even more regenerative braking into the accelerator pedal than Tesla. A Bolt enables one-pedal driving and, with the use of a column-mounted stalk, can actually bring the car to a full stop without ever using the brake pedal -- something Tesla does not do.

    Also, this driver claims that Tesla drivers are often thrown off their game in using one-pedal driving when at or near full battery charge, because a full battery cannot accept regenerative energy. I almost always leave my home with a full charge and often drive the car deep into its range before returning home. I notice absolutely no difference in the braking behavior of the car. Perhaps that is because Tesla's software begins to engage friction braking using accelerator inputs when the battery is nearly full; or perhaps it is because, in order to increase battery life, Teslas are seldom charged above 85% except when charging for a long trip between charging points, so there is almost always plenty of battery capacity to absorb regenerative energy. Even if starting with 100% charge, a few miles of driving will open up enough capacity to absorb regenerative braking energy. (I often wonder how many people who hold forth about driving Teslas have actually driven one. I certainly know most of the people who trash Teslas on the internet have never driven one, much less owned one, and get most of their "information" from each other.)

    Although I am not a race driver, I have done some hard acceleration runs in my car and brought it down hard from high speeds and searched out a few hard corners to test its handling prowess where mid-corner braking was necessary. (I have owned Corvettes, Mercedes SL55's, and traded an Audi R8 V10 Spyder for the Tesla and wanted to compare the two. I was shocked at how stable the Tesla was even when pressed hard.) There is nothing about the regenerative braking that unsettles me or the car. In fact, when braking from high speed, one travels quite a few feet in the brief moment it takes to get your foot off the accelerator and to press the brake pedal to the point of engagement. With regenerative braking in the accelerator pedal, the car is already braking during that time. I have sometimes wondered if that's why a car as heavy as a Tesla on relatively skinny tires posts such extraordinarily short 60-0 braking distances.

    The author claims that ergonomics dictate that no slowing function should be incorporated into an accelerator pedal, as its function is only to speed up the car, and putting any slowing function in it will throw drivers off. First, I would like to know an authoritative source for such a claim. Second, I find his attempts rather lame to explain why ICE cars, which also slow down when your foot comes off the accelerator pedal, do not also unsettle the drivers. Also, he gives no consideration to how differently an ICE car behaves when backing off the accelerator depending on whether one is driving a manual or an automatic transmission car. I suspect the real reason his ergonomics argument falls apart is that drivers very quickly get used to how their cars respond to accelerator inputs, both going on and coming off the pedal.

    Drivers intuitively adapt to the braking characteristics of their cars, even if they don't realize it. Even in ICE cars, a car's response to its friction brake pedal varies widely from brand to brand and even from car to car. Some cars engage the brakes deeper into the pedal travel than others. Power brake assist varies widely. Braking in some cars is much more linear than in others. Forward weight shift during braking varies widely between cars. All of these things can critically affect performance in emergency braking an ICE car and get a driver unfamiliar with the particular car in serious trouble.

    Also, these days a growing number of ICE cars have an emergency braking function that sometimes engages before the driver is even aware of the situation and then increases the haul-down rate of the car beyond what the driver can achieve with the brake pedal, thereby taking much of the control away from the driver in emergency situations. I would argue this creates far more problems for driver control during emergency maneuvers than anything regenerative braking does.
     
  4. cllc

    cllc Member

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  5. cllc

    cllc Member

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    Hmp10,Well said, The only condition that I can think of that regen braking is not desirable is in icy conditions as I found out the first day I drove my brand new model 3 to work in February and there was glazed black ice on the highway. Otherwise I can vouch that regen braking makes the vehicle safer to drive in all other conditions that I can think of.
     
  6. Feathermerchant

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    I expect that EV mfrs will in time add anti slip/skid to the regenerative braking routine. It should be fairly easy. Then there should be no question.
    I agree with the other EV drivers here. Once you have experienced one pedal driving you'll not want to go back. It makes you lazy.
     
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