Tesla question

"PartyPooper2012" (PartyPooper2012) 06/23/2020 at 16:16 • Filed to: None

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Say you’re driving along on a level road and suddenly come across a steep downhill. Is there a way to downshift? Does Tesla just runaway? Does it maintain original speed?

How does it even work???

For Sweden > PartyPooper2012 06/23/2020 at 16:21

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I think it flips on the ol’ regenerative bra k ing switch

Maxima Speed > PartyPooper2012 06/23/2020 at 16:24

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Regen braking

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > PartyPooper2012 06/23/2020 at 16:24

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Only one gear, so no downshifting.

Most electric cars will automatically regenerative-brake to some extent when the accelerator pedal is not being pressed. So I would assume that the Tesla would simply increase the motor resistance to maintain the correct speed; the side effect of which would be charging the battery pack.

farscythe - makin da cawfee! > PartyPooper2012 06/23/2020 at 16:28

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wait downshift?

on a downhill?

oh wait...im a cyclist

Chan - Mid-engine with cabin fever > PartyPooper2012 06/23/2020 at 16:30

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EVs constantly monitor the acceleration/deceleration with respect to engine output, so if the balance suddenly changes the regen will kick in.

CarsofFortLangley - Oppo Forever > PartyPooper2012 06/23/2020 at 16:31

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It speeds up, crashes into the median and wakes up the driver.

CompactLuxuryFan > PartyPooper2012 06/23/2020 at 16:33

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The regen on any Tesla can be set to be stronger than the engine braking possible on most cars. They will slow down dramatically unless you’re actively on the gas, which is why one pedal driving is possible. Let’s say you don’t have regen on for some reason, you just use the regular brakes... in this scenario you  can think of EVs as behaving as if you left your ICE car in first the whole time.

CobraJoe > PartyPooper2012 06/23/2020 at 16:35

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Side note: My father in law recently bought a 3rd gen prius. I drove it a few times, and overall it’s pretty unimpressive (as expected). Not bad, just nothing to get excited about. (though the driving position is horrible for my large frame).

But the braking is surprisingly satisfying . There is significant deceleration with minimal pedal movement, and rather easy to modulate.  I never would have expected that regenerative braking would be so natural and downright enjoyable.  

fintail > CarsofFortLangley - Oppo Forever 06/23/2020 at 16:38

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Autopilot!

WilliamsSW > ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) 06/23/2020 at 16:39

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I drove a Tesla a while back. What you describe is sort of what happens, but Teslas take some getting used to. Any time you take your foot off the gas, you slow down a lot more than an ICE car would. It’s more like driving a manual transmission and leaving it in 2nd or 3rd at higher speeds.

I suspect that the Tesla would actually slow down on most hills.

Unless you’re using autopilot, in which case...

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > WilliamsSW 06/23/2020 at 16:58

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That’s the more aggressive regen activating. When you hear about so-called ‘one pedal’ driving, it is because the aggressive regen braking slows the car so much you rarely need to stop fully. 

GLiddy > CobraJoe 06/23/2020 at 16:59

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I had a hybrid Lexus for a few years. The hybrid system acceleration and braking was interesting. It had a CVT transmission so there was only Park, Reverse, Neutral, Drive and Low.

In Drive, when you went down a hill, the car would speed up signi ficantly as if it was coasting in neutral. With practice you learned to gently engage the brake pedal and you would see the KW/h meter go into into the generative range and start replenishing the battery and reduce the car’s tendency to speed up. If you hit the brakes harder, the friction braking would kick in.

On one trip into the mountains in North Carolina, we crossed the Appalachian Trail at the peak of a mountain and started coming down the other side headed toward Cherokee, NC. I put the car in Low (S) and the car seemed to automatically engage the regenerative braking and keep the battery full and keep the speed under control. I didn’t use the brakes really at all. It didn’t seem to use the engine for braking either. I never quite understood where all the energy that had to be dissipated doing this went to. Maybe it did expend it in the transmission and engine, or perhaps it has a method of using the induction motors to retard the vehicle’s speed even when the traction battery is full.

I’m guessing Tesla must use similar means to scrub speed before resorting to friction braking.

ZHP Sparky, the 5th > PartyPooper2012 06/23/2020 at 17:13

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Are you trying to glean something specific to Teslas with this question, or EVs in general? Are you referring to autopilot or just driving yourself?

With one pedal driving you keep constant pressure on the accelerator to maintain speed. If you let go of it the car will certainly decelerate quite rapidly and throw on the brake lights. Of course the grade of the hill will impact just how much decel you get, just as with say a manual car on a flat surface vs a hill.

At least that’s how both my EVs (both GM) have worked. Or if you don’t have one pedal turned on then it is similar to driving a regular automatic car. It will decelerate some since you’re not giving it any “gas” but based on the grade you will probably stay constant or speed up.

Personally I love one pedal driving and the amount of control it gives you. You can modulate speed so much better say while taking a turn without having to go between pedals. 

WilliamsSW > ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) 06/23/2020 at 18:14

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 Is that an adjustable drive mode maybe?  That's nice in city driving,  but would be annoying on the highway. 

ADabOfOppo; Gone Plaid (Instructables Can Be Confusable) > WilliamsSW 06/23/2020 at 18:38

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Depends on who made the car and how they have it programmed.

I haven’t driven a Tesla enough to speak to their system. But the Jag I-Pace and Audi E-Tron have adjustable modes so you can coast on the highway like a ICE car. There is always going to be more drag on a electric vehicle due to the motor/generators being the source of propulsion rather than petrol.

So even mild regen braking will feel more aggressive than simply coasting as that is how these cars recover energy. 

bhtooefr > GLiddy 06/23/2020 at 20:39

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So at least in Toyota hybrids that have a B mode instead of a low mode , the B mode will spin up the engine and dissipate excess energy there.

However, it’s much more frequent that a hybrid’s battery is completely full.

Additionally, most of Toyota’s regen braking is on the brake pedal. All of Tesla’s is on the accelerator, for the brake pedal to feel better. And, if for some reason regen is limited (usually either a cold battery, a hot battery/motor, or a full battery), it’ll indicate the reduced regen on the power meter in the instruments, so you just use friction braking to compensate, yourself.

PartyPooper2012 > For Sweden 06/24/2020 at 05:54

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Sooo... brake lights on? 

PartyPooper2012 > fintail 06/24/2020 at 05:57

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KillerAutoPilot

spielberg, are ya listening? 

PartyPooper2012 > ZHP Sparky, the 5th 06/24/2020 at 06:02

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pardon me. I am not familiar with tesla operation or one pedal driving mode. I have 3 pedals. I was just wondering... if there is a very steep downhill, what would tesla do to not... ummm... ride brakes.

Would it slow down to maintain original speed? Would is speed up as the weight of the vehicle pulled by gravity accelerated?

I was driving my wife’s MDX and I paddle shifted down to like 2nd or 3rd gear to not ride the brakes and it made me wonder what a fully electric car would do in that case. MDX was slowly speeding up as I was going further downhill and it gained speed, but being in a lower gear stopped it from being a runaway and i didnt ride the brakes. Just curious about teslas abilities in regard to maintaining speed.

ZHP Sparky, the 5th > PartyPooper2012 06/24/2020 at 11:27

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I think EVs are fundamentally different because they are almost always designed to recapture energy when not on the gas via “engine” braking without even using the brakes (this is why EVs go through brake pads very, very slowly in many cases). SO to answer your question they allow you some variability. With full on one-pedal driving mode (i.e. you can use the accelerator pretty much all the time to go from a stop, up to speed, and back to a stop - only needing brake pedal if you need to slow down faster than the car’s system is able to recapture energy) even on a steep downhill I would expect the car to slow down significantly if you take your foot off the gas. On a more “regular” mode the car will probably coast, or slow down somewhat. I wouldn’t expect it to turn in to a runaway train. But good question. Just by virtue of the engine braking designed in to these things to capture as much energy back in to the battery. 

fintail > PartyPooper2012 06/24/2020 at 12:51

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Not sure if Elon would embrace the product placement, or think it is more of the conspiracy against him and his perfect wonderful beautiful product.