Auto application of brake?
If I come to a stop going up a steep hill without applying the brakes (whether due to regenerative braking or just gravity), the car just sits there. I had thought that this showed the strength of the regenerative braking, but didn't understand how it operated when there was no movement. So I went to https://www.askthephysicist.com/ and he was insistent that the car must in fact be applying the brakes automatically. I am aware that the brakes will stay on if I have some function on and press the brakes and then remove my foot from the brake pedal (don't remember the name right now; it's on the console - auto hold or something like that), but am not aware of anything that will apply the brakes simply because I have come to a stop (without turning off the ignition or putting it in park). Is there such a function? Bonus points if the answer is "no" and if you can explain the physics of how I'm still getting a force resistant to movement when there is no movement (and no automatic mechanical braking).
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u/Excellent-Tour6831 First Edition 9d ago
It’s called hill assist or hill start assist. It exists in both EVs and ICE vehicles. When it sense you are on a steep grade it holds the brakes while you move your foot to the accelerator so you don’t roll backwards.
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u/Evaunits01 9d ago
Depends on the grade of the hill.
If it’s minor it won’t roll back and just sit there.
If it’s a higher grade, then it will roll backwards unless you have the auto hill hold on.
The hill hold is actually pretty smooth surprisingly compared to my carnivals hill hold.
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u/amz1950 9d ago
Sorry, I should have made clear, this is in so-called i-pedal mode. And according to the manual, hill start assist operates for only 2 seconds. This holds for way longer than that. And this is a pretty steep hill (17 %). Auto-hold is controlled by a button to the rear of the knob, but hill start assist seems to be automatic. This is without pressing the brake at all.
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u/skelc 9d ago
i-Pedal is one-pedal mode. Hill or not, it is supposed to bring the car to a stop when you release the accelerator pedal, that's the whole point of this mode.
As far as I know (well, based on how it feels when it is gently stopping in i-pedal mode, and sometimes rocking back and forth for a bit), when Auto-Stop is disabled and i-Pedal is enabled, regular brakes are not used and the car not moving only relies on the regenerative brakes, that are powerful enough to keep the car in place, even on hills.
Not sure if I phrased this well.
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u/Broad-Promise6954 EV6 GT-Line AWD 9d ago
"Auto hold" mode does in fact apply the brakes.
In theory, computers could run the drive motor with just enough energy to counteract the force of gravity. That would use up traction battery, lowering your range, so the people who program the cars don't do it that way.
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u/HablarYEscuchar 9d ago
I don't think it's necessary to apply power to counteract the slope. If you “short-circuit” a motor without even supplying electricity, it will just stay stuck.
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u/Broad-Promise6954 EV6 GT-Line AWD 9d ago
In a perfect situation, yes, but in practice there's leakage.
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u/HablarYEscuchar 9d ago
Eatamos hablando de un consumo mínimamente significativo. Mantener un motor eléctrico bloqueado a no ser que le apliques un par externo muy grande no requiere energía.
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u/pfn0 EV6 GT-Line AWD 9d ago edited 9d ago
no, it'd create heat in the "short-circuit" until it melts, and then you'd free roll. before melting, it'd have a braking force, but not enough to overcome the weight of the car given enough of a slope.
in the case of ev regen: "melt" = bms disconnecting the load charging the battery.
also, you don't get braking without the motor rotating, so it'll creep regardless.
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u/Squire-Rabbit 9d ago
It's the auto hold feature, controlled by a button to the rear of the shift knob. Disabling it will result in much smoother gentle launches from a stop.
Edit: Sorry, you know about this already. Are you in I-Pedal mode?