Full stop in low

5555 Views 39 Replies 23 Participants Last post by marcusm, Nov 30, 2017

marcusm

Discussion Starter · Nov 25, 2017

I really wish that they would reprogram or offer a software update to have the Volt come to a full stop using regen rather than creep in low. The creep although doing exactly what it is designed to do —- mimic a gas automatic transmission— is irritating in this car and my leg gets tired of the brake pedal, which given the strong regen and the regen paddle I really only use now otherwise for sudden stops. Since they apparently implemented this in the Bolt in low, I assume there is no hardware related reason they couldn’t have that code deployed in the Volt? Really wish they did...

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Arcanox

· #5 · Nov 25, 2017

Holding the regen paddle won't cancel creep; you get down to about 1-2 MPH and then it "lets go" of regen and starts creeping again, up to about 3 MPH in L or 5 MPH in D.

I would love for them to program an option to disable creep and enable one-pedal driving in L. It's a matter of getting their firmware developers to write it; they're probably focusing on other things sadly.

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Arcanox

· #9 · Nov 26, 2017

wordptom said:
Regenerative braking uses the car’s kinetic energy to crank the generator, which can recharge the battery while braking the car. It can’t hold the car at a complete stop because there’s no regen when the car’s not moving. Engineering the vehicle to "creep" or not to "creep" once it’s stopped is a separate issue.

The Bolt consumes a small amount of energy to slow down the car and hold it at a stop once regen becomes ineffective when using "single-pedal driving". It'll use a microscopic amount of the energy you recovered from the actual regen to do this, so it's not entirely wasteful, but I'm sure it does shorten the range a tiny bit compared to using the brake pedal at low speeds.

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Arcanox

· #13 · Nov 26, 2017

quirkySquirt said:
I always thought of the Volt line as a gateway EV and thought the lack of full stop on REGEN (paddle or L) was on purpose so users wouldn't get caught off guard with lack of creep (assuming most drivers came from an automatic ICE).

I'm also not a huge fan of the full-stop via paddle or L since you're not actually applying the brakes. I don't have a good rationale, but having my brake applied at a full stop always felt safer. On the Bolt I actually miss the creep of the Volt when using the paddle. It's a good reminder when I come to a full stop that others behind may not know I'm stopped (no brake lights). True, it's the people behind me that are responsible for judging distance to me, but the brake lights help them out immensely.

I agree that the brake lights are strange, but when I've seen i3s driving around, the brake lights only turn off once they're almost completely stopped. At such a low speed, the person in the rear would have to be very distracted to rear-end the car and the brake lights may or may not make a difference

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Arcanox

· #24 · Nov 27, 2017 (Edited)

telveer said:
While a full stop may be practical in a BEV because there is just one motor, the Volt has a separate traction and generator motor. The generator is only 55kW. Volt has to constantly switch between these motors as the vehicle decelerates/accelerates. So, the regen system is significantly different from Bolt, and not a simple software update.

It doesn't constantly switch between them; they both work in unison and are both permanently connected to the output shaft through two planetary gearsets.

Barrydr said:
It would be nice if GM would have the brake lights come on with the use of the regen paddle. Otherwise, I'm fine with the way it functions and don't mind lifting my foot to the brake if needed. Just my 2 cents.

The brake lights do come on when using L or the paddle.

wordptom said:
If MGB is the primary traction motor/generator and MGA is the motor/generator used to extend the Volt’s range by generating electricity when clutched to the gas engine, it would be impractical to use MGA for regenerative braking. That would require clutching it to the drivetrain whenever you took your foot off the accelerator (unless you immediately shifted into N), even in Electric Mode, even if you were moving slowly.

My understanding is that MGB, the primary traction motor, is used for regenerative braking.

MGA and MGB are both always connected to the output shaft, and two clutches in the transmission hold different parts together or hold them to the chassis so that certain parts remain still, causing power to be transferred through different paths. MGB is the only one used for regenerative braking, and MGA is the only one used to generate power from the ICE, but both can provide tractive effort. MGA also starts the ICE.

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