When to use electric park brake?

[kpetrov]

If the car is stationery but in Drive with the handbrake on and you switch to Neutral the drive releases and the car rocks back as the power to the wheels is removed.

That's mean your handbrake don't work and you are doing the experiment on a slope.

As your previous post demonstrates by your own action - this is not true! If still in Drive the electric motors are trying to turn when braked, however when you move to Neutral the transmission "wind-up" (for want of a better term) releases and the car rock backs slightly without turning the wheels - simples!

So you are trying to tell me that while braking in any situation the vehicle is trying all the time to overcome it and fight it by continuously providing power to the el. motors!?
Let's say while driving in B0 the driver start to press on the brakes slightly and regenerative braking is activated... are you saying that power to the el. motors will be provided in the same time?
You can do the following experiment... while on D with brakes pressed step slightly on the accelerator pedal in order to really provide some power to the el.motors. Then you will feel the rocking motion. Cause if still in D and on brakes switching to N doesn't produce even the slightest rocking motion on MY2018.

 

[greendwarf]

Now you are just trolling me - I specifically said when stationery with the handbrake applied :roll:

 

[kpetrov]

Not trolling you just trying to provoke a discussion regarding the reasoning why when in motion they (the designers) can cut the power to the el. motors but when stationary it is not done and power is constantly fed to the el. motors without a reason.

 

[littlescrote]

It's not done without a reason, it's done like that to mimic the creep of a traditional auto vehicle. If you're in Drive with your foot lightly on the brake there is still power going to the motors which you can see on the power flow and feel by allowing the vehicle to creep more or less which is proportional to brake pedal pressure. A harder press of the pedal then cuts the power completely rather than just hold the physical brakes against motor output which would obviously be wasteful. All of this behaviour is easy to see on the dash display. You are either being purposely obtuse, or misunderstanding something.

 

[kpetrov]

The first small stroke of the brake pedal is activating regenerative braking. If the speed is low enough (almost stationary) regenerative braking is not working and the vehicle continue to supply power to the el. motors while you are initiating very gentle brake.
I never said that not to be the case and you can obviously see it on the dash.

Probably I didn't understand what you are saying but what I get is:
You have said before that while stationary on brakes the vehicle is constantly feeding el power to the motors (fighting against brakes).

I specifically said when stationery with the handbrake applied

Now you are saying harder brake press cut the power completely rather than just hold the physical brakes against motor output. What it is finally!?
If the vehicle is stationary the brake was pressed enough to cut the power. What is considered hard brake press is irrelevant then.

 

[ThudnBlundr]

While stationary with my foot on the brake, no power is going to the electric motors. I can see it on the dash and selecting neutral has no effect.

Why on earth would the designers program a car to waste power? :roll: They have programmed it to start supplying power when the brake pedal is released enough to mimic creep, but only an idiot would program the car to run the motors against the foot brake when it's pressed hard enough - for one thing, all that energy would have to go somewhere and it would simply heat up the motors needlessly.

 

[greendwarf]

At the risk of venturing into the bear pit again :lol: perhaps this a result of auto drivers being too lazy to apply the handbrake when stationery. In a non-auto if you don't put it into neutral the car will stall but an auto doesn't - hence the creep.

However, in the PHEV in B0 with no pressure on the accelerator there is still power supplied to the motors to prevent drag when coasting. Perhaps you can't remove that low power input unless neutral is engaged or in park.

I only notice it when stationary I.e. no acceleration "in gear". So either I have to press the brake pedal or use the handbrake (NB. my 2014 car doesn't have the electric parking brake on later models which might act differently) as I described.

 

[kpetrov]

However, in the PHEV in B0 with no pressure on the accelerator there is still power supplied to the motors to prevent drag when coasting. Perhaps you can't remove that low power input unless neutral is engaged or in park.

I personally acknowledged in my previous posts the power supplied to the motors to prevent drag when coasting but when stationary on brakes that power is no longer needed and it is not supplied.

Of course if you want to keep staying stationary you have to stay on the brakes or parking brake. Once you release the brake then the the power is fed and vehicle starts moving.

 

[greendwarf]

Well we are just going to have to disagree. You might be right about your later US model with an electronic parking brake but you are wrong about my 2014 UK model with a manual handbrake - power is still fed to the motors in Drive with the handbrake on, fact! :roll:

 

[ThudnBlundr]

It does it in our 2015 (manual handbrake) model too. The only way I've found to cut power to the motors is to use the footbrake (or put it in neutral of course).

 

[kpetrov]

Well I agree with the manual handbrake comment.
It is designed to be used after the vehicle is off or in P anyway. You guys can use it for drifting at least.

 

[greendwarf]

Not in the UK, at least - the Highway Code mandates use of the handbrake when stationary e.g. at traffic lights. You could fail your driving test if you don't.

 

[jaapv]

Doesn't a transmission brake - like "P" count? I wonder what percentage of drivers comply...

 

[ChrisMiller]

The Highway Code doesn't really recognise technology much later than the 1950s. For example, stopping distances appear to be based on a Ford Prefect with two-inch wide cross-ply tyres and drum brakes. See also: parking space dimensions. :lol:

 

[jaapv]

Well, I tested it today. The electric handbrake cuts off the motors. If you hold the car by the footbrake against creep and then apply the handbrake it will rock after a split second