EV braking

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Paul1970
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Post by Paul1970 »

Dumb question possibly, but given that the only electric car I have been in was a bumper car, do EV vehicles stop almost instantly once you take your foot of the accelerator?
Something I was reading had me wonder that if this was the case then there would be little or no brake light warning to a following vehicle which would be quite dangerous. Or do they still require similar stopping distances of traditional cars?


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johnd
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Post by johnd »

No they don't stop instantly! The latest EV's like the Jaguar I-Pace have two types of braking:

1. Traditional friction brakes - essentially the same and probably as effective as on eg a Macan;

2. Regenerative braking via the electric motors, which I guess is more what you're thinking of. The driver can usually set what level of regen they wish to use, often two levels: moderate and stronger.

Jaguar say for the i-Pace that each mode (which can obviously be used at the same time) can typically generate 0.2g of braking, for 0.4g max. I don't know exactly how this compares to eg Macan or whether the 0.2g friction braking is typical hard braking or emergency stop - conceivably the latter is >0.2g.

If you have the stronger regen set then apparently it's perfectly possible to use a one-pedal driving style, ie the regen provides all the braking you normally need. I don't know but at a guess anything more than a minimal regen braking would also also show on the brake lights - that ought to be totally trivial to do.
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Ian.g
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Post by Ian.g »

It will still be subject to the level of grip/friction between the tyres and the road so I doubt it will be as good as the Macan. Certainly not better. It is possible to skid a car by slowing the wheels down with the gearbox as I have previously discovered on snow/ice. The same will be true of the road if you try hard enough.
Retired
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Post by Retired »

Try to push the brake pedal through the floor and you'll get a stop of around 1g. A bit more with a dry grippy surface and less if the road is shiny wet.
etc.

Max lateral acceleration is also around the 1g figure for a sporty car on a good surface.
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ScotMac
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Post by ScotMac »

I've only had a test drive of a Tesla and braking is very "different" as it recharges the batteries.

You would like to think any sudden stopping would activate the brake lights - but not sure.
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Post by Deleted User 1874 »

My Tesla has two levels of regenerative braking when you lift off the accelerator. Low level drives much like a conventional car and high level gives a much stronger braking force, effectively making it a one pedal car for most normal driving. It's very intuitive once you adjust to it (it is different to conventional engine braking) and you hardly ever have to use the brake pedal. The brake lights do come on with regenerative braking too.
MacanArif
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Post by MacanArif »

Peteski wrote: Sat Apr 21, 2018 2:45 pm My Tesla has two levels of regenerative braking when you lift off the accelerator. Low level drives much like a conventional car and high level gives a much stronger braking force, effectively making it a one pedal car for most normal driving. It's very intuitive once you adjust to it (it is different to conventional engine braking) and you hardly ever have to use the brake pedal. The brake lights do come on with regenerative braking too.
I have a BMW i3 and as you say it's a one pedal car due to the extra regenerative braking which slows down the car as soon as you come of the pedal. And yes the brake lights do come on as soon as you take the foot of the accelerator, I've tested it in the dark.
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N13LXC
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Post by N13LXC »

The braking on my c350e was bizarre. Effectively off throttle, you were always an ev, low rate deceleration was done through regen to a point, then friction for the rest/ heavier deceleration. The cutover was noticeable and in my mind slightly dangerous. E.g. when approaching roundabouts with no intention of stopping, the car would be in a weird state of electric off and engine off leading to a delayed pickup in acceleration.

You get used to it though...
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