UK cuts electric car subsidies.

[9873210]

As for 3 pedals - then I take it that a BEV with 'one pedal driving' making the brake pedal redundant as the car goes into regenerative braking when you stop accelerating, would be utterly unacceptable

Silly question (I hope ) - How do you do an emergency stop using regenerative braking?

Adrian

There are various levels of answers.

There's no real difference between a stop and an emergency stop.

As a driver you press the brake hard (or release the only pedal) and let the motor controller do it's thing.

As a hardware engineer you note that with proper motor control any motor can generate more torque against the direction of rotation than in the direction of rotation. The reason for this is that when braking resistive losses help rather than hurt.
This satisfies the criteria that you can stop faster than you can accelerate. If you have a spec for how rapidly you need to do an E-stop that would affect the sizing of the motor and motor controller (just as it would affect the sizing of brake pads).

As a software engineer you have the motor controller control the applied voltage so the AC current is a few Hz slower (for an induction motor) or a few degrees retarded (for a permanent magnet motor) than the rotor. The rotor is dragged towards the AC current which slows the rotor, and also increases the current, which means the motor controller needs to apply voltage opposing the current which is to say it operates as a generator.

As a mathematical physicist there is nothing different between acceleration and braking. There is no discontinuity, it's just that some of the variables smoothly change sign as you go from positive torque (motor) to negative torque (generator).

[JohnB]

They have brake pads!

[AF62]

I think you still need to open the bonnet on modern cars to put the fires out.

With a BEV if it catches fire then running in the opposite direction and not opening the bonnet would be a good idea.

And as for Spotify MP3 etc - all useless. Radio 4 is usual all I need with the occasional Radio 3. Actually, I do not normally have any music on in the car - it for listening to not wallpaper.

Of course Radio 4 programmes, but not Radio 4 where you are subject to the random whims of the schedule. Select the programmes that interest you and download them or stream them as podcasts or from BBC Sounds.

And all this stuff about talking to your satnav to get you home. What's the point of paying for that when I could just select "home" on Rita the Router on my Android phone.

Satnavs are not for directions as you can do that by reading signs, but for traffic, or rather the avoidance of.

One pedal? I didn't know that - like a bumper car?

Arb.

Bumper car - hopefully not, see the point above about not being anywhere near a BEV if it is on fire

As for 3 pedals - then I take it that a BEV with 'one pedal driving' making the brake pedal redundant as the car goes into regenerative braking when you stop accelerating, would be utterly unacceptable

Silly question (I hope ) - How do you do an emergency stop using regenerative braking?

Adrian

There is a brake pedal, it is just that with normal driving it doesn't get much use. Anyway lots/most modern cars, including BEVs, have an emergency braking system built in where if the car determines you are not going to stop before hitting whatever is in front then it will brake (and emergency brake) for you - and to be honest likely before you have even thought about it.

[dealtn]

As for 3 pedals - then I take it that a BEV with 'one pedal driving' making the brake pedal redundant as the car goes into regenerative braking when you stop accelerating, would be utterly unacceptable

Silly question (I hope ) - How do you do an emergency stop using regenerative braking?

Adrian

There are various levels of answers.

There's no real difference between a stop and an emergency stop.

As a driver you press the brake hard (or release the only pedal) and let the motor controller do it's thing.

As a hardware engineer you note that with proper motor control any motor can generate more torque against the direction of rotation than in the direction of rotation. The reason for this is that when braking resistive losses help rather than hurt.
This satisfies the criteria that you can stop faster than you can accelerate. If you have a spec for how rapidly you need to do an E-stop that would affect the sizing of the motor and motor controller (just as it would affect the sizing of brake pads).

As a software engineer you have the motor controller control the applied voltage so the AC current is a few Hz slower (for an induction motor) or a few degrees retarded (for a permanent magnet motor) than the rotor. The rotor is dragged towards the AC current which slows the rotor, and also increases the current, which means the motor controller needs to apply voltage opposing the current which is to say it operates as a generator.

As a mathematical physicist there is nothing different between acceleration and braking. There is no discontinuity, it's just that some of the variables smoothly change sign as you go from positive torque (motor) to negative torque (generator).

The real difference is the time taken to stop, surely.

So how, in practice, does the "car" know when I take my foot off that "one pedal" that what I want is an emergency stop braking, or a normal slow down braking?

[Arborbridge]

Silly question (I hope ) - How do you do an emergency stop using regenerative braking?

Adrian

There are various levels of answers.

There's no real difference between a stop and an emergency stop.

As a driver you press the brake hard (or release the only pedal) and let the motor controller do it's thing.

As a hardware engineer you note that with proper motor control any motor can generate more torque against the direction of rotation than in the direction of rotation. The reason for this is that when braking resistive losses help rather than hurt.
This satisfies the criteria that you can stop faster than you can accelerate. If you have a spec for how rapidly you need to do an E-stop that would affect the sizing of the motor and motor controller (just as it would affect the sizing of brake pads).

As a software engineer you have the motor controller control the applied voltage so the AC current is a few Hz slower (for an induction motor) or a few degrees retarded (for a permanent magnet motor) than the rotor. The rotor is dragged towards the AC current which slows the rotor, and also increases the current, which means the motor controller needs to apply voltage opposing the current which is to say it operates as a generator.

As a mathematical physicist there is nothing different between acceleration and braking. There is no discontinuity, it's just that some of the variables smoothly change sign as you go from positive torque (motor) to negative torque (generator).

The real difference is the time taken to stop, surely.

So how, in practice, does the "car" know when I take my foot off that "one pedal" that what I want is an emergency stop braking, or a normal slow down braking?

I share your concern - cars are getting truly weird. Some of the factors coming out in this discussion are quite a turn off rather than encouraging someone to buy.

Arb.

[Arborbridge]

Of course Radio 4 programmes, but not Radio 4 where you are subject to the random whims of the schedule. Select the programmes that interest you and download them or stream them as podcasts or from BBC Sounds.

Well, TBH I am not interested in downloading podcasts and I prefer the normal scheduling. The whole point for me is that I do not restrict myself to my own "whims" but I hear and learn about other things I would not have listened to. This can be particularly true of radio 3 when one discovers music one hadn't heard before.
In general, I am tired of people wanting the "have it now" on demand culture. I'd much prefer a random walk to see what is discovered - even in my DVD watching I have a list of films I know I'd like to see, but get them in random order. Predictability is sooo boring!

And all this stuff about talking to your satnav to get you home. What's the point of paying for that when I could just select "home" on Rita the Router on my Android phone.

Satnavs are not for directions as you can do that by reading signs, but for traffic, or rather the avoidance of.

Rita tells me the route and also gives an intication of traffic delays or hold ups. That does me just fine.

All in all, we have to conclude that you and I are on different wavelengths as regards motoring needs and preferences.

Arb.

[AF62]

Of course Radio 4 programmes, but not Radio 4 where you are subject to the random whims of the schedule. Select the programmes that interest you and download them or stream them as podcasts or from BBC Sounds.

Well, TBH I am not interested in downloading podcasts and I prefer the normal scheduling. The whole point for me is that I do not restrict myself to my own "whims" but I hear and learn about other things I would not have listened to. This can be particularly true of radio 3 when one discovers music one hadn't heard before.
In general, I am tired of people wanting the "have it now" on demand culture. I'd much prefer a random walk to see what is discovered - even in my DVD watching I have a list of films I know I'd like to see, but get them in random order. Predictability is sooo boring!

Yes there is a risk of only listening and watching what you are familiar with, but personally with podcasts and streaming tv I have listened and watched things that I would never have thought would have interested me from broadcast radio or tv.

What podcasts are particularly good for is the 'long form' type of interview that would never be given the space on radio.

All in all, we have to conclude that you and I are on different wavelengths as regards motoring needs and preferences.

Arb.

Life would be boring if everyone was the same

[Mike4]

I receive R4 out and about using the "BBC Sounds" app my iPhone, and the phone connects and broadcasts through the van hi-fi automatically by bluetooth as soon as I get in and turn the ignition key. Superb functionality from the app, far better than the DAB radio built into the van hifi.

The iPhone also has a truly excellent satnav, the main use being to guide me through the local roads to my destination address which is different every day. For route planning between cities it is OK, but sometimes my Mk 1 brain cell is better.

[Arborbridge]

What podcasts are particularly good for is the 'long form' type of interview that would never be given the space on radio.

I agree with that: it's just that I have good intentions but never actually listen to any!

[Arborbridge]

I receive R4 out and about using the "BBC Sounds" app my iPhone, and the phone connects and broadcasts through the van hi-fi automatically by bluetooth as soon as I get in and turn the ignition key. Superb functionality from the app, far better than the DAB radio built into the van hifi.

The iPhone also has a truly excellent satnav, the main use being to guide me through the local roads to my destination address which is different every day. For route planning between cities it is OK, but sometimes my Mk 1 brain cell is better.

The route planning is fine, except that sometimes one wants to go on a particular route not because it's efficient, but because you want to go there.

I am very reluctant to use re-routing due to hold ups. I always check for massive ones, but I've known occasions when it's been a pointless exercise: better to sit in the queue.

Arb.

[Mike4]

I am very reluctant to use re-routing due to hold ups. I always check for massive ones, but I've known occasions when it's been a pointless exercise: better to sit in the queue.

I find this too. Driving typically 30k miles a year I often run into holdups from accidents etc, and I've learned if I decide to re-route, the obvious alternative route will usually be jammed solid too, from other drivers choosing it. So any re-route needs to be designed to avoid the obvious alternative route. If there is no second or third level of re-route to choose, stay in the primary jam and just wait.

[Howard]

So how, in practice, does the "car" know when I take my foot off that "one pedal" that what I want is an emergency stop braking, or a normal slow down braking?

I can answer your question for the KIA.

The attraction of the car for me is that it is very similar to ICE cars which I drive (have driven).

If I need to brake hard I just put my foot down hard on the brake pedal.

The wipers, lights, heater, aircon etc are all controlled in a very similar way to other cars using stalks and buttons. Nothing fancy.

However in normal driving the car will seamlessly recharge its battery when it slows down. I can, if I want to, change the amount of recharging which occurs when decelerating. If I set this higher, (which is easily done), then the car slows down more depending on how much I take my foot off the accelerator. The only reason for doing this is to increase the range of the car and, apparently in city driving it will go for the claimed 280 miles before needing recharging - but I haven't tested this.

Mrs H doesn't bother changing the charging rate so she just gets in and drives. The car behaves the same as our previous automatic Golf. (ie push accelerator to go faster and brake to go slower/stop).

regards

Howard

[dealtn]

So how, in practice, does the "car" know when I take my foot off that "one pedal" that what I want is an emergency stop braking, or a normal slow down braking?

I can answer your question for the KIA.

Not really, as you aren't describing the situation above where there is claimed to be a single pedal (that acts as an accelerator when depressed but a brake when released - presumably).

[swill453]

Not really, as you aren't describing the situation above where there is claimed to be a single pedal (that acts as an accelerator when depressed but a brake when released - presumably).

I don't believe such a thing exists.

Someone referred to "one pedal driving", not to a BEV that had one physical pedal.

Scott.

[Mike4]

I too am wondering about this 'emergency stop' thing that someone suggested happens if you take your foot right off the go pedal.

When I do an emergency stop I find the anti-lock system kicks in and cadence braking almost locks the wheels intermittently but prevents full lock-up, thereby allowing maximum deceleration whilst maintaining the ability to steer. Quite violent when it happens.

Do electric cars have cadence/anti-lock braking during fierce electric braking? Or does one have to use the stop pedal to get that?

[Howard]

So how, in practice, does the "car" know when I take my foot off that "one pedal" that what I want is an emergency stop braking, or a normal slow down braking?

I can answer your question for the KIA.

Not really, as you aren't describing the situation above where there is claimed to be a single pedal (that acts as an accelerator when depressed but a brake when released - presumably).

I will attempt to answer your question.

I've driven both a Leaf and a KIA BEV. For both, if the driver wants to, one can set the recharge level so high that one can drive the car in most circumstances, but not all, using only the accelerator pedal. So if the traffic in front slows down significantly or, say, one is driving up to a roundabout on a fast road, then taking ones foot right off the accelerator causes the car to brake hard using the electric motor and producing a very significant but short-lived charging boost to the battery. If the driver wants by taking his/her foot completely off the accelerator, this will bring the car to a complete stop.

Speaking personally, whilst I find that "one pedal" setting quite interesting and easy to master, I prefer to set the recharge level lower or, driving today, left the car to set the level automatically. It does this using radar or something similar and watches the traffic in front. When I wanted to brake a little harder, I used the brake pedal in the normal way. And, of course, it cleverly actually slows the car mainly by regeneration unless one brakes very hard when the disc brakes are used. It was very similar to driving my petrol engined car where I tend to try to anticipate the road situation ahead and decelerate before needing to brake, thus getting good fuel consumption.

So the Leaf or KIA BEV is partly controlled by a computer and, just like my desktop, can be set in hundreds of different ways to suit its "driver". I guess most drivers will work out the best setting for their driving style and then not bother with too many variations. Just like I don't use most of the hundred fonts on my PC.

And, of course, like BEVS, both the petrol Golf we traded in and my ICE car, like virtually all fairly new cars, have the emergency braking systems which are computer controlled and, in an emergency/potential crash situation (decided by the computer, not the driver) will slam on the brakes whether the driver reacts or not. These days, I believe all cars, diesel, petrol etc have these computer-controlled safety systems and they can't be turned off.

And, as a bonus, answering Mike's question, above, about emergency braking in wet conditions, BEVs have "normal" disc brakes and they will act in the same way as any other cars disc brakes in this situation. But to be honest I haven't personally tested emergency braking in Mrs H's shiny new car.

Hope this is helpful.

regards

Howard

[dealtn]

I can answer your question for the KIA.

Not really, as you aren't describing the situation above where there is claimed to be a single pedal (that acts as an accelerator when depressed but a brake when released - presumably).

And, of course, like BEVS, both the petrol Golf we traded in and my ICE car, like virtually all fairly new cars, have the emergency braking systems which are computer controlled and, in an emergency/potential crash situation (decided by the computer, not the driver) will slam on the brakes whether the driver reacts or not. These days, I believe all cars, diesel, petrol etc have these computer-controlled safety systems and they can't be turned off.

Well I didn't know that, but just confirms, regardless of being an ICE, BEV (or some other TLA), or whetehr it is "one-pedal", "three-pedal" (or "seventeen pedal"), this "emergency stop braking" has nothing to do with car type, or the energy source that powers it. So irrelevant to the thread, and the claims made earlier about it then?

[AF62]

And, as a bonus, answering Mike's question, above, about emergency braking in wet conditions, BEVs have "normal" disc brakes and they will act in the same way as any other cars disc brakes in this situation.

VW's new ID.4 BEV is using drum brakes on the rear because they have a lower rolling resistance than disc brakes (https://www.thedrive.com/news/36683/why ... rum-brakes) and they have a 150,000 km service interval (https://www.continental.com/en/press/pr ... d-3-236814).

[Howard]

And, as a bonus, answering Mike's question, above, about emergency braking in wet conditions, BEVs have "normal" disc brakes and they will act in the same way as any other cars disc brakes in this situation.

VW's new ID.4 BEV is using drum brakes on the rear because they have a lower rolling resistance than disc brakes (https://www.thedrive.com/news/36683/why ... rum-brakes) and they have a 150,000 km service interval (https://www.continental.com/en/press/pr ... d-3-236814).

I think that, in answer to Mike's question the ID.4's front disc brakes will do the cadence braking. Do you think drum brakes can do this?

In an emergency braking situation, I believe that as the weight of the car bears down on the front, it's the front disc brakes that are critical?

regards

Howard

[AF62]

And, as a bonus, answering Mike's question, above, about emergency braking in wet conditions, BEVs have "normal" disc brakes and they will act in the same way as any other cars disc brakes in this situation.

VW's new ID.4 BEV is using drum brakes on the rear because they have a lower rolling resistance than disc brakes (https://www.thedrive.com/news/36683/why ... rum-brakes) and they have a 150,000 km service interval (https://www.continental.com/en/press/pr ... d-3-236814).

I think that, in answer to Mike's question the ID.4's front disc brakes will do the cadence braking. Do you think drum brakes can do this?

In an emergency braking situation, I believe that as the weight of the car bears down on the front, it's the front disc brakes that are critical?

regards

Howard

Not disagreeing at all. I was just pointing out that a lot of people had been surprised VW had moved from the modern standard of ‘discs all around’ back to the 80s ‘discs at the front, drums at the rear’ and that decision had been made to increase the range of the EV.