OT: Brakes seizing on electric cars? (2024 Update)

[NY]

Maybe I will, if I can do it with a straight face. I intend to keep my diesel car for as long as I can, because electric cars have not yet progressed to the state that can provide the same usability, in terms of range and (even more important) refuelling time. I mostly do short journeys in my car, which would ideally suit an electric car, but I want a car that at a moment's notice can drive a long way, in one go (apart from a brief loo stop). I don't want to have to make an enforced stop for an hour or so to get me enough range to complete my journey, and I don't want to have to search for a recharging station. When I don't have to plan a longer journey like a military exercise, factoring in recharge stops when travelling around on a day out, then I might buy one. My diesel is 15 years old and has done

190,000 miles. I'm hoping I can keep it going for a lot longer, and more importantly we can keep my wife's newer diesel going even longer, and just accept that when my cars dies and has to be replaced with an electric, we can manage on just the one car (hers) that is free of the range/recharge restrictions.

I do wonder how the country's electrical infrastructure is going to cope after 2030 when no new IC cars are sold and gradually more and more electricity is needed for electric cars. Will the HV and mains wiring cope, and will we have enough generating capacity, especially at night when there's no solar, to charge cars overnight. Overnight charging can be done at a lower rate because within reason you don't mind how long it takes as long as you can rely 100% on your car being full for the drive to work in the morning.

I imagine generation profiles will change: instead of a large demand during the day, a "cooking surge" in the early evening and little demand overnight, it will probably become more constant, with some charging demand as everyone gets to work and charges for the journey home again, and then a huge increase in demand at 7 PM or thereabouts as everyone gets home from work, puts their cars "to bed", on charge, and the intelligent charging algorithms manage the demand so as to level it out throughout the night.

Intuitively, it "feels" counter-intuitive that braking force decreases as speed increases. I presume this means that you use your friction brakes most at high speed (for times when you need to slow down quickly) and at very slow speed. Maybe braking force is proportional to speed as long as you allow the power to increase without any limit. I can understand braking force being limited artificially by the rate at which you can dissipate the heat.

Did you find that you adjusted fairly quickly to regen braking on the accelerator - does it "feel" the same as the retardation you'd get in an IC car when you lifted off the power, or do you find you need to keep your foot on the accelerator in situations where you'd be able to lift off in an IC car for a brief break (break. not brake!) during level or slight descent?

I wish manufacturers hadn't made (some) electric cars with one-pedal driving. I like to have one pedal that controls power, with limited, predictable retardation due to friction and air resistance, and a totally separate pedal that controls braking (whether it be frictional or regen). I like to be able to lift my foot right off the accelerator at times such as a very gentle downhill, and not have to keep my foot permanently on the accelerator to avoid regeneration.

I've just bought a ride-on mower and I still haven't got used to its single-pedal operation: the engine runs at a constant speed and the forward and backward pedals control the hydraulic transmission. But as soon as you come off the pedal, the thing stops very quickly. I still find myself instinctive pressing the brake (left-foot on the mower); for me, left-foot braking is easier to get used to (though something I would NEVER do in an automatic car) than single-pedal braking.

[nib]

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Well at the moment you are in luck, because most if not all EVs have some sort of option to make them feel more like an ICE car. Although I think Tesla on some recent cars may have moved away from that.

But the point is that EVs (and hybrids) are different, they can recover kinetic energy and to maximise that recovery it's necessary to drive them slightly differently. Newer ones are probably better, but on mine that means thinking ahead and starting to slow down earlier. Having all regen on the accelerator and having friction come on only with the brake pedal is just what you need for immediate feedback that you are doing it properly: if you have to touch the brake pedal before you are almost at rest you have failed!

nib

[Commander Kinsey]

Still can't work out what "see just how often you will be mashing that brake pedal" means. The answer would be the same as a normal car, if set to behave like one. I think that's how I'd set it, so I can let go of the accelerator to ease off speed very slightly when speeds change on a motorway without having to change pedal.

That resistor, why not just turn the volume up on the stereo?

[Brian]

The idea that electric cars use conventional brakes in a fundamentally different way is flawed based on my experience of driving a hybrid - including in EV mode.

True, you use the brakes less- at least you should aim to - but you still use them. If anything, regenerative braking is perhaps a misleading term.

Take leaving a motorway. In a conventional car, you would typically reduce speed on the slip road, changing done as you go etc ( how I was taught), finally, coming to a stop if needed using the brakes at any signal, sign etc. In an EV ( or hybrid) the drive to the wheels is stopped - you are essentially coasting- the turning wheels drive the motors as generators and charge the batteries.

Likewise, on a long hill descent, where you might engage a low gear, a the same process is invoked as above.

That said, the ‘top up’ from a single instant is marginal. I can only recall seeing an increase in range after a long hill descents. That said, I get ( about) 1/3 mile / kWhr and the display is in miles.

Plus, of course, if you need to stop / slow down quickly, you need the brakes.

[nib]

You can do that. Most people seem to choose not to, the 1-pedal mode with a lot of deceleration without using the brake pedal is actually a very nice way to drive.

BTW, I don't think any EVs use resistive braking. If the battery is full or too cold to accept a high charge you get less braking effect, so you use the brake pedal sooner. Some Teslas hide that by automatically adding a bit of friction brake into 1-pedal mode.

EVs are not constrained by the century-old technology legacy of ICE cars. They don't have to emulate them if there's a better way.

nib

[nib]

When I leave a motorway, I start decelerating typically just about the start of the slip and again typically I have to use the brake pedal just before I come to a stop at the top, if I have to. If the way is clear, I'd typically not need the brake pedal at all.

As an order of magnitude, stopping from motorway speed all on regen gets you about 500 metres of extra range.

We have a PHEV too, which drives the same way but has a smaller battery and doesn't get quite so much regen effect as the EV; you need to start slowing earlier to get full effect.

I've seen the range figure go up on a stop, but not often.

nib

[Commander Kinsey]

What a weird way of thinking of it. I think of kinetic energy = 0.5mv^2. The v^2 being important. You have to take more energy out of the vehicle to lower it by the same number of mph at higher speeds.

Then it's badly made. It should adjust as you slow down so the same pedal movement is removing x mph per second, just as a friction brake does. Otherwise you're going to find yourself braking from 70mph, then realising you're slowing a hell of a lot quicker near the end, and the guy behind you with friction brakes slams into you as you stop unexpectedly fast.

Sounds like they need better regen in the car, so we don't have to think of such things. All brake use should be regen, no matter what the conditions.

One day they'll invent a battery that does what you ask of it.

[Commander Kinsey]

No it isn't. It means you can brake without meaning to. Speeding up and slowing down are two very different actions and should have seperate controls, I'm surprised it passes safety laws.

If it isn't automatic it's very very dangerous, so you don't know how much braking you'll get? Wow.

ICE is in car entertainment, please don't re-use acronyms.

Petrol cars aren't constrained either. Fly by wire isn't a new thing.

[NY]

I passed my normal test in 1981 and my instructor was a retired police Class

1 driving instructor so he taught the police to drive to the principles in Roadcraft. He told me after I'd passed my test that it was very difficult when he started teaching the public for the normal test, because some things that were required for the normal test were diametrically opposite to how he drove and how he taught the police to drive.

The main one was the requirement to change down sequentially through the gears when coming to halt or near-halt at a junction (*). Advanced drivers (as I found when I took my IAM test in 1991) do it differently. As long as you're not going down a steep hill, stay in the gear that you were in before you started braking (eg 4th/5th/6th) and remain in that gear as you brake progressively (**). Once you reach the no/no-go decision point, change directly into the correct gear to accelerate away (eg 2nd/3rd if the junction is clear) or press the clutch and hold it down while go you into

1st and wait for a gap (***). This technique took a bit of unlearning/relearning, but it is now second nature.

That technique is taught/required nowadays for the normal test as well, according to my nephews who each passed in the last 10 years.

(*) My mum had IAM lessons, though she never actually took her test, in the

1970s, and I can remember her commenting on how the IAM didn't want people changing down sequentially.

(**) Progressive braking is an interesting one to learn. Instead of jamming your foot on the footbrake at high speed and keeping the same braking force throughout, you start with gentle braking, gradually increasing the braking force as the speed drops, and then reduce the braking force almost to the point of no brake just before you come to rest (and then apply the footbrake and/or handbrake once you are stopped!): this means that there is no sudden deceleration from high speed, and no lurch to a sudden halt.

(***) And if it looks as if you will need to wait for more than a few seconds, go into neutral to lessen the chance of lurching forward if your clutch foot gets tired (rare) or if you are hit from behind (very rare!) and then be ready to go into 1st just before you need to set off. Also, once you are safely stopped, use the *handbrake* to stay stopped, *never* the footbrake because the latter is rude to drivers behind at night as it will dazzle them, especially now cars have in in-your-face high-level brake light.

[SH]

I beg to differ, ICE is Internal Combustion Engine..... which covers both diesel and petrol engines and obviously EV is Electric Vehicle.

[SH]

This is interesting as I have an automatic direct shift 6 speed gearbox that has 2 clutches (1st for even numbered gears and the 2nd for odd numbered gears)

The box changes down sequentially when I apply the brakes, it does not stay in the current gear and then go straight into the appropriate gear when I then put my foot onto teh accelerator.

Equally, you are not told to stay in the current gear when accelerating and then shuft into the correct gear for the new speed you have decided to travel at.

[NY]

I am surprised too, but then I'm also surprised that cars are allowed to have indicator lights which are placed very close to bright lights such as headlights or brake lights which means that they are almost invisible when those lights are on. At least DRLs dim on one side when the indicator is on (that's often more noticeable that the flashing of a very faint indicator, if the sun is reflecting off the indicator "glass"!). A "triumph" of design over usability.

Single pedal works well when you are moving at very slow speed and want to be able to stop very quickly and precisely. My ride-on lawn mower has it for its forward and reverse pedals (separate pedals on RHS), even though it also has a supplementary pedal on LHS for brake - more of a foot-operated parking brake.

But for driving at normal speed where you want to have more control over the retardation during the course of the braking, I imagine it is a real pain because it means you need to keep your foot on the accelerator/brake pedal all the time, and can't remove to foot to rest it for a second, or to slow down very gradually by air resistance and engine compressions only. I would imagine it requires a fairly radical change to the way you drive, rather like the revolutionary UI changes between Windows 7 and older versus Windows

8 and newer. "Visible" change (ie to the way you use a tool) should be evolutionary, if at all, even if there are all sorts of "invisible" changes under the bonnet..

[nib]

It's the way it is!

The battery is able to absorb only a certain amount of power. So it can't take enough for a high rate of deceleration at high speeds.

To take out a certain a amount of kinetic energy requires the speed to reduce by a smaller amount the higher the speed (as you say). So the regen braking can produce a bigger change in speed at lower speeds.

Take some numbers. Suppose a 1500 kg vehicle and a maximum 30 kW rate of absorption by the battery, so 30,000 joules/second max (a small basic EV).

At 30 metres/second (about 67 mi/h) the kinetic energy is 0.5mv^2 = 675 kJ. After 1 second of braking at 30 kW, the energy left is 675 - 30 = 645 kJ, so the speed has come down to 29.3 m/s, so we have lost 0.7 m/s in 1 second (about 1.5 mi/h/s deceleration).

Now come down to 20 m/s (about 45 mi/h), the kinetic energy is 300 kJ. 1 second of regen braking would bring that down to 270 kJ, so 19 m/s and a reduction of 1 m/s (about 2.2 mi/h/s).

At 10 m/s (about 22 mi/h), the energy goes 75 kJ to 45 kJ, the speed comes down to 7.7 m/s, a reduction of 2.3 m/s (about 5.1 mi/h/s).

So the braking rate in terms of rate of loss of speed is just over three times as large at 22 mi/h as it is at 67 mi/h. That's just the physics of regeneration given a limited rate of current into the battery.

Yes it's different, but it's something you very quickly get used to. And if you don't get it quite right, well you just press the brake pedal! You will waste energy and lose range, but it's still safe.

It will change as battery technology changes and control systems improve. Some Teslas already automatically blend in friction brake even when the pedal is not used.

But the more it's hidden from the driver, the harder it is to drive efficiently; when the different braking methods are exposed and separated it's much easier to see that each time you have to use the brake pedal you are wasting energy. Possibly that will only improve when the car drives itself.

nib

[nib]

As I have said before, go try one. It'll not be the same as your imagination!

nib

[nib]

Also of course all this is not only relevant to EVs, the ever-expanding variety of hybrid cars have the same issue. One aspect of their increased efficiency is regen braking, in fact for some very mild hybrids it is the only real gain.

To get the benefit of regen with a hybrid it is necessary to prioritise regen over friction braking as far as possible, just like an EV, which for the greatest effect will need some means of persuading the driver to brake more gently.

My wife's petrol hybrid has the same "1-pedal" mode as my EV.

nib

[Jim Joyce]

In my experience, everyone (or surely nearly everyone) uses progressive braking, to some extent. Many probably don't know that it's called that and likely aren't aware that they're even doing it, but to do otherwise would mean there'd be a lot of head-snapping as cars approach red lights, stop signs, etc. Progressive braking is even more important when riding a motorcycle, where the biggest reason becomes safety rather than comfort. The introduction of ABS changes things a bit, too.

I remember using the handbrake on my VW Beetle in 1980. I lived in a small German village located at the bottom of a very long, straight, hill. During the winter when the road was covered in packed snow, I'd pull the handbrake to lock up the rear wheels, then I'd slide all the way down the hill, challenging myself to keep the car from swapping end for end. The rear-mounted engine really wanted to be up front. Fun times. I also remember using the handbrake in the mid-80's when I had a 4WD pick-up with a 5-spd manual. I needed to hop out of the vehicle to lock the front hubs and I didn't want to shut off the engine. Those are the only times I remember using the handbrake. If someone gets blinded by illuminated brake lights, they probably shouldn't be driving at night.

[Max Demian]

I used "cadence braking" on wet roads long before I knew it had a name. (Brake until you skid a bit, release, steer and do it again.) It seemed so obvious.

[Vir Campestris]

My wife's car has a gear suggestion indicator. It will almost always suggest the next gear when accelerating so the engine is running at the most efficient speed all the time.

I suspect if I accelerated hard in third to 40, then let go of the throttle, it would say 5th, but I've never noticed it do it.

Andy

[Commander Kinsey]

It just goes to show they realised DRLs were so f****ng stupid they had to hide them so you could see the indicator. I can see a car in broad daylight perfectly well without it being lit up. Why distract everyone? First thing I do is disconnect the stupid things.

The only thing dafter is allowing psycholists to have flashing bright headlights. I enjoy flashing my car's full beam back at them, they don't like that one bit.

I find it more precise to have two pedals, that's two complete pedal motions instead of one, with a clear divider between acceleration and braking.

The resting of the foot is a major reason I'd never use single pedal.

Anyway, braking and acceleration are two entirely different things and should never be on the same control.

[Commander Kinsey]

I wasn't contradicting it, just the way of calculating it.

The car is computerised, it should (and should be required by regulations) to make the pedal movement equal the change in speed at all speeds, just like a physical brake. People are going to be stopping abruptly by mistake. And it'll be harder to control the vehicle at lower speeds in towns, exactly the place you want more precise control.

No, the main thing is to be able to drive the car smoothly. You can look at logs on the dash after the journey if you have OCD. Otherwise, just brake gently. I don't watch the mpg indicator on my petrol car. I thrash it, or if I wanted to save petrol for some weird reason, I'd just drive slower and smoothly.