No. The problem with regen with simple DC motors for example is that as the speed reduces there is not enough voltage to drive ANY current back into the battery, even though there is still energy to be recovered.
The boost converter allows the voltage to be increased to achieve enough voltage to actually push current into the battery, at a lower current of course to result in the same power being recovered. No laws are being broken.
Think about a simple permanent magnet DC motor. To run at speed N from a supply voltage V its back emf at N must be less than V. So it cannot be used directly for regen into the supply voltage because while slowing down, speed less than N, its generated voltage cannot exceed V.
nib
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Andy Bennett
Gnattpower regen from the motor/gen gives you gnattpower breaking no matter which way you cut it.
Btw motors used in EV's tend to be multiphase synchronous motors.
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Andy Bennett
Apologies for the breaking/braking trap I just unwittingly fell in to!
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nib
Indeed they are. Or asynchronous in some cases.
I don't quite get what you are talking about. Regen in modern cars is quite powerful. Not as powerful as friction braking but if you drive carefully you can almost avoid using the friction brake. The motor in mine is 100kW and it can regen up to about 40kW and come down to walking speed without the friction brake, so you need only to touch the brake for that last small bit.
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nib
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Andy Bennett
Precisely!!
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charles
[Snip]
I had a friend who tried "engine braking" to slow his car down. The engine was going rather too fast for the lower gear he selected so he ended up with "engine braking".
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Theo
You need to use the friction brakes regularly to prevent the discs from getting rusty. Ideally you want a bit more energy than you have at 3mph, but it's a reason why there's no point trying to avoid using the friction brakes completely.
Theo
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Theo
People do that to have guaranteed use of the vehicle. If you use it to drive to work at 8am, that's when everybody else also wants to use theirs. So you'd find you can't get one when you want one.
Also, if the same vehicle was used 10x more, you'd find it fell apart 10x quicker. To avoid that you'd have to build it more robustly - more like a train than a car, with similar costs. It would also need a similar maintenance regime to make it last as long as a train - go in for servicing once a week.
(The same is why cheap DIY tools don't last when used professionally - because they're only specced to be used for a few minutes a year, not 40 hours a week. And they aren't made to be serviced)
Theo
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Andy Bennett
VW EV's use large diameter drum brakes on the rear (RWD) for this very reason. Works well.
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nib
I don't know about others, but given that regen cannot match what friction braking can do, in traffic it is sometimes hard to time your deceleration to do it all on regen when others are friction braking, so I use the brakes quite often enough!
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Bob Eager
I have recently discovered a small problem. On short journeys the actial brakes are used so little that I am getting corrosion of the discs.
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Bob Eager
My car won't apply the physical brakes if regen will do the job.
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RJH
Well, that little lot is pretty much made up. But it does get to what I think is one of the main issues - what people /think/ car sharing is all about*.
Often wondered how low range decent (Lidl/Aldi say) stack up against pro-grade hand and power tools.
On power tools I'm not certain there's a huge difference having just bought some mid-range Makita kit. The few decent hand tools I've got, especially those that cut or have moving parts, are a relative joy to use compared to cheap tat.
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alan_m
Where friends live the current availability of taxis at certain times of the day is non-existent as the few that are available in this rural area are fully book well in advance. They are booked for the school run etc. every day during term time.
I cannot see self driving cars is going to change the availability in many areas.
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alan_m
It depends a lot on your circumstances. If you are retired you probably have a different view about car use to those who may be commuting most days of the year and if time is more important than costs.
Now retired I have more of a choice when I go to the large supermarket and I can avoid using the roads at the busy times, especially school run times.
Until you use a tool with some quality you possibly don't realise how much time it saves or how much easier it is to provide a quality output.
For the one off or infrequent job a cheap tool may be more than adequate but the more expensive tool may have metal gearbox, rather than plastic, the base plates or guides may be a thicker material and don't bend when in use, better manufacturing tolerance may mean the tool doesn't vibrate or the chuck runs true. A cheap tool may/will also come with a cheap consumable and often just changing a blade can make a significant difference.
Tools in the hands of people using them every day are usually not handled with kid gloves nor are they cleaned at the end of the day. While in the hands of a DIYer a Aldi/Lidl tool may last many years I doubt that on a typical work site they would last more than a week.
I have a relatively small hedge that I cut around 3 times a year. When the previous hedge trimmer died I purchased a Lidl £25(ish) replacement. It works well but with 15 minutes of continuous use it must be rested for a while as the smell from the casing indicates that something is getting warm :( I'm sure it will last me many more years If I use it in a way that protects it from its cheap design :).
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Theo
I had to replace discs and pads because the caliper siezed through lack of use...
I now try to do an emergency stop once a week or so, just to keep everything polished.
Theo
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Jethro_uk
Nothing you say is wrong. For 2024.
However, the history of the average person being able to own their own means of transport is so short as to hardly warrant a page in "The History of the World from stone axes". And may well turn out - like smoking - to be a blip in the line of time.
We are already seeing cars getting more expensive ... add that to the whole Uber model [passim] and it's not impossible that we see syndicates buying the - f****ng expensive - autonomous cars and then running them via an Uber-type app to extract maximum value from them.
The "Everyone wants them at once" problem is easily solved with a combination of surge pricing and - shock horror - *sharing*. Which for people old enough to remember was how Uber started.
Interestingly I notice that Uber now offer a "Wait'n'save" option which offers a c.10% discount on your ride if you are willing to wait 10 minutes instead of 2.
I am always sceptical of prognostications of the future that are based on how things are today. In 2019, the golden rule was "we can't possibly do remote working". It was an accepted fact of modern life. Come 2020 and all of a sudden *everybody* (that didn't want to go bust) mysteriously discovered they could offer remote working. All the woes of the workplace we are now seeing around WFH stem from a workforce that realised they were being lied to. And another facet of "me" is when I uncover one contradictory fact, I assume it's not isolated.
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Tim Streater
When I lived in the US I volunteered for a semi-pro (as it was then) theatre group and a semi-pro (as it still is) opera company. Interesting that all the techs for these outfits (often the same bods) all used, without exception, Makita kit. This was in the 1980s.
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charles
Some 60 years ago, when embarking on DIY projects, I bought a Stanley Bridges power drill. At the same time, my BiL bought a Black and Decker. By the time, I retired mine, he'd been through 3 B&D ones. I'd probably done more work with mine, too.
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Tim Streater
While I agree that this is quite possibly what will happen, getting the masses to accept it will be interesting.
There'll just be more second-hand rattletraps on the road.
Well, they found they could offer WFH simply because that allowed there to be at least *some* productivity from all those laid-off bods, but now they want people back in the office in order to restore pre-pandemic productivity levsls.
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