Yes as far as i know. Its one way they eke out the range. I generally only touch the brake pedal for the final few metres to come to a stop.
No new petrol or diesel cars by 2040
- Thread starter John D v2.0
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Yes as far as i know. Its one way they eke out the range. I generally only touch the brake pedal for the final few metres to come to a stop.
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The old Milk Floats I don't think had regenerative braking, and neither did the old fork lifts, but by 1984 CAT fork lifts had regenerative braking but not through the brake peddle, correct procedure was to put them in reverse, in real terms it did not work as instead of just stopping they would start going back wards, so not really used even if that is what the manual said to do.
In a way even the old steam engines had regenerative braking putting them in reverse while going forward pumped air into the boiler. It is only the internal combustion engine which did not have the option.
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depends if you're from a standing start or driving on the flat at 30mph, etc. Stopping from speed and getting to speed are the most energy intensive parts of a journey, hence why driving at constant 40 is more efficient than stop start.
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If I've done my sums right, assuming a 1,000kg car and assuming 100% efficiency in converting the car's kinetic energy into electrical energy, braking from 30mph to zero would produce about 89,780 Joules, aka about 25 Wh (i.e. 0.025 kWh). I've no idea how far the car could go with that amount of electrical energy!
Kind Regards, John
D
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What about nuclear powered cars then? A little nuclear reactor in everyone's boot? There's got to be some mileage in that idea.
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Assuming a spherical car in a vacuum, anywhere you like!
The mass of the car is irrelevant. If your regenerative braking is 100% efficient then surely you would be accelerating at the same rate when decreasing velocity as increasing it?
But even if you were, that would not be enough - every "ordinary" car can accelerate far more when slowing down than when speeding up.
Where are you suggesting that all the kinetic energy of the moving car (which is proportional to its mass) goes when it is brought to a halt? As I said, I was assuming that all that kinetic energy would be turned into electrical energy, although that obviously is not the case in the real world. In the absence of regenerative braking, that energy will be converted to heat.
Maybe it's because of the time of day (or 'old age') but, I'm sorry, I don't understand that.
All things being equal, the rate of deceleration does not alter the total amount of kinetic energy which needs to be converted to something else (heat in the case of a traditional vehicle) when one slows (or stops) a moving vehicle.
Kind Regards, John
AIUI, yes they do - though it's a user configurable parameter (according to some articles I've read). Again, this is from reviews I've read, not first hand experience, but when you "lift off the gas" they go into regenerative mode - to give a feel like engine braking. The first stages of pressing the brake pedal also trigger more regeneration. I've certainly read comments that if set to use more "engine braking", the feel is quite distinctive.
Well given the impressive figures* they get for urban driving, one has to assume that it has some effect on consumption. AIUI electric-mechanical conversion and the reverse isn't too bad efficiency wise - so you might save (stick finger in air) say 50%. That's 50% of your kinetic energy not going to heat the atmosphere.
However, in the case of the Toyota hybrid system (I'm not familiar with the layout of the others), the hybrid (ie battery storage) part plays only a limited effect on consumption - the bulk of the gains are due to the variable ratio "transmission" inherent in the design. Something like the Torotrak system can achieve most of the gains in fuel consumption without all the lecky bits - it just doesn't have the lecky storage ... Except that I see from their site that they now have a flywheel storage system which will deal with the "recover energy while braking, use it to start off again" bit that makes urban driving so high in consumption.
* Anyone remember the Top Gear demo where they had a BMW M3 (IIRC) following a Prius being driven flat out round their track - and the M3 used a lot less fuel than the Prius
Add that to complaints that real-world figures were massively different to the official test ones, and one can only speculate that the official tests at the time (I believe they have been changed) were easily "fudgable" by programming the system to fully deplete the batteries during the test, and thus use energy that the test didn't account for
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The Bedford CF electric van back in 1970's had the duel regenerative braking first on releasing throttle then on first part of brake peddle. That is nothing new. However hybrid is something new, there are so many types, those which use electric to give it more acceleration and are not designed to be fuel efficient are still electric hybrid, with a petrol/electric in the same way as diesel/electric trains where they can use full electric power under the power lines, but can still run where there are no power lines, having a petrol engine which simply extends the range of the car is very different to one where the petrol powers rear wheels and electric powers front wheels to give extra acceleration.
We will need a hybrid car, which is in essence a small generator to extend the battery life, but in the USA the rules say the electric car must be able to be charged from a electric point to be able to take advantage of the specials allowed for electric cars, special lanes on their highways etc. The USA Prius is not the same as ours.
The Australian bus idea is what we want, in the country they run on diesel like a normal bus, but in town they become a tram. No need for batteries so cheaper and lighter, so use less fuel, the whole idea of an electric car is flawed, what we need is public transport which means we don't need a car. A car for pleasure great, but where is all goes wrong is when we need a car to get to work, to use the car because we are late, or simply want to is one thing, to use the car because there is no alternative public transport (and not counting taxis as they are cars) is another.
We will need a hybrid car, which is in essence a small generator to extend the battery life, but in the USA the rules say the electric car must be able to be charged from a electric point to be able to take advantage of the specials allowed for electric cars, special lanes on their highways etc. The USA Prius is not the same as ours.
The Australian bus idea is what we want, in the country they run on diesel like a normal bus, but in town they become a tram. No need for batteries so cheaper and lighter, so use less fuel, the whole idea of an electric car is flawed, what we need is public transport which means we don't need a car. A car for pleasure great, but where is all goes wrong is when we need a car to get to work, to use the car because we are late, or simply want to is one thing, to use the car because there is no alternative public transport (and not counting taxis as they are cars) is another.
As you will have seen, my recent calculations (if I got them right) suggest that, for a 1000 kg car, and assuming 100% 'regeneration efficiency', braking from 30 mph to rest would regenerate about 25 Wh of electricity. Taking your guesstimate of an actual efficiency of 50%, lets say that a more realistic figure is 12.5 Wh for one episode of such braking.
That does not sound like much. However, if one considers doing the equivalent of that once per minute for an hour (far from impossible in urban or otherwise congested driving) one is talking about 750 Wh. Quoted figures for EVs seem to average at around 200 Wh/mile, so that saved energy might take one nearly 4 miles extra. Still far from enormous - but far better to use that energy than to just let it waste your money and add to global warming!
Money-wise, if one did that every day for 5 days per week, if one assumes an 80% 'charging efficiency' (I haven't a clue!), and if one charges using night-time E7 electricity, that regeneration would result in an annual saving of around £17 - again, no fortune, but still not to be sneezed at!
Another saving resulting from regenerative braking is, of course, a very marked reduction in wear of brake pads/shoes and brake disks/drums - hence reduced maintenance costs. I have no idea how to quantify this, but it might well be greater than the 'fuel saving'.
Kind Regards, John
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Back into the battery.
Yes - it is not a realistic model, but theoretically you accelerate a mass to x m/s, and then you accelerate it to 0 m/s. The mass is irrelevant.
Or maybe because it was nonsense.
In this theoretical 100% efficient closed system, there is no reason why the accelerations should be the same. If you've gone from zero to whatever in t seconds, then you could go from whatever to zero in any time you like, and be 100% efficient if you convert all of your kinetic energy to potential, instead of using some of it to make noise and heat.
So, sorry for that.
However:
We do not think it strange, or against the laws of physics, if an EV can be fast charged in less time than it can be fast discharged, i.e. used.
So I don't see why, per se, a car could not recover kinetic energy at a faster rate than it creates it.
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