Regenerative braking?

Gubbins

Esteemed Pedelecer
Esay answer Gubbins. Like all car makers they used the old way of measuring range (mpg in most cars) and it resulted in hopelessly optimistic range, just like the mpg. Under that old standard my Leaf should have up to 230 miles range, no chance.

However the new standard now being used by all makers is WLTP (Worldwide Harmonised Light Vehicle Test Procedure) and that is much better.

For my car WLTP forecasts 168 miles.

I haven't had the car long but I've given it two range tests. On the first I was driving it as hard as I could, but that limited by south east traffic conditions. However I managed some 80 mph overtakes and a flat out climb from the low level of the Weald to the top of the North Downs during the driving. I covered 104 miles and there was 30% left in the battery. I discounted that 30% by the amount that the 104 miles from 70% indicated and the end total was a range of 152 miles. Bear in mind I didn't use the Eco setting at any time and wasn't trying for regeneration, only for performance, so that 152 miles compared favourably with the 168 indicated for normal driving.

The second range test was entirely done with normal driving but again never using Eco. On that, having gained confidence with what it could do, I ran the battery very low in the final stages close to home. The "charge now" warning came up witn 11% left and 142.4 miles covered, but I ignored that and carried on down to 3% and 155.2 miles covered. The 3% represents 4.8 miles of 160 and I used that to go the last bit home including climbing my 14% hill to the garage. So I'd covered exactly 160 miles with a tiny bit left in the battery.

I think that validates WLTP's 168 mile claim, and I could easily exceed that by using Eco and it's higher regeneration.

I've also been investigating the linearity of the new Leaf's "Mileage left" indications. When first fully charged from the Pod Point home charger it can read anything from 170 to 174 miles. However, for the first 30 or so miles the indicated range reduces at anything up to double the actual miles covered, so the non-linearity is all at the top end when there's plenty left, very sensible.

At the bottom end when there's not much left it's very accurate with my driving, delivering exactly what's promised.
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Thanks fof that!
It's something in the pipeline for me so it's handy to hear a real evaluation. Possibly next year with the leaf being the obvious choice but I think it's s bit big for my garage..
 

Wander

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Aug 8, 2013
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... because it's already being used on cars.
It doesn't really work in cars though does it. The stupidly small amount of power regenned in braking before a roundabout is used up before you are half way around said roundabout.

Let's be honest there is no practical effect at all, it's just part of the marketing.
 

KirstinS

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Apr 5, 2011
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Forgive me, I don't follow the op

Is this an idea for regen that somehow doesn't involve a dd hub ?

If so it may have some legs (though personally very dubious )

If not then others have tried and failed. Or not failed exactly , I mean it does works . But the upside in teeny extra power recouped is massively overcome by the, efficacy, repairability, complexity and cost to be anything other than a marketing thing. As others have said more eloquently than me !


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flecc

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Oct 25, 2006
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Thanks fof that!
It's something in the pipeline for me so it's handy to hear a real evaluation. Possibly next year with the leaf being the obvious choice but I think it's s bit big for my garage..
That garage size was my worry, but it fits neatly and the sonars and cameras display on the screen allows absolute inch perfect precision in placing it just inside with space at the front to plug in.
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flecc

Member
Oct 25, 2006
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It doesn't really work in cars though does it. The stupidly small amount of power regenned in braking before a roundabout is used up before you are half way around said roundabout.

Let's be honest there is no practical effect at all, it's just part of the marketing.
It's not quite as bad as that. I've yet to evaluate it with the same care I used in assessing the range, but it's already evident there is a usable difference.

The best indicator of regen in cars is probably the Toyota Prius. Driven moderately it gives diesel mpg with a petrol engine, something an equivalent petrol only car cannot do.

Even driven hard to kill the range by the Top Gear goons it gave 37 mpg, something no petrol only car of that size will do when driven hard. My slightly smaller last petrol car only gave 27 mpg driven very hard when new.
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Gubbins

Esteemed Pedelecer
That garage size was my worry, but it fits neatly and the sonars and cameras display on the screen allows absolute inch perfect precision in placing it just inside with space at the front to plug in.
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In my smallish new build type garage I have
2 E-bikes.
E-lawnmower.
E-cultivator, E-strimmer and E-Leaf vac.
E-charging station.
Petrol rotovator
CH boiler and associated pipework.
Double Tool cabinet.
Bike stand and other general cycling parifinalia.
Wheelchair.

Audi A1 which has 100mm sideways to spare and about 300mm front to back.
It's a tricky parking menouver which is not to be attempted when pissed and I am sure the leaf is considerably larger than the Audi.
 
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flecc

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In my smallish new build type garage I have
2 E-bikes.
E-lawnmower.
E-cultivator, E-strimmer and E-Leaf vac.
E-charging station.
Petrol rotovator
CH boiler and associated pipework.
Double Tool cabinet.
Bike stand and other general cycling parifinalia.
Wheelchair.

Audi A1 which has 100mm sideways to spare and about 300mm front to back.
It's a tricky parking menouver which is not to be attempted when pissed and I am sure the leaf is considerably larger than the Audi.
I had a lot of stuff in my garage with the Suzuki SX4 SZ5 which is 13 inches shorter than the new Leaf but the same width.

The answer for me was to be ruthless in loading up for a visit to the council tip!

But it seems you need a garden shed or tools cupboard.
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Gubbins

Esteemed Pedelecer
It's not quite as bad as that. I've yet to evaluate it with the same care I used in assessing the range, but it's already evident there is a usable difference.

The best indicator of regen in cars is probably the Toyota Prius. Driven moderately it gives diesel mpg with a petrol engine, something an equivalent petrol only car cannot do.

Even driven hard to kill the range by the Top Gear goons it gave 37 mpg, something no petrol only car of that size will do when driven hard. My slightly smaller last petrol car only gave 27 mpg driven very hard when new.
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I had my last car 3.5 years and never reset the computer from new so 17000 miles or so it did 43mpg, and that's with the allegedly more efficient multi cylinder technology. Current car is exact same model but without the cylinder on demand technology which has been replaced with lift and coast and so far it is averaging 47mpg yet today on a run around the sales it did 63mpg.
As with most cars its not possible to drive it hard..
 

Gubbins

Esteemed Pedelecer
Wanna bet? :D

You've never seen me really drive hard.
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What I was meaning was that modern cars just go so fast.. To drive mine hard ( 1.4 Turbo DSG Double Clutch 7 Speed box) in Sport mode it red lines in every gear whilst its floored and 70 on the bypass comes oh so quickly, and you cant keep this up for long cos you run out of straight road. If I were to do that on twisty roads, if you cant keep your foot down hard it starts short shifting.. still accelerating hard enough to lose traction but not enough to stress things. I have had a few goes going fastish in manual which doesn't really do it for me.. The flappy paddles I can manage OK but not the sequential gear lever.. it just feels so wrong and I want to revert to the normal way, which of course I cant.
All I am saying is, someone could drive far too fast and in a reckless and dangerous manner but not necessarily stress a modern car especially with traffic volumes as they are.
 
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flecc

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What I was meaning was that modern cars just go so fast.. To drive mine hard ( 1.4 Turbo DSG Double Clutch 7 Speed box) in Sport mode it red lines in every gear whilst its floored and 70 on the bypass comes oh so quickly, and you cant keep this up for long cos you run out of straight road. If I were to do that on twisty roads, if you cant keep your foot down hard it starts short shifting.. still accelerating hard enough to lose traction but not enough to stress things. I have had a few goes going fastish in manual which doesn't really do it for me.. The flappy paddles I can manage OK but not the sequential gear lever.. it just feels so wrong and I want to revert to the normal way, which of course I cant.
All I am saying is, someone could drive far too fast and in a reckless and dangerous manner but not necessarily stress a modern car especially with traffic volumes as they are.
Yes, some modern cars do indeed make it difficult to stress them. It's easiest with the smaller conventional ones.

Driving unsociable hours as I've done can do the trick though. Every run to my brother's in Dorset for a number of years was done in just under two hours for the 140 miles. Less than half is motorway and much of it narrow lanes at the other end.

In normal hours impossible, but setting off from mine at 4am or setting off from the other end at 2am, no bother. You'd perhaps be surprised how many are cruising at 100 mph or much more at those times and there's never any evidence of police.

The smallest car doing that was a 3 cylinder 1.2 Skoda Fabia, so you can guess how hard that was working, right on the limit nearly all the time!
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Gubbins

Esteemed Pedelecer
Yes, some modern cars do indeed make it difficult to stress them. It's easiest with the smaller conventional ones.

Driving unsociable hours as I've done can do the trick though. Every run to my brother's in Dorset for a number of years was done in just under two hours for the 140 miles. Less than half is motorway and much of it narrow lanes at the other end.

In normal hours impossible, but setting off from mine at 4am or setting off from the other end at 2am, no bother. You'd perhaps be surprised how many are cruising at 100 mph or much more at those times and there's never any evidence of police.

The smallest car doing that was a 3 cylinder 1.2 Skoda Fabia, so you can guess how hard that was working, right on the limit nearly all the time!
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Point taken.
When I replaced the other Audi (the COD 150PS ) with this one I intended to buy the 3 cyl 95ps one for that reason exactly as a report I had read said it's great fun to rev it up without breaking the speed of light but the salesman talked me out of it he argued I wouldn't like the big drop in power so went for the 1.4 120ps instead.
 

Woosh

Trade Member
May 19, 2012
15,846
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Southend on Sea
wooshbikes.co.uk
Now before everyone jumps on me and starts talking voltages and currents, please be aware that this is something I'm already quite familiar with so let's not all waste time trying to explain the physics of why "this can't work" because it's already being used on cars.
it is still useful to set the general scene:
the expected gain by regenerative braking is illustrated by this equation:

Gain = motor efficiency * recuperated proportion of braking energy * proportion of braking
Typically: Gain = 0.6 * 0.8 * 0.1 = 4.8%
It is of course only possible in direct drive motors, in all other arrangements, the additional weight and cost of the KERS outweighs the possible gain.
 

flecc

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Oct 25, 2006
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Point taken.
When I replaced the other Audi (the COD 150PS ) with this one I intended to buy the 3 cyl 95ps one for that reason exactly as a report I had read said it's great fun to rev it up without breaking the speed of light but the salesman talked me out of it he argued I wouldn't like the big drop in power so went for the 1.4 120ps instead.
Another example of this was my tinny (yes, tinny, not tiny) little Chevvy Matiz with the 1 litre four. I only tried it once on the open road and it struggled above 60 mph, though if given a day or two would reach 95.

But around town it was great fun, very nippy driving it foot down, freely revving through the box. There's a lot to be said for a car only just up to the road environment it's to be used in.

The new Leaf has changed my driving already though. It's so quiet and smooth and the degree of control so precise that I'm super relaxed in its peaceful environment and happy to just go with the flow, however slow that is. It's enjoyable at any speed. I'd never have believed this could happen so completely, despite the test drives. It's definitely the best and most relaxing car to deal with very heavy traffic conditions, so perfect where I live.
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Gubbins

Esteemed Pedelecer
it is still useful to set the general scene:
the expected gain by regenerative braking is illustrated by this equation:

Gain = motor efficiency * recuperated proportion of braking energy * proportion of braking
Typically: Gain = 0.6 * 0.8 * 0.1 = 4.8%
It is of course only possible in direct drive motors, in all other arrangements, the additional weight and cost of the KERS outweighs the possible gain.
Here we go wirh numbers and equations again..
A bike and rider weighing 120kg dropping 1000ft over a mile or so must need a lot of energy to keep the speed down. Surely this energy if harnessed must make a difference. One of my rides to my daughters house of about 6 miles is all uphill to the mid point and then down the other side, and then the reverse and these downhill need a lot of braking. I agree that without big hills there is no benefit but without big hills to zap the battery we don't need it anyways.
 

Gubbins

Esteemed Pedelecer
Another example of this was my tinny (yes, tinny, not tiny) little Chevvy Matiz with the 1 litre four. I only tried it once on the open road and it struggled above 60 mph, though if given a day or two would reach 95.

But around town it was great fun, very nippy driving it foot down, freely revving through the box. There's a lot to be said for a car only just up to the road environment it's to be used in.

The new Leaf has changed my driving already though. It's so quiet and smooth and the degree of control so precise that I'm super relaxed in its peaceful environment and happy to just go with the flow, however slow that is. It's enjoyable at any speed. I'd never have believed this could happen so completely, despite the test drives. It's definitely the best and most relaxing car to deal with very heavy traffic conditions, so perfect where I live.
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Is this what's called thread hijacking?
 
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flecc

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I agree that without big hills there is no benefit but without big hills to zap the battery we don't need it anyways.
With bikes low weight yes, but not with electric cars. Even in flat areas, if any braking is done, it must be an advantage to turn that into charge current rather than brake pad heat. Not only a range advantage but also a running costs reduction.
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Gubbins

Esteemed Pedelecer
Well to stay on topic..
In the manual for my last car it said something about regenerated energy from braking was stored as an over voltage in the battery for use when required. Or sumsuch.
I could never understand how that ciuld work.
 

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