Regenerative braking?

Marc Draco

Pedelecer
Aug 5, 2018
31
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58
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.

We may be a little early yet (weight is clearly an issue) but I wonder how close we are to "hub" generation. The alternative hub for the hub-driven machines and both (wow!) for the crank driven.

I'm raising this now just in case some patent troll is trying to patent it (ruining it for the rest of us) because this classifies as something called "Prior art".

Clearly existing dynamos are no use - they're the wrong voltage, nowhere near efficient enough and would be running all the time which is a bit pointless. Seems that what we need (unless this is extant) is a highly efficient hub dynamo(s) [alternators are more efficient but assume I mean the same] that comes on as we engage the brakes. I thought about freewheel but that doesn't really help...
 

Marc Draco

Pedelecer
Aug 5, 2018
31
13
58
I love how they quote the output for the sort of sunlight you might get at midday on a cloudless day in summer at the equator...

Not a lot of use for Blighty! :)
 

Gubbins

Esteemed Pedelecer
For me.. on my road bike I only use the brakes a small amount so can't see any benefit, but on my jaunts over the moors on my mtb where I drop many hundreds of feet at high speed there is potential, but at speeds in excess of 40mph approaching a 90 degree corner any system would have to be robust, predictable and work on both wheels.
 
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Reactions: Marc Draco

Gubbins

Esteemed Pedelecer
I love how they quote the output for the sort of sunlight you might get at midday on a cloudless day in summer at the equator...

Not a lot of use for Blighty! :)
Oh I don't know! What with Brexit, global warming and all the cows going to market early, times may be a changing.
 

Marc Draco

Pedelecer
Aug 5, 2018
31
13
58
For me.. on my road bike I only use the brakes a small amount so can't see any benefit, but on my jaunts over the moors on my mtb where I drop many hundreds of feet at high speed there is potential, but at speeds in excess of 40mph approaching a 90 degree corner any system would have to be robust, predictable and work on both wheels.
In fact that sort of performance calls for lightweight anti-lock brakes.

Presumably someone must have done that by now for the higher-end stuff.
 

Marc Draco

Pedelecer
Aug 5, 2018
31
13
58
ABS is now on the table but it's BIG.
Big? As in heavy?

My last patent application was a decade ago (not cycling related) and we already had fairly good systems on cars then. Existing (rotational) speed sensors are almost there and already built into these motors.

Looks like the issue would be with hydraulics inline to the servo, would it not?
 

Wicky

Esteemed Pedelecer
Feb 12, 2014
2,823
4,008
Colchester, Essex
www.jhepburn.co.uk
My KTM eRace Panasonic hub pedelec (now discontinued) has generative braking & generative pedalling - all I can say its as useful for day-to-day use as the male nipple.

Unless you are going up and down and esp down long hills for miles on end i.e Alps, it doesn't bring any significant range improvement, but can save brake pad/disk wear.

 

Marc Draco

Pedelecer
Aug 5, 2018
31
13
58
This is one of those things you see and then go "It's HOW MUCH?!"

Definitely something for when the cost comes down.
 

Marc Draco

Pedelecer
Aug 5, 2018
31
13
58
My KTM eRace Panasonic hub pedelec (now discontinued) has generative braking & generative pedalling - all I can say its as useful everday as the male nipple.
Something in need of development then before it's useful for the rest of us!

(and "as useful everyday as the male nipple... OH MY SIDES!)
 

flecc

Member
Oct 25, 2006
48,539
26,246
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.

We may be a little early yet (weight is clearly an issue) but I wonder how close we are to "hub" generation. The alternative hub for the hub-driven machines and both (wow!) for the crank driven.
Quite the opposite Marc, all been done many years ago on various makes and eventually abandoned by most. So I have to waste your time by telling you it doesn't work, at least not well enough to be of enough regenerating value to offset the additional drag of an always engaged motor.

The reasons are the limited weight and speeds involved. There is the benefit of downhill braking of course and some might value that enough.

BionX have always had switchable power and regen levels on their DD rear hub motor, four levels of each so the regen usable for stepped braking force as well. However, they have been very out of favour for some while due to a lot of reliability problems in more recent production and high prices.

Giant tried regen on their Twist models from 2008 for a couple of years. The motor was a Sanyo based on the American Berkestrand Motorised wheel design that they bought, and it had been designed for regen from the outset. The Twist failed in the market though and got very poor reviews. A to B found the amount of regen was almost undetectable and remarked of the performance, "one could die of boredom".

So the Twist had the regen removed and was remarketed as the Express, much better for it.

So for me regen on bikes is a dead duck, though I'm a fan in the right applications such as on my 2018 Nissan Leaf. One and a half tonnes at anything over 30 mph really does regenerate well and in Eco mode B setting has very effective braking too.
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anotherkiwi

Esteemed Pedelecer
Jan 26, 2015
7,845
5,782
The European Union
It works in the mountains, it is a waste of time anywhere else. Stromer use a rear direct drive hub motor for a reason, they are Swiss...
 

Gubbins

Esteemed Pedelecer
Quite the opposite Marc, all been done many years ago on various makes and eventually abandoned by most. So I have to waste your time by telling you it doesn't work, at least not well enough to be of enough regenerating value to offset the additional drag of an always engaged motor.

The reasons are the limited weight and speeds involved. There is the benefit of downhill braking of course and some might value that enough.

BionX have always had switchable power and regen levels on their DD rear hub motor, four levels of each so the regen usable for stepped braking force as well. However, they have been very out of favour for some while due to a lot of reliability problems in more recent production and high prices.

Giant tried regen on their Twist models from 2008 for a couple of years. The motor was a Sanyo based on the American Berkestrand Motorised wheel design that they bought, and it had been designed for regen from the outset. The Twist failed in the market though and got very poor reviews. A to B found the amount of regen was almost undetectable and remarked of the performance, "one could die of boredom".

So the Twist had the regen removed and was remarketed as the Express, much better for it.

So for me regen on bikes is a dead duck, though I'm a fan in the right applications such as on my 2018 Nissan Leaf. One and a half tonnes at anything over 30 mph really does regenerate well and in Eco mode B setting has very effective braking too.
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Just digressing slightly here.. I have been reading about leaf buyers being unhappy about the difference in published and actual consumption, miles per charge or however you would describe it.
As an owner what's your view?
 

flecc

Member
Oct 25, 2006
48,539
26,246
Just digressing slightly here.. I have been reading about leaf buyers being unhappy about the difference in published and actual consumption, miles per charge or however you would describe it.
As an owner what's your view?
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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