Regenerative braking on an e-bike.

Electrically assisted bikes, trikes, etc.
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Cugel
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Re: Regenerative braking on an e-bike.

Postby Cugel » 2 Jun 2019, 9:56am

kwackers wrote:The energy you'd get back from a bicycle even in a hilly area might be enough to get you up your drive after several tens of miles of riding.

In start stop traffic heavy cars benefit fairly well from it, but unless you're the sort of person that is always dabbing at your bike brakes then you'll get nothing and if you are that person then learn to read ahead and use brakes only as a last resort - saving the energy in the first place is far better than recouping it inefficiently later.


Can you supply the maths to support that "up your drive" opinion? :-)

There are many back roads in Wales that are very steep, curvy, gravely and cow or tractor-mucked. Many cyclists would prefer to do more than merely dab at their brakes down such stuff, especially 5-7kms worth in one swoop.

As soon as you do have to (or choose to) use your friction brakes quite vigorously and over extended periods, you're wasting a lot of energy as heat. I suppose we could try going down a twisty-turny back road of 15% at 56mph, to use the momentum to get up the other side but I feel this is a procedure likely to end in tears.

Perhaps I am not macho enough? I know the ladywife isn't. Quite the opposite, the little darlin'!

Cugel

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Mick F
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Re: Regenerative braking on an e-bike.

Postby Mick F » 2 Jun 2019, 10:14am

With our hybrid Yaris, we can get home having come down long hills, with a full battery.
One full battery with the system warm, will allow the car to go up to 40mph - providing you do it gently - for a couple of miles on the flat without the engine kicking in. Also, we can get up our drive without the engine too. 100yds of 1in4 tarmac.


Separate subject to bikes of course, but reversing is always done on electric as there's no gearbox to put the engine into reverse.
Mick F. Cornwall

Brucey
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Re: Regenerative braking on an e-bike.

Postby Brucey » 2 Jun 2019, 10:50am

I think in Cugel's terrain with 1000m of climbing in several short bursts, there is something to be gained. And indeed there oughtn't be an enormous cost penalty in implementing such systems.

It occurs to me that in the biggest euro e-bike markets (I'm thinking of Northern Germany and The Netherlands) regen braking wouldn't be a big selling point so hasn't been pushed. In most UK uses any gain might be slight, but in some cases it would be worth having for sure.

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kwackers
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Re: Regenerative braking on an e-bike.

Postby kwackers » 2 Jun 2019, 10:57am

Cugel wrote:Can you supply the maths to support that "up your drive" opinion? :-)

There are many back roads in Wales that are very steep, curvy, gravely and cow or tractor-mucked. Many cyclists would prefer to do more than merely dab at their brakes down such stuff, especially 5-7kms worth in one swoop.

As soon as you do have to (or choose to) use your friction brakes quite vigorously and over extended periods, you're wasting a lot of energy as heat. I suppose we could try going down a twisty-turny back road of 15% at 56mph, to use the momentum to get up the other side but I feel this is a procedure likely to end in tears.

Perhaps I am not macho enough? I know the ladywife isn't. Quite the opposite, the little darlin'!

Cugel

It's not a difficult thing to do. Why not try it and see? I'd be interested in knowing how you get on.
IMO hills or not most of the energy lost by bicycles is wind resistance and hills are significantly lower - and at 56mph wind resistance is pretty immense unless you're lying prone...

IIRC your bike is mid drive? Buy a low powered hub for one of the wheels, a wind powered charger type circuit from eBay would probably be a good starting point for a controller and hook up some kind of switch to the brakes (or use the one that presumably already exists).
Ideally dump the back brake altogether and make it completely electronic, rear hub, brake lever with some kind of position sensor - although it'll feel a bit 'wooden'.

It's an interesting project, shame I don't feel it to be worth the effort. ;)

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Re: Regenerative braking on an e-bike.

Postby brynpoeth » 3 Jun 2019, 7:30pm

Interrogated a lady e-biker, the machine weighed 25 kg plus, she could never heave it up the steps, how much does Mrs Cugels bike weigh?
Instead of adding a motor, maybe upgrading to a simple light robust bike might be effective, Cugel could downgrade to a cheap heavy bike to slow him going uphill to level the playing field
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Re: Regenerative braking on an e-bike.

Postby scottg » 5 Jun 2019, 5:41pm

Cugel wrote:[snip]

As I mentioned, there may be cost and complexity issues for an e-bike of making them to provide regenerative braking as sophisticated as that of an e-car. There may be other reasons too, such as a high weight penalty for all the necessary gubbins.....? No one seems to have yet made such a sophisticated regenerative system for an e-bike. But is anyone trying, I wonder?
Cugel


Bionix have 4 levels of regen, in practice is feels like engine braking using a manual transmission.
The highest level, 4 feels like descending a hill in 2nd gear in car, you pretty much don't use the brakes,
till last few yards. Unlike the car there is no gear noise, even a 15% hill can slowly be rolled down no brakes
needed to the end. Very nice on wet roads.
You toggle the regen levels using the same control you use for assist. There is also a sensor
wired to the brake lever, that triggers the lowest regen level.
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Re: Regenerative braking on an e-bike.

Postby kwackers » 5 Jun 2019, 6:28pm

scottg wrote:Bionix have 4 levels of regen, in practice is feels like engine braking using a manual transmission.
The highest level, 4 feels like descending a hill in 2nd gear in car, you pretty much don't use the brakes,
till last few yards. Unlike the car there is no gear noise, even a 15% hill can slowly be rolled down no brakes
needed to the end. Very nice on wet roads.
You toggle the regen levels using the same control you use for assist. There is also a sensor
wired to the brake lever, that triggers the lowest regen level.

Are there any figures for its effectiveness around?

It's a good way to replace a coaster type brake though and imo reducing wear on brake parts is by far it's biggest USP.

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Cugel
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Re: Regenerative braking on an e-bike.

Postby Cugel » 5 Jun 2019, 7:13pm

brynpoeth wrote:Interrogated a lady e-biker, the machine weighed 25 kg plus, she could never heave it up the steps, how much does Mrs Cugels bike weigh?
Instead of adding a motor, maybe upgrading to a simple light robust bike might be effective, Cugel could downgrade to a cheap heavy bike to slow him going uphill to level the playing field


The ladywife's bike weighs just under 15Kg with all the bits on, including not just the motor/battery/BB gearbox but also the mudguards, bottle cages, bottle & tool bottle and the pump. It can be ridden sans motor & battery which drops out of the frame with a push of a button. This loses just over 4k so the bike becomes as light as a typical steel tourer - although it's configured as a CF framed endurance road bike.

Perhaps you haven't cycled the hills of West Wales? For an ex-racing fellow they are do-able ..... although I do, these days, need at least a 1:1 bottom gear, preferably lower on the worst ones. I have an FTP of about 230 watts and can probably hold 260 for a minute or three for the short & sharps. The ladywife probably generates an FTP of about 130 watts, not being an experienced cyclist (yet) so would be walking up a lot of those hills, even with a 7kg bike. A low enough gear would be so low to twiddle, she'd likely fall off sideways!

She weighs 8st 8llbs to my 13st 1llb (according to the scales).

In practice, she goes up the steepest long climbs in the middle power setting, pedalling as hard as she can to get the motor to give the maximum help for that setting. She drops me (trying my utmost) at a differential of 0.5 - 1mph. That means both of us get proper exercise, with plenty of aerobic threshold stuff. Such exercise is part of our intent, since not using it will only lose it. We old gimmers (well, me) have to keep at it or wither!

****
I feel you don't really understand electric bikes, in all their variety, nor the nature of riding a-one such as that of the ladywife. It still takes a lot of effort, as the BB gearbox strain gauges won't let the motor work hard unless they feel the pedaller also working hard. Perhaps you need the experience of riding such a bike before emitting opinions, suggestions and other ponderings? :-)

The Focus Paralane2 and similar road bike-style e-bikes are a pleasure to ride in the usual fashion of road bike riding. One clips along quite fast, enjoying the high heart rate, technical road management and all the usual pleasures. Why, man, we even sprint for the village signs! And up the hills, naturally.

Cugel

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Cugel
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Re: Regenerative braking on an e-bike.

Postby Cugel » 5 Jun 2019, 7:33pm

scottg wrote:
Cugel wrote:[snip]

As I mentioned, there may be cost and complexity issues for an e-bike of making them to provide regenerative braking as sophisticated as that of an e-car. There may be other reasons too, such as a high weight penalty for all the necessary gubbins.....? No one seems to have yet made such a sophisticated regenerative system for an e-bike. But is anyone trying, I wonder?
Cugel


Bionix have 4 levels of regen, in practice is feels like engine braking using a manual transmission.
The highest level, 4 feels like descending a hill in 2nd gear in car, you pretty much don't use the brakes,
till last few yards. Unlike the car there is no gear noise, even a 15% hill can slowly be rolled down no brakes
needed to the end. Very nice on wet roads.
You toggle the regen levels using the same control you use for assist. There is also a sensor
wired to the brake lever, that triggers the lowest regen level.


That's very interesting. I looked up the details and the Bionix seems to have he advantage of the brake lever applying the regen braking but a button setting how much of 4 levels. As a brake it seems a good design in that you hardly have to pull the brake lever and you don't wear out any parts such as pads, discs or rims - unless you want a lot more braking, in which case a harder application of the brake lever applies the traditional brakes.

The motor system itself is a bit heavy (about 9Kg in all, as far as I can make out) but it's surely possible to design and make a smaller/lighter version with the same power, as the relevant technologies improve a bit.

****
But it does rely on the presence of a direct drive gearless hub motor. A lot of e-bikes have the motor in the BB, In addition, there can only be regen braking on one wheel - although I suppose you could have two hub motors ........

Cugel

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Re: Regenerative braking on an e-bike.

Postby Vorpal » 5 Jun 2019, 8:07pm

This article is a few years old, now, but discusses regenerative braking on e-bikes...
https://www.electricbike.com/regenerative-brakes/
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Re: Regenerative braking on an e-bike.

Postby scottg » 5 Jun 2019, 8:12pm

Cugel wrote:That's very interesting. I looked up the details and the Bionix seems to have he advantage of the brake lever applying the regen braking but a button setting how much of 4 levels.[snip]
Cugel


The brake lever triggers regen level 1 only, it is an on/off control, not proportional.
The assist control, 4 steps of assist to 4 steps of regen is separate.
For instance on a long shallow down hill you can set regen to 1
and still pedal, the brakes are not engaged, you just feel some extra
resistance, turning the downgrade to a flat, as it were.
For a steep hill you toggle to regen 3 and near the bottom go to 4
which will nearly stop the bike on the flats.

Bionix is owned by Elby now. owners manual
http://www.elbybike.com/wp-content/uplo ... NGLISH.pdf
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Re: Regenerative braking on an e-bike.

Postby Brucey » 6 Jun 2019, 12:06pm

Cugel wrote: …...In practice, she goes up the steepest long climbs in the middle power setting, pedalling as hard as she can to get the motor to give the maximum help for that setting. She drops me (trying my utmost) at a differential of 0.5 - 1mph. That means both of us get proper exercise, with plenty of aerobic threshold stuff. Such exercise is part of our intent, since not using it will only lose it. We old gimmers (well, me) have to keep at it or wither!....


in your case it sounds like a good arrangement. In the past such disparate abilities could only be accomodated by sharing out a camping load very unevenly or by riding a tandem.

Tandem riding can be wonderful when it goes well, but if/when it doesn't, the experience has been likened to a special circle in Hell itself.

cheers
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