Regen Braking for e-bikes ?

[AHicks]

If this is about regen's ability to put power back into a battery, I'll admit to anyone, any time, I'm not a fan. I would not be interested in regen for that reason only.

If this is about regen's ability to brake. That IS an attribute, and anybody saying otherwise, including dealers or a manf's, is supplying inaccurate or incomplete info. It's no different than saying engine braking on a vehicle isn't practical (see how far you get with that concept). The regen question may be better handled by asking about the bike rider's need for regen. Whether or not they can use it. This is no different than asking qualifying questions about the hundred other things that should be known prior to recommending a bike - unless you're simply trying to sell a bike out of inventory.

I don't blame a flat lander for considering regen frivolous (in it's present form) . Regen at this point is about long hills, the kind that can have you running 35mph if unchecked. Until something like the GMAC with it's MUCH more effective regen braking, has been out for a while anyway. That's going to be a game changer, even for a flat lander.

 

[Trail Cruiser]

Direct drives are associated with regen braking and then PRICE. It is partially true, Stromer is a premium brand thus it also has a premium price tag. The other factor is the use of more rare earth magnets (adds to the raw cost) and also is not environmentally attractive since rare earth magnet materials are mined. With more magnets also results to increased weight (but not much).

However, that negative association are all gone with the GMAC since it does not need excess magnets and GMAC is not a proprietary ebike motor. And it has stronger regen stopping power.

 

[AHicks]

A half mile or less of down hill run is plenty of time to build up a head of steam that will be dangerous or unnerving if left unchecked.

And by design, regen does turn a DD hub motor into a regen brake!

Last, the amount of electricity consumed by a DD while coasting is small enough to be considered inconsequential. The watt meter drops to 0, with no noticeable slowing of the bike. In theory, the clutched gear drive consumes less, agreed, but from a practical standpoint, this is a non event.

 

[Ken M]

Yeah I replace my brake pads about the same frequency, that's why I bought them in bulk from AliExpress.
https://www.aliexpress.com/item/329...chweb0_0,searchweb201602_2,searchweb201603_52

Also if primary benefit of regen is to conserve brake pads, I don't think it's worth the added cost.
In addition, regen can conserve rear brake only, which has a lot less effect anyways.

It is my understanding that regen on DD hubs and clutch-less gear hubs like the GMAC having regen function added to a controller is a few $s. Maybe someone that designs controllers can actually chime in on this because I believe a lot of the negativity about regen is being put out by advocates of mid drives that can't do it.

Without a doubt that when going down a long hill when you don't want to go too fast not having to ride your brakes all the way down is a big deal - both for safety and for reduced brake wear. Let's get real riders!! The 5-10% recovery of energy isn't the primary benefit of regen but it's not insignificant either.

 

[Ken M]

Okay I ride motorcycles, obviously I do downshift for really long downhill.

The reason why some people say engine braking is better is because so that you don't cause heat fade, which happened frequently with drum brakes back in 1970s or 80s.

However, I have never felt like engine brake was needed on my ebike. And yes I do go down lengthy downhill all the time.

I can just lightly hold the brakes and coast slow if I need to, adding engine brake? Well no thanks, especially for added price and weight.

Again.... adding regen to a controller adds only a few $s. I'm sure less the cost of 1 set of brake pads and the service cost/time to install them. Are mid-drive manufacturers paying you to make false claims about the benefits of regen??? Be objective on EBR so people can make informed decisions!!!

 

[tomjasz]

I believe a lot of the negativity about regen is being put out by advocates of mid drives that can't do it.

Only those that remain clueless and use predatory sales techniques. I support mid drives but don't ever push them on people. I'm just wrapping up a gratis project for a young couple converting their kid hauler. ZERO profit, just couldn't sell them something they don't need. It was about a 4-hour project including finding replacement parts from Italy. Overall I find mids ARE oversold. One size never fits all.

added to a controller is a few $s.

Only the cheapest China controllers lack regen. Anyone adding more than a couple of dollars is also predatory.

 

[Ken M]

There is no difference between a DD hub that is on a bike with regen and one without - the capability is in the controller or not. Geared hub motor manufacturers decide for the most part that the ability to free wheel was more important than regen so the bikes were easy to ride if battery power was ever lost (riding a DD hub without a battery is like riding up a slight hill constantly). Grin added a cool feature on the Phaserunner that automatically drops the assist power to barely overcome the cogging of the motor when the battery gets to a level that I believe is user definable. The feel that with the clutch-less regen capability this mode can be used for a very long range before the battery ever goes entirely dead and then you are left with the cogging of a typical DD hub.

DD hubs are heavy mainly because the steel backing plates to complete the magnetic poles/circuit tend to be very thick. Grin has DD hub that solves that problem too. Someone should put their All-Axle hub motor in a rear wheel on an OEM bike but that is unlikely with the business failures of BionX and GoSwiss (these companies did not market well against the mid-drives). How many riders even comprehend the advantages and disadvantages of the various motor technologies - everyone is too busy trying to keep up the Kardashians to learn anything technical. We are just a dumbing down society...that's just a fact. If you've ever tried to sell something that requires some education of the public it really resonates as a hard truth.

 

[AHicks]

Timpo, it sounds like you are starting to come around. Just keep an open mind.....

 

[Ken M]

I don't have any pictures, but since you asked the question I have approx 10 miles on direct drive (Stromer ST2).

Maybe you're right, I don't know.

Maybe Giant, Trek, Yamaha, Specialized, Shimano, Panasonic will all move towards direct drive hub motor with regen.

But my personal opinion is, I doubt it.

Bosch makes DD hub motors for mopeds with regen so they know for some applications (pretty much anything that goes faster than 15mph) is better on a hub than a mid. You have to consider the mechanical efficiency of the drive system when you compare a mid to a hub drive. Mids are great a slow speed climbing because the gear ratio of the drive system is typically helping the motor but at high speeds the gear ratio is robbing torque from a mid. DD and geared hub deliver torque directly at the rear wheel. While they may sometimes have lower peak / stall torque at high speeds they are usually putting more torque to the rear wheel and most like more efficiently than mids when mechanical losses are considered.

 

[Ken M]

yeah it's good if you have a front hub motor.
You obviously know rear hub regen is quite ineffective. And I'm pretty sure you knew I was talking about rear hub regen motor.

But what kind of bike come with front direct drive motor though?
It makes sense for hobbyists and custom made ebike builders, but from the factory? Not so much.

Also there's a lot of debate doing on about adding unsprung mass, which alter the characteristics of bike in unfavorable way.
In that sense, mid drive makes sense.

If the bike has a rear suspension then the added unsprung weight of the wheel does impact how well the wheel remains in contact with the road. This "unsprung" debate isn't really about comfort its a big factor when you ridding downhill off-road because you want rear wheel staying in contact with the ground. This is where mids excel but on the street that really has no advantage (rarely if ever is the rear wheel not in contact on a road bike).

The context of this debate is very very important because the suspension of an off-road bike is about keeping the wheels in constant traction contact (not about comfort really). On a street bike a suspension it typically about comfort but I tend to think that tire in the 2.0 - 3.0 width range have enough suspension property that suspensions any street bike that doesn't assist past 30mph (or even faster) are mostly marketing for the masses (to get them to buy something that will just add upfront and service costs to the purchase.

So long as there are people that make a living in marketing, sales, and bean-counting there will be claims made that simply are not true (those that don't create, tend to fabricate to give the sense they are contributing to design). I think we all know marketing isn't about telling the unbridled truth.

 

[Ken M]

Okay sorry I didn't specify.

What I mean by "added weight" was that when I was shopping for ebikes, the geared hub motors had less weight than gearless direct drive motor, which inevitably adds weight.
Added cost, well if you look at Stromer Syno Drive, BionX, etc.. gearless hub drive aren't cheap.

Look at Bafang motor for example, they're much lighter, smaller (aesthetically pleasant) and cheaper.

DD Hub motors are actually the most economical to produce. Those brands you mentioned just make bigger margins but those are bikes intended for higher speeds where DD hub motors shine.

It's all about application. If someone just wants to leisure ride around their neighborhood at 10 mph max get a mid and you'll be very happy. If you want to do some commuting with a purpose (ie replacing your car with an ebike) you should really give both DD motors a spin and compare to the geared hubs as well which will have a bit better low speed performance but maybe not as good at the higher speeds in the 30mph range.

 

[tomjasz]

hose brands you mentioned just make bigger margins but those are bikes intended for higher speeds where DD hub motors shine.

This!

 

[tomjasz]

All this discussion about regen, did anyone see the post Ravi made about regen in another part of this forum? Tons of information there.

Hard to keep up with everyone's input. Links help others if you know where the thread is.

Thanks for the tip!! https://electricbikereview.com/forums/threads/regeneration-on-e-bike-motors.29172/

 

[Pragmatic]

Deleted Member 4210 Well darn!! Pragmatically, whether stopping/slowing in a truck or on a bike, I just hate the inefficiency of turning kinetic energy into waste heat (hot pads and hot rotors).

But as mentioned, the weight- transfer-driven dynamics drives the greater braking of the front wheel/hub, that makes rear-hub motor, or mid-powered (still rear wheel via chain) makes regen inconsequential/impractical. Again, darn! ...Ride On!!!

 

[AHicks]

Pragmatic, the amount of regen available with most systems will not be a weight transfer event. For weight transfer to be anything of any consequence, you would need something like the GMAC drive, and some very heavy duty circuitry from the motor to the battery cells to handle that kind of current. With today's bikes, that kind of regen is going to smoke most systems not designed to handle very large amounts of power.....

 

[Pragmatic]

Pragmatic, the amount of regen available with most systems will not be a weight transfer event. For weight transfer to be anything of any consequence, you would need something like the GMAC drive, and some very heavy duty circuitry from the motor to the battery cells to handle that kind of current. With today's bikes, that kind of regen is going to smoke most systems not designed to handle very large amounts of power.....

Roger.

 

[BobG]

My BionX powered Elby has regen and I don't remember ever turning it on. Nice feature if you only ride downhill.

I've enjoyed the regen feature of my BionX D500 retrofit, now close to three years old. Yes the "regen" is minimal. That said, I have one route from my house to an adjacent town that is 440' up and 1075' down where the regen feature will restore most of the power used for the climb.

If I ride directly to my town it is 480' down in 2 miles. If I leave home with a fully charged battery there will be no regen braking because the system is designed to not overcharge the battery. When the battery has a slight discharge the braking feature will kick in. When the battery is down to half the braking power is quite pronounced at level 4 regen.

I don't use the brake lever switch. One less cable to clutter the bars and the reed switch can be fussy to keep properly spaced from the magnet. I just adjust regen/assist levels manually with the G2 console. With a little practice you'll do it as fast as a teenager sending a text! For example if I want to return to level 2 assist from level 4 regen I just make six quick taps with my thumb on the + button without even looking.