Regenerative braking, is it all hype?

[Cyclezee]

Please excuse me if this topic has been discussed before.

I am trying to establish if members think regenerative braking is a virtue for electric bicycles or a complete waste of time and not worth investing extra money in.

One of the first questions I am asked by non electric powered cyclists and the public in general is "does the battery recharge itself?".

My stock answer is a bike is not an F1 racing car or Hybrid with an internal combustion engine, and the amount of energy that can be generated when braking a relative light vehicle like a bike, even on the steepest of hills, is tiny by comparison and not worth the extra cost involved. You are also going to loose momentum by braking heavily going downhill to generate power. That momentum could have carried you part way up the next hill, and you will use more battery power than you might have to climb it.

Surely the laws of physics win every time?

Please discuss......

 

[lemmy]

I doubt anyone will disagree with your analysis of the situation. Too much outlay for too little return.

 

[funkylyn]

Well, my opinion, for what its worth is.....you are exactly right in your analysis......its a complete waste of time and money.....
The G.P. who dont understand the first thing about e- bikes think mistakenly that it would be sensible, but in practice it isnt for all the reasons you state.

Lynda

 

[eclectic_bike]

Agreed, but I do like the idea of using regeneration to brake and get something back in return.

 

[Scottyf]

Depends how much regen braking actually affects the bike. If it was twice as much as a free wheel geared hub in additional friction I wouldn't mind it.

Problem comes whence battery runs out

 

[oigoi]

If you are someone like me who lives in a hilly area you would appreciate regenerative braking, as it would save a lot of wear on your brakes and the time I spend adjusting them and fitting new pads, which is a useful benefit regardless of how much energy is captured by the system.

 

[funkylyn]

If you are someone like me who lives in a hilly area you would appreciate regenerative braking, as it would save a lot of wear on your brakes and the time I spend adjusting them and fitting new pads, which is a useful benefit regardless of how much energy is captured by the system.

Yes, but the problem is there isnt enough generated to make a reasonable difference...if it worked well in reality we would all like it.....

Lynda

 

[oigoi]

Yes, but the problem is there isnt enough generated to make a reasonable difference...if it worked well in reality we would all like it.....

Lynda

Hi Lynda I think you misunderstand me, I wouldnt mind if the regenerative braking put no energy whatsoever back into the battery, the fact it would save me from buying so many new brake pads and having to adjust my brakes all the time would be a good benefit for me

 

[funkylyn]

Hi Lynda I think you misunderstand me, I wouldnt mind if the regenerative braking put no energy whatsoever back into the battery, the fact it would save me from buying so many new brake pads and having to adjust my brakes all the time would be a good benefit for me

Put it down to extreme tiredness and over excitement Oigoi......but of course, this morning after a good nights sleep.........ting !......brain now back in gear.....now I have re read what you wrote.....
understood .......and a very good point


Lynda

 

[Cyclezee]

Systems like BionX certainly give effective braking, but in this example only on the rear wheel and at considerable cost.
In comparison, hydraulic rim or disc brakes require no adjustment when fitted correctly and with good quality brands, the blocks or pads last for thousands of miles in normal use.

 

[flecc]

Although the braking can be a benefit, overall not worthwhile, and diefinitely not on internally geared hubs where the lack of a freewheel means high drag. This was what killed the Giant Twist 1 and 2 models in the market, prompting them to remove regen and fit a freewheel on the subsequent well named Freedom model.

More viable on direct drive motors like the Bionx with switched regen, where drag isn't a problem.

 

[Scottyf]

On direct drives there is no free wheel.
How much drag with regen do these motors actually create?

I've never used a direct drive but would like to know actually how much they really do drag.


I still like the geared motors though. the free wheel gives me the option of just using it as a normal bike which I love.
I ask because a couple of times the BPM clutch hasn't disengaged and it wasn't really that much of a problem to cycle with it engaged. Yes it took more effort but not that much...

 

[piotrmacheta]

I agree that there is little benefit for battery recharge but I think there is an advantage on slippy surfaces as you can arrange to have them as anti-lock brakes - I think. Would be great for smaller wheels as my 20" lock up ever so easily.

 

[oigoi]

I like the idea of and a.b.s. On a car you have a sensor that detects if the wheel is not turning an releases the brake, perhaps a similar thing could be done with hall sensors?

 

[Deleted member 4366]

I ask because a couple of times the BPM clutch hasn't disengaged and it wasn't really that much of a problem to cycle with it engaged. Yes it took more effort but not that much...

If you clutch fails to disengage, just ride off a kerb, or, if it's front wheel , just jump the front wheel as if you were going to go up a kerb. the small jolts will probably be enough to free it. My last one sticks sometimes, so that's what I do and it works every time. Thankfully, it's getting easier to disengage with more miles, so I'm hoping eventually, it'll go away completely..

 

[Scottyf]

I think it's because I ride it quite aggressively that it does it lol. Keep jumping of things to get some air. I'd like to make a more heavy duty off road bike with full suspension in the future with a direct drive but all in good time.

Does anyone have any comparisons with motor drag on direct drive vs geared?

 

[wurly]

Regeneration? thats marketing talk for no freewheel isn't it?

I've been planning my next ebike and was going with a DD hub but after speaking to someone with a 9C hub, i've changed my mind. You really wouldn't want to pedal one very far with an exhausted battery. I'm probably going for 500W BPM or MAC hub from cellman, probably the latter after hearing about the BPM clutch problems!

 

[aseb]

ok, all similar views - but no-one says they've used it? How about views from people who have it, or have used it (not just read about it, or just tried it once or twice?)

Well- I have. I can choose whether to enable it, or to disable it with my programmable controller. And even when it is enabled in the controller I have full choice of whether to use it on a hill by hill basis. Braking effect is good when using regen, with 2 levels settable on my controller- one is a sharp braking effect. I was advised that if connected to your brake lever that the best choice is to connect it to the wheel that isn't powered. Mine is set up so it only operates if the throttle is open when the rear brake lever is slightly squeezed (so no brakes being used). If there is no throttle being used then there is no braking effect. The braking effect can save a lot of wear of your brake pads.

If you are planning on using regen make sure that you have a good torque arm, and there is no free play when going from accelerating to regen- it won't take long to destroy your forks.

That said the actual regen amount isn't phenomenal where I am. There are hills all around, reasonably steep but not miles long where the regen is needed a lot.
Some regen figures taken from the 8 rides- 1.3% 1.4% 1.3% 1.7% 1.7% 1.3% 2.4% 9.8%
The last figure was higher- deliberately trying to get the regen figure up to see what I could get- I've hit that level a few times but normal use with no attempt at careful energy usage, efficiency or consciously remembering the presence of regen and deciding whether to deploy it- it is around 1.5% for me.

Is it worth it? Possibly not, but it is free, and takes no effort on my part.

But if you are going to use it make sure that torque arm is doing its' job or there could be serious consequences.

Added- I just remembered the question about drag. Direct drive clutchless motors have drag- it doesn't matter whether you use regeneration or not. As I turn my wheel by hand I can feel it as the stators move between the 15 (I think) magnets. I don't notice it when riding but there must be greater drag than other designs but it doesn't feel any worse than the brushed motor it replaced, and is better in every other respect from noise, smoothness, wider power band and efficiency standpoints.

 

[overlander]

I use it all the time on my bionx system as i have a fair amount of very long hills and they are a pain to keep your hands on the brakes. On the Trek you have 4 settings and i regulate my speed using these setting and just coast at the speed i set. But as for extra battery life i really do not think it add much. As for drag on the bionx system when its off i would say there is none, but from what i hear a direct drive should have some, will look closer tomorrow but if there is any then its small.