6

Not asking for opinion which one is better, so please do not state without some reasons why one is better than another on eBike.

Question is: Freewheel or Regenerative braking is more efficient in Electric Bicycle?

So far I got:

Freewheel:

  • When battery go flat you can use it as a normal bicycle, while with RB it feels like riding with a flat wheel (or even worse).
  • It is lighter than hub with RB, and cheaper
  • Similar to a bike

Regenerative Braking (RB)

  • You can charge your battery up whenever you need to stop, albeit minimal.
  • It helps you brake the bikes gradually, especially on downhill section, just like how motorised vehicles work.
  • Akin to motorised vehicle
  • I wouldn't count "It helps you brake more gradually on downhills" as a tangible advantage, since unless you're on a loaded touring bike or tandem, your brakes should be perfectly capable of slowing you adequately, and unless you do a lot of downhills, brake pad wear should be negligible. Likewise it's not clear that "Akin to motorized vehicle" is an advantage. – Johnny Jun 6 '15 at 1:07
  • it's an advantage because as soon as you stop pedalling, the drag kicks in. And the only time you stop pedalling is when you want to slow down, and you don't even have to modulate your brake (especially when coming at bends) – Nhân Lê Jun 6 '15 at 1:10
  • 2
    I'd count that as a disadvantage since I like being able to coast without pedaling on the flats and downhills. But since some people prefer fixed gear bikes, I can understand why some may see it as an advantage. Though I'd rather be able to control the braking myself (especially on bends on slippery roads) than to have the bike decide how much backpressure to provide through regeneration. – Johnny Jun 6 '15 at 1:25
  • 1
    The two don't have to be mutually exclusive in theory. In practice they might always be. – Chris H Jun 6 '15 at 10:07
  • 1
    In theory the controls could be designed such that regen only occurs during braking, and there would be no trade-off necessary. Some bikes may actually do that (perhaps called "active regeneration" or some such), but I'm not familiar with the details of what's on the market now. – Daniel R Hicks Jun 6 '15 at 11:14
8

Freewheeling is almost always better.

If a freewheel ebike control system fails, it reverts to being a regular bicycle and you can pedal home. Otherwise, you might find that you cannot even push it home if the motor is stuck on heavy regen.

Furthermore, there is very little energy that you can regenerate from a bicycle. There just isn't enough mass or significant enough velocity to make it worthwhile. The regen also makes braking more complicated than it has to be as you need to swap out your brakes/brifters with ones that have brake-switches in them.

On a vigorous discussion on the EndlessSphere forum, Justin Le pulled out data from his cross-country trip. While he did get 18% regen going down mountains passes, he also only got 1-2% regen touring over rolling terrain. His urban regen data was 11% which is close to the 10% figure that is used as the rough estimate of range extension possible.

So, although this is a just from a single run, you could easily conclude that we'd expect about 5% regen for city riding in mostly flat terrain, 10% regen for city riding with lots of moderate hills, and probably more like 12-14% regen if there are really steep hills.

Since e-bikers tend to recharge every day and each recharge is only 1-2 cents of electricity, increasing range and efficiency a modest 10% just isn't as important as it would be with a hybrid or electric car.

  • 1
    Yes, there is very little energy you can regenerate from a bicycle. The advantage I see to regen braking is not the energy recovered but the reduction in brake pad wear. I do not have regen, and I go through about 4 pairs of disc brake pads a year. Suspect it would be far less if I had variable regen enabled. – LifeCycle Oct 24 '16 at 2:30

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.