h a l f b a k e r y
You could have thought of that.
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Regenerative braking usually isnt helpful on unfaired
bicycles <EDIT: or supercapacitor, per bs0u0155 suggestion>,
because if youre going fast most of your
is pushing air out of the way - not enough left to make it
worth trying to
recover braking energy. When it comes time to slow
the energy recoverable to go from 15MPH to 0 is much,
much less than what it took to get you up to 15
This could be adjustable, but by way of example lets set
an arbitrary limit of 12 MPH. Thats enough to cover a
miles in an easy day and not so fast that aero is too big a deal.
Have a speed limiter that could
your speed to 12MPH (perhaps via a generator that
imposes a load
at the pedals or rear wheel), even if you were putting
on the pedals to go faster - instead of letting that go to
the wheels, dump it into a battery. Similarly, if you were
braking, or coasting downhill, recover all that energy.
Then use it feed an assist motor when you need to start
from a stop, or slog up a hill, or in any
youre putting a lot of ergs to the pedals and NOT
even making 12 MPH.
I thought of this idea today while I was blasting down a
at over 40 MPH after slogging UP the approach to it at
around 6 MPH. Enjoyed the payback but lamented that it
really didnt balance because aero drag increases as a
cube function of velocity.
Example of a bike with regenerative braking [pocmloc, Jun 20 2021]
Explanations of why regen is a stupid idea [pocmloc, Jun 20 2021]
Explanation of the law [pocmloc, Jun 20 2021]
Discussion of legal issues [pocmloc, Jun 20 2021]
bicycle with speed governor
Shameless self promotion [xaviergisz, Jun 21 2021]
||I think there are lots of legal issues with electric bikes in general, mainly because they don't fit into established categories (pedestrian or motor-vehicle)
||In the UK, electric assist is limited to 15.5mph.
||Some machines do have regenerative braking, but not many - for general city use I think it is considered an unnecessary additional expense and complexity for very little gain.
||Many manufacturers use powered bottom brackets rather than powered hubs (connected perhaps to legal issues to do with "pedal assist" being the only permitted form of motorisation) which obviously is not suited to regenerative braking at all.
||[pocmloc], thanks for the links. I thumb my nose
at legalisms but they cover some good
tech points. Ive also looked at the Stealth
(covered in your first link) and dismissed it as a
bad implementation. They need my speed limiting
idea to automate how/when to capture braking &
downhill energy - not relying on the rider to push a
button at specific times.
||//limited to 15.5mph//
There are electric scooters here (stand-on style) that will
happily keep up with 50km/h traffic. Not sure about
"normal" bicycles with electric assist (definitely more than
||Oh yes those things are here as well, there's a slight mismatch between what vehicles are popular and practical, and what vehicles are permitted under road and vehicle legislation. But I'm sure in about 100 years time the laws will have been updated...
||//Some machines do have regenerative braking,//
||There is a little complexity, but not much. It's all in the
electronic speed control and is available for not too much
money, Benjamin Vedder's VESC for example. The
problem occurs with the battery. Lithium cells of all
chemistries are picky about charging. I have some cells of
5500mAh that are rated for 100c, that is 550A continuous
draw, amazing really, but they are only rated for a 1c
charge rate. So there is always a limit to how fast you can
put energy back. Supercapacitors would help here.
||Thanks, edited writeup to include that possibility.