Regenerative Braking -
If you really want to know!
This guy has the answers to the most common questions and them some. He doesn't sell anything, he's not promoting anything.
A lot of people inquire about regenerative braking. Hybrid car manufacturers often tout the ability to reclaim electrical energy when the car is going downhill. I don't know how much energy they are getting back in a car, but on a little electric bicycle, it is almost certainly never worth the added trouble, expense, and operational hassles. You would be much better off with a freewheeling setup. Let me explain how I've come to this conclusion. The speed controller I use has regenerative braking available.
After trying it out for a while, adjusting it and testing it every which way, I ended up disabling it. Regenerative braking means that as you brake or coast downhill the controller will use the motor in reverse as a generator to re-charge the batteries. On my route to the market, for instance, I am on flat terrain for a while and then go downhill for about a mile to reach the store. Conceivably this could mean that I arrive at the store with nearly full batteries, which would make the ride back less likely to drain the batteries completely. However, the regenerative braking is a function of the speed controller.
If you have the regen set up for maximum regeneration, the throttle can be quite touchy. And if you just suddenly release the throttle, which is fairly normal behavior, the braking effect would be full. It is really not very good to have the throttle set up to brake that hard. I found myself about launching over the handle bars every time I lost forgot and snapped the throttle off. Also, this is a good way to have other people ride you bike and crash it.
Note there is no freewheel on the electric side of my bicycle. A custom freewheel is yet another surprisingly difficult mechanical part to machine or to buy. Of course the pedal-drive freewheel still works, which means that you can motor without the pedals being forced to turn. However, it you pedal the motor will necessarily be turning, which is a drawback if the batteries die. The regenerative braking function requires a solid connection to the wheel. However, after some time with this bike, using the regen function of the special speed controller, I came to a surprising conclusion against using regen. As I say I bought a controller with regenerative braking. With this set-up, I could basically use the thumb-throttle carefully as a fairly powerful rear brake.
The amount of braking could be adjusted to make it less grabby, but I never could get it to the point where I liked it at all. It was obtrusive and difficult to control. I suppose if you could hook it up to a pressure sensitive brake lever, it would work better, however, that is a bit beyond the level of sophistication I think is really necessary on a little electric bike. Luckily the regen function can be defeated which is what I finally decided to do.
Realize, all vehicles are "regenerative" going down a hill.
Note there is no freewheel on the electric side of my bicycle. A custom freewheel is yet another surprisingly difficult mechanical part to machine or to buy. Of course the pedal-drive freewheel still works, which means that you can motor without the pedals being forced to turn. However, it you pedal the motor will necessarily be turning, which is a drawback if the batteries die. The regenerative braking function requires a solid connection to the wheel. However, after some time with this bike, using the regen function of the special speed controller, I came to a surprising conclusion against using regen. As I say I bought a controller with regenerative braking. With this set-up, I could basically use the thumb-throttle carefully as a fairly powerful rear brake.
The amount of braking could be adjusted to make it less grabby, but I never could get it to the point where I liked it at all. It was obtrusive and difficult to control. I suppose if you could hook it up to a pressure sensitive brake lever, it would work better, however, that is a bit beyond the level of sophistication I think is really necessary on a little electric bike. Luckily the regen function can be defeated which is what I finally decided to do.
Realize, all vehicles are "regenerative" going down a hill.
Turning the engine off down a long hill in your car and coasting - this is reclaiming the energy spent to climb the hill. Unless the vehicle is very heavy and/or has great aerodynamics, most of the energy going down a hill will just be used to overcome air resistance, with little left over to recharge the batteries. Normally on a bicycle, very little braking is ever necessary, and top speed down most hills is quickly limited by poor aerodynamics. The net result, I felt, is that the regen on my e-bike was just slowing me down and creating heavy back loading on the drive train needlessly. It would be better to put the motor on a freewheel and adopt a method of getting up to speed and coasting as often as possible with the motor shut off. This riding technique is apparently very effective at extending your range, probably more so than having regen.
Many people who deal even with larger E.V.s and hybrids have also formed the opinion that a pure freewheeling function would be better in many instances than regenerative braking. The regenerative braking function of hybrid cars, for instance, is vastly overstated. Hybrids work by generating their electric power onboard using the gas engine; they have a power generation function built-in, it is central to the entire concept. So why not use it for braking as well? Sure, but in reality this produces very little in the way of reclaimed power. The batteries in hybrid cars are charged at least 95% by the using the gas engine as a generator; and the reason they are so efficient in city driving is simply because they can run at slow speeds very efficiently on predominantly electric power. It is only while driving at higher speeds down long steep grades that any decent power is truly regenerated to the batteries. How much of this describes typical driving conditions?
Coasting with minimal drag from the motor is actually much more efficient. While coasting the vehicle uses no juice whatsoever. It is common practice during mileage or efficiency runs with a hybrid like the Honda Insight, to accelerate to speed, then go into neutral and coast for a while.
Many people who deal even with larger E.V.s and hybrids have also formed the opinion that a pure freewheeling function would be better in many instances than regenerative braking. The regenerative braking function of hybrid cars, for instance, is vastly overstated. Hybrids work by generating their electric power onboard using the gas engine; they have a power generation function built-in, it is central to the entire concept. So why not use it for braking as well? Sure, but in reality this produces very little in the way of reclaimed power. The batteries in hybrid cars are charged at least 95% by the using the gas engine as a generator; and the reason they are so efficient in city driving is simply because they can run at slow speeds very efficiently on predominantly electric power. It is only while driving at higher speeds down long steep grades that any decent power is truly regenerated to the batteries. How much of this describes typical driving conditions?
Coasting with minimal drag from the motor is actually much more efficient. While coasting the vehicle uses no juice whatsoever. It is common practice during mileage or efficiency runs with a hybrid like the Honda Insight, to accelerate to speed, then go into neutral and coast for a while.
This actually produces the greatest mileage and efficiency. On an electric bike it is undoubtedly most efficient to pulse the motor on till you get up to speed, and coast on downhills, or pedal on the flat to maintain speed. Having the motor freewheel would be a big advantage.
Http://www.Pegasuspowersystems.com Questions? email to Dalesbest4bikes@aol.com
Http://www.Pegasuspowersystems.com Questions? email to Dalesbest4bikes@aol.com
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