Essay, Pages 24 (5898 words)
I have actually added an electrical power help onto a GT mtb. With a 3 HP peak motor, it is far more effective than normal electrical bicycles. The basic motivation to develop an electric bike was to have an enjoyable and efficient and eco-friendly way to avoid my vehicle for short journeys around town, and also as a quiet path bike for exploring the hills. I desired to get some exercise – this bike can still be pedaled. When I initially put this together it was even more of a blast to ride than I had visualized.
I have actually seen 70 years of age people get on this bike and laugh like youngsters – it’s like a magic hand is silently enhancing you along. This site will explain the background of this little electrical car, use some reflections on the electrical and hybrid vehicle scene, and information the majority of the design and motor and batteries must you be interested in making one yourself.
Though it’s a little bit of a project, a number of individuals have actually made very similar bikes based on my fundamental design. The Charm of the Electric Bike.
No sound – no vibration – no smog – no smog checks – no registration – no insurance – no motorist’s license No gasoline – no oil – no tune-ups – no parking inconveniences – no car payments – no more exercise (use the pedals) – no brainer Background: Why construct an electrical bike? Why utilize such a huge motor? I like the concept of electrical lorries in basic and would enjoy to have a pure electric car.
I have a Prius, presently simply about the closest thing offered. Nevertheless, battery innovation hasn’t advanced enough to make a pure electrical cars and truck inexpensive yet.
I do think, however, that light-weight, low-speed, short-range lorries are wellt within the limits of current battery-electric technology, so I set out to see what might be done to make a more powerful and longer-range motorized bike. Since I live about 3 miles from my favourite grocery store and my home is at the top of a relatively long and high hill, cycling and walking is simply exhausting sufficient to be dissuading to me on a spur-of-the-moment basis. Nevertheless I like cycling. I have mountain bicycle and folding bikes.
In looking for a motor to add to one of my bikes, I rode some ready-made bikes and noticed that they are really fun to ride. The silence and effortless cruising along is just magical. But the electric bikes and motor kits for sale at the time, such as the Curry USProDrive, the eBike, etc. were fairly low power and really aren’t that much faster up a steep hill than an unassisted bicycle. The Wave crest was the first decently powerful ready-made bike, though the company didn’t last long. (Electric vehicle companies seem to have a curious habit of making a big splash – and then vanishing beneath the waves.)
Now you can buy decent electric motor kits from Wilderness Energy and Crystallite, among others, but I was curious about the nuts and bolts of things, and wanted to learn more about exactly what it takes to drive a vehicle with pure electric power. I am a great fan of all electric vehicles and watch the new technologies closely. Hybrid cars are a tremendous technology that in my opinion is the first step on the road to all-electric vehicles. Hybrids will necessarily drive the development of better and cheaper batteries, which is the only missing link to the puzzle.
Hybrids of today that are only charged by their gasoline engines will lead to ‘plug-in’ hybrids that can be partially recharged at home or at charging stations. This will lead to astonishingly frugal use of fuel, but these cars will need much larger battery packs, which means better and cheaper batteries will have to be produced. This will happen and is probably happening right now. Eventually batteries will become so much better that the auto companies will start to produce cars that simply leave out the combustion engine altogether – the pure battery electric vehicle.
Don’t get me started on fuel cells and the much hyped future ‘hydrogen economy. ‘ This is interesting technology, but suffice it to say that there are so many technical breakthroughs and logistic problems yet to be solved, that I simply don’t see it happening within the next ten or fifteen years. In other parts of this website and in the Electric Bicycle FAQ, I elaborate a little more on the near and far term technology, where I see it going, and what the most promising developments are. This is not really a build manual, however.. .
Experienced tinkerers may glean a lot of ideas and solutions from my pages if they want to use them and adapt them. There are parts lists and plenty of photos. This driveline is now extremely robust and probably suitable for larger electric vehicles, not just bikes, up to three to five horsepower. Over the course of this project I’ve made many interesting discoveries, encountered issues and problems which all electric vehicle builders must face, and finally figured out some fairly simple solutions.
I’ve fitted a number of different driveline systems which range from simple single vee-belts to the present double reduction using a heavy-duty toothed belt and chain. Earlier versions are shown on following pages. This bike performs well, is stone-reliable and nearly silent, and all the major components are available online or at power transmission supply houses. Note that I had to weld and machine key components like the jackshaft mount using ball bearings, and the chain sprocket that clamps on to the spokes at the wheel hub.
The right components and design solutions to this project were hard to come by, and I just want to share what I’ve learned to promote what I consider a pretty amazing form of transportation. V1. 5 – Dual Reduction Belt/Chain Drive The current version is what I am calling v1. 5, which is the same bike as v1. 4 but with some basic changes: a new timing belt drive system with a chain final drive. Basically, the motor drives a belt that spins an intermediate shaft or ‘jackshaft’ mounted next to the motor and spinning on ball bearings. This shaft then drives a chain going down to the rear bike wheel. Same motor and all other components. (Earlier versions are documented on following pages. )
BASIC SPECS OF V1. 5 * Scott 24 V DC, 1 hp motor (3 hp max) – still available from cloudelectric. com * Gates Power Grip GT2 belt primary drive * 1/2″ steel jackshaft on custom shaft ball bearing mount – 3:1 reduction * #35 chain final drive to rear wheel – 2. 77:1 reduction * 8. 44:1 overall gearing gives top speed of about 27 mph * 2 x 12V Hawker AGM-type lead acid batteries, 13 Ah each; later replaced by B&B 12v 16Ah batteries (also AGM) * 4QD “Scooter 180” speed controller – 180 amp with optional regenerative braking * 24 V charger charges in 2-5 hours typically.
* pedal in all 18 speeds * batteries and motor removable in 10 minutes * range 15 miles on the flat depending on pedal assist * weight 85 lbs. Motor The Scott motor is 24 V DC, brushed, and is rated at 1 hp (746 watts) continuous power and draws 41 amps. It cost about $250, however in 2008 I see the price is closer to $350. This model no. 4BB-02488. This motor is available still from cloudelectric. com. Don’t let the rating fool you, this motor will put out 2. 5HP peak and can even be over-volted (judiciously) to 36V where it will put out 1. 5 HP continuous and around 4HP peak.
If you’re crazy enough to gear it up, it would propel a bike to around 50mph (please don’t do this. ) So the Scott is pretty heavy and suitable for slightly larger vehicles; for a bicycle, a better alternative might be one of the motors at evdeals. com such as the 500 watt 36V motor for only $60. Cloud electric also has a selection of motors from $80 to $170 that would be very suitable according to your budget and power desired. A very interesting choice is their ‘Motor 36 Volt 1000 Watt’ model that has an integral freewheeling clutch. This can also be run at 24V to get 535 watts of power.
(I may have to switch over, these sounds like an ideal motor for a project like this. ) You cannot just use any old motor to drive a bike. People often ask me, can I use a motor from an electric drill, or a starter motor from a motorcycle or a car. The short answer is no, these motors are generally not suitable at all. The efficiency is poor, they will overheat, they are not powerful enough, the speed is too high, they’re too noisy, or any number of other reasons. The Scott is a very high quality motor with high efficiency, good cooling, and ball bearings.
At 16 pounds it is pretty heavy but motors in this power range were hard to find five years ago. If I were doing this today I would undoubtedly use a lighter motor of the type that has subsequently become available. There has been a tremendous influx of scooters and smaller electric vehicles, and many of the motors on these vehicles would be suitable for a bike. There are also a number of motors used by people making combat robots or battelbots. These are generally high power and quite tough. However battlebots don’t really need efficiency so this is something to look out for.
Efficiency of greater that 80% should be looked for at a wide range of speeds and currents. In my opinion, a bike needs a motor of at least 400 watts and probably not more than 1000 watts. Any less and you might as well not bother, and any more and the motor will probably be large, heavy, expensive, deplete your batteries in a flash, or all of the above. The reason for a motor this powerful is simple: hills. I live on a steep hill. While a Zap or a US ProDrive bike rated at 400 watts goes a decent 17 mph on flat land, they slow to 3 to 5 mph on a decent hill. I can pedal that fast.
I have ridden a Schwinn with the Currie US Pro drive. It was actually great, I would recommend it to anyone as a very good turn-key kit solution. However I wanted to go faster and be able to get up a hill. The simple fact is that you need from 5 to 10 times as much power to go a given speed on a decent grade. This is why a car that only needs 12 hp to go 60 mph on flat roads has an engine that can put out 100 to 200 hp. The Scott motor was used in many go-carts and Electrathon vehicles. (Electrathons are efficiency competitions using ultralight closed-course battery electric vehicles carrying one person.
The point is to go the farthest distance in a given amount of time. ) So the efficiency is obviously pretty good. The motor cost $269 total shipped, and weighs about 16 pounds. It has ball bearings and massive cooling fins and is built to last. Brushes do not wear out very fast at all, this is not really a concern. It draws around 41 amps while producing a continuous 1 hp. Put a greater load on it and will draw well over 100 amps and produce up to 3 hp. This is why it needs a 180 amp controller. More about controllers later. Speed Reduction and Gearing: a big issue.
I will spend quite a bit of time here describing the speed re.duction scheme, as this is the most difficult problem to solve in fitting a motor to a bike or other small EV. The big issue with all motorization schemes on bikes is this: how to reduce the speed of a typical motor, which may turn at upwards of 3000 rpm, to the necessary speed of a bicycle rear wheel. A 26″ mountain bike wheel at 20 mph is turning only about 265 rpm. The overall reduction required is therefore between roughly 8:1 and 11:1 depending on what top speed you wish to achieve.
Now it is certainly possible to simply bolt, say, a 130-tooth chain sprocket to the rear wheel and drive it with a 13-tooth drive sprocket off the motor. But this is a very large wheel sprocket (about 15″ in diameter) and, critically, the chain would be unbearably noisy. My basic observation about chain drive is that if any chain sprocket turns faster than about 750 rpm, it will start to make a racket. If only there were a good quiet 3:1 gearbox you could bolt on to the Scott, the final 3:1 or 4:1 ratio could be easily achieved with a chain and sprockets to the rear wheel.
However I don’t know of such a gearbox ready made, and a gear box is very difficult to machine from scratch. Straight cut gears also tend to make a whining noise. This big problem of gearing down the motor has lead to the development of the hub motor. This is simply a bicycle wheel hub with a motor built in, which can then be spoked to a rim. Such hub motors either have gears built in, or they are very particularly designed to just turn at a very low speed while still having good power and torque. This is a difficult trick. It’s much easier to make a motor that derives its power from spinning at higher rpm.
At any rate, at the time I could not find many hub motors, and the few that were available were expensive, made a gear whine, and were underpowered. Also, a hub motor has one set gearing by design, and you can’t alter it. I wanted something where I could experiment with different gear ratios, top speeds, and hill climbing ability. I have come up with this belt drive to achieve the primary speed reduction of 3:1. The dual-reduction drive system is much more solid than anything I have tried before. It’s a little more complicated but slippage is absolutely eliminated and I feel confident that this system would be able to take even more power.
This is important because the Scott motor is often bumped up to 36 volts rather than 24 and I may eventually switch over. Why belt primary drive? Wouldn’t two chains be easier? Basically, as I say, belts are much quieter at high RPM. At 3000 rpm a chain would be about as loud as many small gas engines. An electric bike should be whisper quiet, and this belt drive is. Many electric go-carts use a single straight chain drive; however, they go faster while having smaller wheels, so they need less speed reduction, and the wind and tire noise and speed tend to mask the racket the chain makes. Plus, carters don’t really care much about noise.
I used a Gates PowerGrip GT2 belt. This timing belt has rounded teeth so it’s quieter than other belts. The teeth are closely spaced for better grip on small sprocket wheels. This is the 5mm pitch type. At 25mm wide, the short belt is much less likely to stretch and is easily tensioned by pivoting the jackshaft mount slightly – three of the mounting holes are slotted, so the mount can pivot around the un-slotted fourth hole. Does this wide belt seem like overkill? The Gates Co. has very nice simple little engineering software they give away on their website that will tell you what size and type of belt you will need.
You plug in the power, gear reduction, speed, and a couple of other things and the program will give you some recommendations. I used the program and this was one of the recommendations and what do you know, it has been great. Has never been adjusted and and has never slipped or worn. The jackshaft itself is a 1/2″ steel shaft running on two R8 sealed ball bearings. The mounting plate and bearing housing is welded aluminum. Sorry that I don’t have a diagram of this but hopefully you get the general layout from the photos. If belts are so great, then why chain final drive?
Since the jackshaft is now speed-reduced to 1000 rpm max, running a chain down to the rear wheel now makes sense. There is a reason so many bikes and motorcycles still use steel chain final drive. It makes sense here because the run is longer and the available space narrower, and chain is much stronger and less stretchy than a long narrow belt. At this speed the chain may be slightly audible at top speed, but not noisy, and the wind and tire noise while riding will actually be louder. A chain doesn’t need to be tensioned nearly as tightly as a belt.
Finally, chains have a master link which makes assembly and removal much easier, like when changing tires and repairing flats. (Belts are endless. ) The #35 chain is a very common American size. It has a shorter pitch than bicycle chain but is much stronger. (Bicycle chain is made flexible to allow for the side to side misalignment resulting from different derailleur gear combinations. ) You will notice the extra bar running in between the chain, from the jackshaft to the axle. This is a reinforcement and has an adjuster nut at the lower end to establish proper chain tension.
The bar acts to maintain proper driveline rigidity – the Scott motor can put out a tremendous amount of torque and the motor mount and bicycle frame will twist and compress under heavy power loads without this bar. Actually it attaches to the bike frame near the axle using the stock rack mount on the dropout. The driveline parts are as follows They were ordered from Bearing Belt Chain in Las Vegas at www. bearing. com. * belt:
GATES POWER GRIP GT2 5MR-400-25 Gates part # 9390-8080 $11. 35 * motor sprocket: GATES P21-5MGT-25-MPB Gates part # 7709-5021 $17.
20 * jackshaft sprocket GATES P64-5MGT-25-1610 Gates part # 7709-2064 $30. 52 * sprocket hub mount for above: GATES 1610 1/2″ TAPER LOCK BUSHING part # 7858-1608 * jackshaft ball bearings: MRC part # R8Z $11. 56 ea. (2) * jackshaft: machined from 1/2″ stainless steel stock * jackshaft chain sprocket: #35 chain, 13 tooth MARTIN 35BS13HT 1/2″ bore $6. 91 * rear wheel chain sprocket: #35 chain, 36 tooth MARTIN 35B36 $11. 56 (modified on my lathe to fit) * chain: #35 chain that I had lying around – length is 50 links (100 rollers) – 37-1/2″ long.
A number of machining, fabrications, and modifications I had to do myself. The jackshaft mount is the most elaborate part to make and took some time. The jackshaft and motor need to be very rigidly connected and aligned, yet adjustable to set the belt tension. I used a 1/4″ aluminum plate and welded a 1-1/4″ alum. tube to this. There are two diagonal braces welded to these – you can only see the upper one in the photos. The braces just clear the motor. Then the tube was bored in the lathe for the two ball bearings. It also has ring grooves for retaining rings to hold the bearing in place.
The 1/2″ shaft is about 5″ long, also with ring grooves. There are a total of 4 stainless steel 1/4-20 allen bolts holding the whole thing to the face of the Scott motor using the existing tapped holes. As I mentioned, three of the holes in the jackshaft plate are actually curved slots to allow for adjustment to tension the belt, the whole thing pivoting a little around the fourth bolt. The 21-tooth motor sprocket was bored to 5/8″ on my lathe. It is fixed to the motor shaft with a 1/8″ steel split pin or ‘roll pin’. I had to drill a hole for this pin through the sprocket and motor shaft.
Roll pins are much stronger than set screws, and they are pressed or driven in, so they don’t come loose. They’re also easier to machine than Woodruff key-ways. The large 64 tooth belt sprocket arrived in solid steel and was ridiculously heavy. Aluminum was not available. So I drilled it out extensively to lighten it as you can see. The chain sprocket bolts to the hub of the belt sprocket with two 10-32 allen screws, the holes for which I drilled and tapped. The motor is mounted to the bicycle frame on a specially made 1/8″ thick stainless steel bracket. The whole bracket bolts to tabs welded to the bike frame with three allen bolts.
The chain, drive belt and motor can be removed from the bike in about 3 minutes. Finally, I had to attach a sprocket to the rear wheel. I finally decided to just try clamping a sprocket to the spokes. This may seem like a clumsy solution but I have seen it done on a number of other applications. It has been reliable and has not damaged the spokes at all. Sometimes simple and direct wins the day. For those of you familiar with the Currie US ProDrive, a very popular electric drive kit for bikes, this is basically the same way they bolt their motor plate to the bike wheel.
Looks somewhat unsophisticated? Fine, but it works, bolts quickly to a completely unmodified bike wheel, and has been trouble free. I started by boring out a standard type-B 36-tooth sprocket (the kind with an integral offset hub) to where the hole would just fit around the protruding wheel hub. This locates the sprocket nicely on the hub center. Then I basically faced the hub down to nearly nothing on the lathe, just enough to space the sprocket out away from the spokes. Then I drilled 9 holes for 10-32 screws. The screws go through the spaces where the spokes cross.
I made three curved clamp plates with three holes each for the inside of the wheel. For off-road use I intend to get a different wheel with a knobby tire and a larger sprocket to lower the gearing for better hill climbing. A couple of extra chain links will make it easy to switch out. The net of all this is that finally I have got it really right. I can whack the throttle open and closed at any speed and there will be no belt slippage of any kind. The first thing I did was to go down the street and climb this steep rocky trail that gave the old bike problems.
Even with the relatively high gearing, the new driveline shot me right up the thing. I even popped a little wheelie over the top of it. That sure never happened before. Now I can finally use all of the torque this Scott motor can put out.
DESIGN & COMPONENT DETAILS BATTERIES
There is no question that the battery is the single thing, the one and only, overriding thing, that is holding back the development and mass proliferation of electric vehicles. At this point in time most of us are still stuck with using lead acid batteries. I am now using B&B 16 Ah batteries, made in China.
Originally I used Hawker Odyssey batteries model PC545, 12 lbs. each, which are basically the same as the Hawker Genesis G13EP. All of the batteries I have used are deep-cycling, AGM (Absorbed Glass Matt) sealed lead acid batteries (SLA) and are about the best quality lead acid battery available. They can be mounted in any position except upside down and they are sealed and maintenance free. They are much like the Optima batteries used in many advanced electric vehicles like the EV-1 and the Sparrow but are available in a wider variety of smaller sizes. I got them at Thunderstruck-EV. com.
They now run about $50 each. It is nice that there is some competition now in this type of battery and the prices are coming down by about half from what I paid for my first set. Of course lithium ion batteries of some kind would be the great enabler. Lithium is just now entering the market, they are still quite expensive and something of a question mark. Conventional lithium cells, as used in laptops, have a thermal runaway potential – meaning they tend to catch fire, in some cases like a Roman candle. New materials and chemistries based on lithium are attempting to address the safety problem.
I have seen batteries called LiFePo4 – lithium iron phosphate – offered for sale at various websites selling electric bikes and accessories. They are claiming no fire problems, At this point, it looks like a decent battery pack for a bike like this would cost around $1000 or more. That is a lot of money to spend on a battery with a 1-year or 2-year warranty. In my opinion, these batteries need to come down to the sub-$300 range before I would really be interested. A battery is rated in voltage and amp-hours. Voltage times amps times hours equals watt-hours and this is the total energy available from the battery.
So my battery pack has 2 x 12V x 16Ah = 384 watt hours. In other words it will give 384 watts for an hour. But actually, it won’t. The “16 Ah” is a rating to be taken with a very large grain of salt. An essential thing to know about batteries is that they give a lesser amount of total energy when discharged at a high rate. Read that last sentence again and absorb it, it’s important. A battery’s electrical power is not like a glass of water. If you drain that glass quickly or slowly, it contains the same amount of water. Batteries, not so. Draw high amperage, and your total amount of energy is less!
Because of this, batteries are often rated nominally at a slow 10-hour discharge rate, in which case they will give more total energy and thus seem like a better battery. Bikes and all electric vehicles use energy at a very high rate. A bike can easily draw enough current to discharge a battery pack fully in under half an hour, so batteries will not give their rated output under these conditions. Another tempting choice for cheap batteries might be Panasonic or Powersonic or Sonnenschein gel-cell /lead acid batteries. Gel cells are the typical batteries that come with most stock electric bicycles and kits.
They are not AGM. Longevity is not as good, though the stated juice per weight ratio seems better, and they are available in a variety of smaller sizes if weight were more of an issue than range. Hawker makes slightly larger AGM batteries such as the G16EP like my B&B which have a little more juice but are also heavier. The Hawkers are very well made. Another great thing about AGM type batteries is that they can be charged quickly at much higher amps than other kinds of lead acid batteries. Likewise they have the ability to give high current with no problems.
AGM batteries are also unique among almost all battery types in that they retain a full charge for months with no ‘charge leakage. ‘ One of the big drawbacks of of NiMH batteries is that they discharge about 1% to 2% per day. Regular lead acid batteries will just go dead in a few months as well. Because of this, AGM batteries are also marketed to people with antique cars and snow plows – vehicles that aren’t used very often and are likely to have a dead battery when you finally want to start it up. All lead acid batteries have two big drawbacks. They are quite heavy for the total amount of power they deliver.
And even these so called “deep cycle” batteries really should not be deep-cycled too often, as repeated deep discharging dramatically shortens their useful lifespan. This is where NiCads have lead acid beat, as they are more power dense and can be run down pretty much all the way without much damage. Of course large NiCads are much more expensive and must be recycled carefully due to the toxic cadmium. So until better batteries like NiMH or Lithium Ion are more widely available in vehicle sizes and less expensive, Hawkers and other AGM type lead acid are about the best we can do.
More ruminations on the Great Battery Quest below. Batteries and 120 amp speed controller mounted in the main frame space.
A speed controller or motor controller is essential in applying the voltage and power that is delivered to the motor from the batteries. All decent electric vehicles need a motor controller of some kind. On a bike with a very small motor it might be possible to just have an on-off arrangement, and I suppose there are other less expensive and much cruder ways to control speed but I feel that a decent controller is absolutely necessary with a powerful motor like this.
The controller is a rather expensive electronic black box with no moving parts. A modern PWM or ‘pulse width modulation” controller is very reliable as long as it’s current limit is not exceeded. Unfortunately a high ampere capable controller is not cheap and may cost about as much as the motor. Curtis controllers are well known in golf carts and other industrial vehicles, however I am using a Scoota 180 amp speed controller from 4QD. – www. 4QD. co. uk . This is a small company in England, that specializes in smaller and cheaper controllers for light electric vehicles. The controller with a matching thumb-lever throttle was $248.
It is capable of regenerative braking, thought you can easily disable this function. Previously I tried a Scoota 120 amp model that was nearly identical. It failed after a few months. I was just working it too hard and the output connections overheated and melted. The 4QD factory has a nice policy of repairing their controllers and exchanging them for different ones if you want, with a very fair exchange allowance. The new 180 amp model gets a little warm but has been quite dependable for well over three years now. I originally used an Eagle 80 amp controller from the same company. It was $120.
It failed due to overheating but that was completely my fault for using a much too-small controller. If I lived on flat terrain I think it would have been fine and would have lasted a long time, especially since I added a finned aluminum heat sink from an audio power amplifier – try a decent electronics store, maybe even Radio Shack. You need to size your controller at about 3 times the rated power of your motor. My motor is rated at 41 amps continuous, HOWEVER it will draw a lot more than that at full throttle under load. Manufacturers tend to state their controllers at intermittent current limits.
For example a Scoota 120 will put out 120 amps for a short time but should not be run that high continuously. Regenerative braking – nice idea but . . . 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 region set up for maximum regeneration, the throttle can be quite touchy. And if you just suddenly release the throttle, which is fairly normal behaviour, 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 your 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. 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 ebike was just slowing me down and creating heavy backloading 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 EVs and hybrids have als.