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the most commonly asked questions

GUIDE TO BUYING AN E-BIKE

Guide to Buying an Electric Bicycle

If you have decided to buy an electric bicycle, that’s great. I’ll do my best to help you.
If you are just curious or thinking you might buy an e-bike think about reasons like saving money, enjoying life, but above all think of an extra 10 years of good and happy health and good mobility, and that’s priceless. I have pages here to add a bit of gentle persuasion.

In case you did know realise it, you can DIY convert most bikes to be electric bikes. There’re many YouTube videos about doing that.

Warnings

2nd hand e-bikes on e-bay, garage sales and ads.
As increasing number of e-bikes become a few years old there will be more 2nd hand bikes for sale.
These will be cheap but beware that the battery may need to be replaced. It is quite likely that the main reason that the bikes are for sale is because of the expense of getting a battery replacement. As batteries get older the distance they can take you gets less. An old battery can be charged and “going” but will die in a short distance.

So if the bike is “going” make allowance for replacing a battery, and find out from where you can replace it. If the bike is not “going” do make a good assessment of what will be needed. If you can’t do that talk to someone who can.

Replacement parts, especially batteries and controller
These are the parts most likely to fail, and also the parts most difficult to replace. Some batteries are quite “generic”. That is their shape and means of fixing is the same for some different bike brands. These are easier to replace even if some things such as input and output sockets are different. Some batteries are specific to a bike brand. (That is a battery has to be a battery FOR that bike.)

Imported e-bikes are imported with a battery installed in the bike of course. Replacement batteries are expensive, and quoted prices vary a lot. Importing batteries by air freight is expensive, and an importer has to order many in a shipment or pay a premium for one or a few.

You should ask whoever sells your bike these questions about replacement batteries :

  • are they generic or specific to the bike?
  • are there replacements in stock, or available quickly, and what do they cost?

Controllers for the motor are usually different from one brand to another, and often from one model to another. They look similar but there are very many different arrangements of the sockets for the many wires coming from and going to them. I know this is a problem because many people ask me for a controller for a bike they bought from somewhere else.

A motor should last many years. Unless it is a unique design they could be replaced by a similar generic motor.

Other electric parts, throttle and brakes, are usually generic and replaceable.

The non electric parts are usually replaceable by any bike shop, though many bike shops are loathe to fix e-bikes (that will change).

Is the bike legal?

On the road power must be less than 200 watts, or 250 watts if it has no throttle.
A fueled motor must be registered as a moped.
Last year Australia changed its E-Bike rules to match those of Europe.
The effect of the new rules is that :

  • Bikes already in Australia that comply with the old rules can be used.
  • E-bikes now cannot have a throttle independent of pedallling.
  • Pedalling faster than 6kmh is necessary and assistance must cease at 25kmh.
  • Allowable continuous power output is increased from 200 watts to 250 watts, subject to those provisos.

For more about the laws see the new laws or see EN 15194

Electric Bicycle Frames and Styles

Selecting an electric bike to buy is no different to selecting an ordinary bicycle, except that they have a motor to help you and some controls for the motor.
You should keep in mind your preferred style of riding and what you will use the bike for.

Heavy or light?

This is the major factor. A light electric bike weighs about 21 Kg. A heavy one weighs about 38 Kg. That is a big difference, and it is very noticeable.

Why such a difference? The main reason is the battery. A 36v lead-acid battery weighs about 14.5 Kg and a 36v lithium battery weighs about 4 Kg.

Bikes with lithium batteries usually have a light aluminium alloy frame.

Bikes with a lead-acid battery usually have a heavier steel frame.

All electric bikes are heavier than a similar non electric bike would be. The battery and motor are quite heavy. Usually about 9 Kg.
E-bikes with lead-acid batteries.

They make a lot of electric bicycles in China. More than 25 million each year! But about 90% of them are heavy bikes with lead-acid batteries. Why ? Because they are cheap, very cheap in asia,
so nearly all electric bikes there are the heavy ones.

Several million of the lighter electric bikes get exported to the rest of the world – because that is what they prefer there.

I used to have both types but found that if I offered two similar style bikes side by side : one heavy, and one light, customers preferred the light ones – at twice the price. So, I don’t have the heavy ones any more. Very few people wanted them.

There are some heavy e-bikes about. Any new electric bike selling for less about $700 is probably a heavy one (a 36v lithium battery costs about $400). They are cheap but heavy.

A warning about their batteries. They don’t last as long as lithium batteries. The battery case will probably be specific the the brand of bike. If so, the case will probably be hard to replace unless the place you buy it from has spares. If so and if you need to replace the battery you will probably need to replace the batteries within.
The batteries inside are 12v brick shape batteries wired in series.
The 12v batteries are very cheap in China, and are imported installed in a bike. Replacements can be bought at autoparts and battery shops, but are much more expensive to buy in Australia.
They are much smaller than a car battery but not so much cheaper.

Lightweight electric bike frames

The frame shapes of electric bicycles are similar to those of ordinary bicycles. You can get (just about) whichever type suits you…
(If you don’t know which that is, you should try a few friend’s bikes).

If you sit and watch the stream of bikes in Amsterdam, or Copenhagen, or other big bikey european cities you will see that nearly all the bikes are “city” type bikes and that the riders are sitting upright. I think that as more people here adapt their ways to bike riding “city” style of bike will become more common than “road” or “mountain” bikes, especially for short rides, or commutes.

Of course anyone who has difficulty get over a frame with a high bar will like the city or “step through” frame.

If you are very style conscious there are some very stylish, and very expensive, electric bikes coming from european designers…and some cheaper California inspired “cruisers” from China.

Also worth considering are folding electric bikes, which are most commonly “city” style with smaller (20″) wheels.

Folding Electric Bikes
I am finding that folding electric bicycles are becoming much more popular because many people either do, or plan to take the bikes on their travels in their car, or mobile home.

They can stow them easily and don’t need an expensive bike carry rack. Not only that but they stow away in home or office and can be taken on a lot of public transport. Those who
“don’t like” folding bikes can just forget that they do foldup until they need to be folded up.

Range – how fare does an e-bike go?

The energy available (which translates, other factors being equal, to how far you can go) is proportional to voltage V of the battery X the Ampere-Hour (AH) of the battery. The most
common combination is 36v and 10AH and this battery is suitable for motors up to 500 watts.
There are some 24v 250 watt electric bikes, which are 1 or 2 kg lighter but have range about 2/3 of the 36v bikes.
As a rough guide a 36v battery in a 250w electric bicycle going about 25kmh should go about 35-40 km.
The bike factories in China quote a “range” for their bikes, and bike shops generally quote that range in their description. I find that this quoted range is usually quite optimistic – possibly because they assume people will extend the range by pedalling.
Of course, you can extend the range by pedalling, and I hope you do, and get that beneficial exercise, but comparisons should be made on what the is range with battery alone.
There are many factors that affect the range of a bike. These are mentioned in Notes below.

Electric bicycle motors

The cheap and heavy electric bikes common in asia usually a have brushed motor.
Brushed motors are a little bit cheaper. The lighter more expensive electric bikes would now have “brushless” DC motors, commonly called BLDC.
There are 2 types of BLDC motor – larger diameter motors that are (internally) ungeared and have power from 300w to 1000w, and more compact motors have internal gears (that make a low whirring sound) and have power up to 300w. The bigger ones are about 2kg heavier and run more silently.

E-bike Power

Bikes, and conversions, can have motor power from 200 watts to 1000 watts. The higher power 1000w motors should (sometimes must) have 48v battery.
Depending on what country you are in anything above 250w may be illegal (on a road).
In Australia, for instance, the legal limit is 250w whereas in US it 750w, and other places are either in between, or don’t care.
There is some confusion about the “watts”. The chinese suppliers quote the motor’s power as watts of “input” and most bike shops repeat the input watts in their description of the e-bike. The authorities regulating these are concerned about “output”.
This matters particularly in australia where the limit is 250w “output”.
Electric motors do not have a fixed upper power limit and the output power can exceed nominal power. A higher voltage gives higher power. All motors are somewhat inefficient, ie they lose energy between input and output, and the electric motors are at best 80% efficient.
The cost difference between low and high power motors is very little, but the cost of batteries to support them does vary – roughly in proportion to V x AH, higher V and/or AH being needed for high power motor.

What power of bike would be suitable for you?

For most people and most purposes – that is travelling about 25-27kmh on ordinary streets and roads in ordinary suburban terrain a 250 watt bike is quite adequate.
Suggestion : If you do ride an electric bicycle that has more power than is allowed, do, at least, pretend to be pushing on the pedals.
(Better still, do push on the pedals, and get that very beneficial exercise)
For comparison between your efforts and the bikes’s power – 250w is about what you can produce if you are reasonably fit. If you are a competition road cyclist you could put out twice or more of that- but you wouldn’t want to go electric would you?
(If you are on a 500w bike and overtake a road cyclist on a hill please be polite.)

The cost of an e-bike?

The prices quoted for electric bicycles varies a lot. Generally $1300 to $2500 for an alloy frame, and about half that for a steel frame.
The Chinese are not concerned about recommended prices so beware of any fictitious “save $$$” on RRP. (nothing much sells for recommended price these days anyway)
Compare like with like. The quality of components varies a lot…within China, and more so when they use parts from Taiwan instead of Chinese parts.
Compare frame features such as whether the fork has dampers, the handlebar post is adjustable. Compare also quality of, or presence of items such as basket or rear rack, front or rear lights, seats, mudguards, chainguards, tyres and tubes (brand, thorn resistant, reflecting strip). The cost difference between a good and inferior – say pedal or seat – is not a lot in China, but they do try to have a cost advantage over one another rather than a quality premium, so look for quality parts.

E-bike Batteries

Batteries are the most expensive component in an electric bike, about 40% of the total.
There has been, and I believe still is, a very big difference in the performance of batteries between the many places that make them.
Eventually I hope the lesser quality ones will get weeded out, and the better quality makers will increase business. The batteries all look the same, but one doesn’t know how long or how well they will go until they have, or have not, done or gone as they should.
There are several formulations generally called “Lithium-ion” or “li-ion” and others with LithiumIronPhosphate (or LiFePO4, or LFP) cathode.
The li-ion and LFP batteries are usually quoted as having a “life” of 800 and 2000 charges respectively. This quoted “life” comes from the battery supplier who may (or may not have) at some time done a test on a battery. Such test would have been done by rapid repeated charge/discharge cycles until the battery’s energy was reduced by 20%.
In practice, in real use, you may get half of that, but in any case the LFP batteries should last twice or more as long as li-ion batteries because they are much more resistant to the things which degrade all lithium batteries, vibration and shock, (especially) heat, and time itself.
LFP batteries are not common (probably because of cost saving by the factories), but are becoming more common. Even though the energy contained is a little less than in a same size li-ion battery and that they cost more it is worthwhile getting LFP batteries.
However, LFP is a bulkier cathode and any size of battery will contain less of it (and thus energy/distance) than a similar sized battery with Li-ion. For instance 11AH Li-ion and 9AH LFP are often the same size and A 10AH LFP battery will be taller than a 10AH Li-ion battery.

E-Bike Controls

Outside of Europe (where they can’t have one) electric bikes will most likely at present have
a hand throttle. There may be some now, possibly made for europe, that don’t have a throttle.
These will have “pedal assist” or PAS. With this starting, or stopping, pedaling turns the motor on, or off. An improvement to PAS, which many bikes have now is selectable amount of “assist” which you can vary by a handlebar mounted electronic device.
Many bikes will have both PAS and throttle. And that’s nice…but maybe illegal.

And now a word about how the “assist” works.
It does not matter whether your bike is powered by the front wheel or the rear wheel, you can add your own effort to the going, but only if you “get ahead” of the motor, whatever speed it is going. What I mean by that is that you need to pedal faster than you would to go at the same speed if the motor was not working. When you do that you put some tension in the chain. The motor “notices” that and reduces its output.
The more effort you make the less the motor makes until it feels it is not needed, and then you will be doing all the work.
All electric motors have a maximum possible speed, and an optimum efficiency range (rpm) about the middle half (about 1/4 to 3/4 of the maximum) within which they will be operating close to their maximum efficiency. On hills at speeds lower than about half the maximum speed it is best if you add enough power of your own to maintain that speed (using the gears). If the motor slows down and “struggles” it will be sucking a much larger current from the battery. This will shorten life of the battery, and may cause the controller to burn out.

Benefits to you? A lot!

If you need convincing think of the benefits…
Good for the environment, and saves you money, and most important of all – good for YOU!
Whether you go for a walk, or ride a bike, a small amount of daily exercise has a huge effect on your health, fitness and happiness in later life, and has been shown to add years to your life compared with a sedentary and sitting down lifestyle.
A win-win for all, don’t you think? Go find a good electric bike, and start enjoying it!

Notes

Gears, or not for an e-bike?
Most electric bikes have at least 6 gears and one chainwheel cog.
Most of the time (if the power is on) you won’t need more than the top gear or two anyway.
Unless you will be a serious unpowered cyclist some of the time you won’t need 18 or more gears – 6 will be more than enough.

The speed?
Generally the smaller 250W motors will have maximum speed on flat streets of about 25-27kmh.
A 500W motor would travel about 5 or 6kmh faster (not twice as fast). The maximum speed is not directly proportional to power, but is more closely proportional to power when climbing hills at slower speeds. (Because wind resistance increases rapidly at higher speeds and eats up the extra power, whereas the energy needed to fight gravity is proportional to speed).

The range?
The range of an electric bike depends on…
The bike, the battery, the terrain, the ride, the day, and you, it’s rider :

  • 1.The bike….it’s weight, its condition, whether the tyres are fully pumped, and whether the wheels spin freely, and the brakes don’t drag.
  • 2.The battery….its voltage, its AH, the ampere-hours, and its age…(the product of the V and the AH is watt-hours, and that is the energy available to make the bike go, although there will always be some energy left that can’t be used). The capacity of any battery reduces with its age (more so with li-ion, less so with LFP).
  • 3.The terrain….hills have a very big effect.
  • 4.The ride….the speed, the stopping and starting.  Any use of brakes destroys energy that first came from the battery and has to be replaced to get going again. The distance that you would have gone if you coasted to a stop is that much less range – possibly up to several hundred metres. The get-going reduces range because the motor is inefficient at low speed. At full speed the range could be a third less than it would be at around two thirds of max speed – because the efficiency of the motor is much less when it is running close to its maximum speed.
  • 5. The day….less if it’s windy, or very cold and
  • 6 you, the rider…how much effort you contribute yourself – As a guide, a fit cyclist could sustain about putting out energy of about 200W, and the more energy from you the less is needed from the battery.

Tips for getting a greater range from battery.

  • 1. keep tyre pressure up (this also reduces the chance of a puncture)
  • 2. accelerate slowly, and
  • 3. anticipate stopping and use the momentum to glide to a stop.

FAQ QUICK ANSWERS

FAQ-QUICK ANSWERS

  • No, you do not need to register your electric bike (some provisos ).
  • No, you do not need compulsory third party insurance.
  • No, you do not need a car or moped license.
  • Yes, normal bicycle rules apply : yes to helmet, hand signals, bike lanes, lights at night. No to anywhere a bicycle is not allowed.
  • Yes, the bikes have a battery strength indicator so you will know when battery is nearly flat.
  • No, it does not matter at what stage you recharge the battery.
  • Yes, you can recharge it from a powerpoint as you do for a laptop computer, and with a similar charger.
  • No, it doesn’t matter if it rains while riding (no more so than for an ordinary bike).The electrics are sealed and water runs off the battery and motor. Of course one has to be careful with wet roads but puddles or wet roads are not a problem because the bike is electric. Just avoid deep water, (not close to controller box).
  • Speed? Up to about 25kmh, or about 10kmh faster than most people ride an ordinary bike.
  • Price? That depends more than anything on the batteries. There are two types : lead or lithium. Lead is heavy and cheap, and usually comes with a heavy steel frame, and so e-bikes with lead battery are cheap, but heavy. Lithium is light, and usually come with aluminium frame, so e-bikes with lithium battery are much lighter, and to be light is worth much more.

HOW MUCH POWER IS NEEDED FOR HILLS

HOW MUCH POWER IS NEEDED FOR HILLS
More power does not give proportionally higher maximum speed but it does mean more speed going uphill. Just as with a car’s motor in any gear there is a speed range where the motor performs most efficiently while at much lower or higher speeds the motor will either struggle or max out. Electric motors have various performances,
as fuelled motors do.
As you travel the three main forces you have to overcome are wind resistance, rolling resistance and gravity. The least is rolling resistance. The effect is like you are constantly riding up a gentle slope. If you roll down a gentle slope at a steady speed (not gaining) then that slope is the rolling plus wind resistance at that speed.
Bearings condition, brakes rubbing and low tyre pressure affect the rolling.
Wind resistance goes up rapidly at increased speed. 50% faster causes about twice the wind resistance. As does sitting upright. That’s why racing riders tuck down low.
Power needed for climbing hills is of course proportional to the slope.
Neglecting other resisting forces you can work out approximately how much power you need for a hill :
Watts = weight (kg) x speed (M/sec) x 9.81 x gradient (%)
or 100kg at 20kmh at 5% (maybe that’s 4% hill + 1% w+r) = 272W
100kg at 28kmh at 7% (maybe that’s 5% hill + 2% w+r) = 534W
That is approximately what you can expect from 250W and 500W motors.
Note that wheel size and torque are not in the equation.
There is some confusion (and people trying to confuse) about power and torque.
It is power that gets you up a hill, not torque.
Smaller wheels and/or a motor driving the chain, along with lower gears may allow a motor to work more efficiently and so provide more power.

HOW MUCH ASSISTANCE

THE AMOUNT OF ASSISTANCE
We (in Australia) used to be allowed to have 200 Watts of assistance. That has now been increased to 250 Watts, with some provisos. These are that a throttle is not allowed above 6kmh and the assistance must stop at 25kmh.
As a comparison a reasonably fit cyclist can sustain 200-250 Watts unassisted. (A Tour de France cyclist could manage double that,  and for 4 hours, but not you or I).
So what can 250 watts do? On a flat road 250 watts will go about 25kmh, and of course less on hills, depending on the slope. On a moderate hill (about 3 or 4%) the motor alone may slow down to about 15kmh.
You should not let the motor slow down any more than that because it will be running inefficiently and taking a much higher current from the battery, and that will reduce battery life.
You should pedal at least enough to keep the speed up to, or more than, 15kmh. If you have gears you should be able to get up most suburban hills, with you helping the motor. And you will do that several gears faster than you would without the motor.
Extra power does not give a proportional increase in speed – because wind resistance increases rapidly, and motor loses efficiency at higher speeds, but on hills at lower speeds the extra speed is more nearly proportional to the extra power.

E-BIKES RANGE or HOW FAR WILL THEY GO

HOW FAR WILL AN E-BIKE GO ?

…On one charge of the battery

That depends on…
The bike, the battery, the terrain, the ride, the day, and you, it’s rider

  • The bike….it’s weight, its condition, whether the tyres are fully pumped, and whether the wheels spin freely, and the brakes don’t drag
  • The battery….its voltage, its AH, the ampere-hours, and its age…(the product of the V and the AH is watt-hours, and that is the energy available to make the bike go, although there will always be some energy left that can’t be used). The capacity of any battery reduces with its age and treatment (a separate topic)
  • The terrain….hills have a very big effect. Going slowly up a hill causes a bigger drain on the battery than going fast on the flat.
  • The ride….the speed, the stopping and starting. Accelerating fast causes a bigger drain on the battery than does getting going more slowly. Frequent braking wastes the energy that got you going. Going at moderate speed could give about one third more range than going at full speed (and vice versa).
  • The day….less if it’s windy, or very cold and 
  • You, the rider…how much effort you contribute yourself - As a guide, a fit cyclist could sustain about putting out energy of about 150-250W, which is comparable to the motor’s usual 200-250W. However it doesn’t work like 200W from the motor plus 200W from you, because the more effort you make the less the motor makes.     

Tips for getting a greater range.

1. keep tyre pressure up (this also reduces the chance of a puncture)
2. accelerate slowly, and
3. anticipate stopping and use the momentum to glide to a stop.

 

E-BIKE-BENEFITS

WHAT ARE THE BENEFITS OF AN E-BIKE ?

TO YOU

Your health and fitness and weight now , and extra years of  good health and mobility in later years.

Your convenience, especially for short trips.

Your big cost savings compared with car or public transport.

TO THE ENVIRONMENT

A lot less CO2 (and other noxious stuff) in the air, and more fuel staying in the ground

  • 2 cents/km compared with 30+cents/km
  • Not paying $3.40 for even short bus/tram trip
  • It’s so easy to ride, you will ride, and you will enjoy it
  • Medical experiments prove that moderate regular exercise does greatly extend longevity and active and happy good health.
  • Get exercise while getting to where you want to go, gentle or hard, as you choose

 

E-BIKE RUNNING COST

THE COST OF RUNNING AN ELECTRIC BICYCLE

Every kilometre you ride an e-bike saves you 20 cents or more if your alternative is to drive a car. Putting that aside let’s look at actual cost.

The battery needs to be topped up. A typical battery is 36 V (volts) and has current delivery of 10 AH (Ampere Hours, ie 10A for 1 hour H). The energy content of the battery is one times the other. That is 36 x 10 = 360 watt-hours or 0.36 kwh, the units on your power bill. One kwh costs about 28 cents now, so  0.36 kwh costs 10c. Actually we need to add about 30% to allow for losses in the charger and for the battery voltage being actually about 42V . Say 13c. If that takes you 40 km then that’s 0.3 cents/km.

That’s small but the greater cost is allowing for eventual replacement of the battery. If you get 750 recharges of 40 km and a new battery will cost $360 ( I expect battery costs to go down) that comes to 1.2 cents/km.

Tyres, tubes and maintenance may cost 0.5 cent/km. ( you would be paying that to run an ordinary bicycle anyway – same for insurances etc), So cost to run an electric bike is about 2 cents/km

E-BIKES THE PAS

E-bikes -the PAS assistance
Just about all electric bicycles in Australia have had “pedal assistance”. With that control the motor kicks in when you have started pedalling and turns off soon after you stop pedalling.

The simplest control for that is a cadence sensor. This is a small sensor on the bottom bracket. Close to that would be a disc with a ring of magnets on it. As the pedal turns the sensor with detect the magnets moving. Some controllers will measure the rotation speed the pedal and increase or reduce the level of assistance – in steps. Some will just detect the pedal moving or not moving and will give assist or not assist.

Some controls are not very subtle. Sometimes when you just want to give the bike a nudge or to dawdle to manoever the PAS will give you a sudden surge which you were not expecting. The better ones only activate after several turns of the pedal. On the other hand, if you do want a quick take off you need to pedal hard. A throttle was (is) useful for that.

Many e-bikes now come with a handlebar device with which you can select the amount of assistance that the PAS will give you, and you may be able to turn it off. The control may reduce the speed at which the motor cuts out, or reduce the power available.

On the more “top end” e-bikes, particularly european ones, there will be a more sophisticated sensor that measure your actual effort by measuring the strain on the frame or the torque you apply to pedals.

Up till 2013 we had another means of varying the assistance from the motor : a common throttle. That’s not the case anymore… unless the bike has power not over 200 watts.

The europeans, particularly in Holland or Germany, like riding their bikes, so when electric bikes came it was decreed that the motors should only “assist” the rider and not drive the rider. And so it was that all european electric bikes must have assistance only when they are being pedaled. In 2013 those who make the rules decreed that electric bike riders in Australia should be like the europeans. And so allowable power is increased to a big 250 watts and throttles are not allowed…unless the bike complies with the old 200 watt rule.

That is unfortunate. I’ve found that all the customers would prefer to have a throttle.

So, if we are limited to 250 watts, how much is that? If you get on one of those machines at a gym that tell you how hard you are working out you would find 250 watts is a good workout – for most people. It is about what a fit person can sustain. Tour de France guys can do twice that, but that is not you or I. On a flat road 250 watts will take you to about 25 kmh with minimal effort on your part. And at 25 kmh the motor is supposed to cut out. (Speed uphill is another topic).

E-BIKE MOTOR Front, Back, or Mid?

Where best your e-bike motor – front wheel, rear wheel, or in between?

Until now the majority of production electric bikes have had a hub motor in the rear wheel. The more powerful (ie “offroad”) will stay with rear wheel drive, either hub motor or chain motor, because they need all the traction they can get, and there is more weight on the rear wheel.

For bike conversions you can choose either front wheel or rear wheel drive. Several factors influence your choice.

If you ride tracks a rear wheel drive is better because even the lower power 250 watt bikes with front wheel drive lose traction on sandy or loose tracks.

If you have “cassette” gears and not a screw on gearset and you’d prefer to keep those then you (may) need a front wheel motor, because rear wheel motors mostly have provision for screw on gears. There are only few motors for cassette gears, and they are more expensive.

If you are likely to be swapping your powered wheel and original wheel then it’s easier to do that with the front wheel.

Mid mounted motors for conversions are possible and there are some kits for that. These have used a motor attached by a bracket to the bike and driving the chain with a small sprocket. That arrangement is more difficult to install.  Motors that integrate the chainwheel and cranks that fit into the bottom bracket (where pedal axle is) are now available and they are easier to install.

The difference between front wheel and rear wheel drive for a bicycle is much the same as it is for a car.  It’s a personal choice.

There’s a trend away from rear motor towards front wheel hub motors or mid mount chain driving motors in production bikes. 

The hub motors for a front wheel are very similar to the ones for a rear wheel. They need to fit into a 100mm space between the forks instead of 135mm for a rear fork. Usually a motor is designed to fit either front or rear so the only noticeable difference is that the front motor is missing the lug which gears attach to and has a shorter axle. There is very little cost or weight difference.

More brands of electric bikes are now being produced with a motor between the pedals or adjacent to the pedals. This is achieved 3 ways.

  • Integrated pedal, chainwheel and motor in specially designed frame. The motors are made by Panasonic or Bosch. They are welded to the bike frame and they completely replace the bottom bracket. The systems are expensive, and so are the bikes that incorporate them, but are becoming common in Europe with many brands having a mid drive motor, especially Bosch. The Europeans are much more accustomed to paying a high price for a bicycle and they do expect quality parts.
  • A separate motor attaching to chainwheel or pedal axle. Some bikes from China have these systems. They are much cheaper – similar in price to the hub motor bikes from China.
  • A motor incorporated into the bottom bracket inside right pedal crank.These are made by Bafang in China (a motor of good repute)These can be fitted into bottom bracket of (most?) bikes replacing chainwheel and pedals and so can convert (most?) ordinary bikes to e-bikes. I see one big e-bike brand in US will be selling bikes with these motors. The cost for this system is a little more than the systems with separate motor and much less than the Bosch or Panasonic systems. I expect they will be more reliable and simpler to operate than the cheaper systems with separate motors

You can read about the pros and cons for these mid drive systems elsewhere.

What kinds of motor in e-bikes?

What kinds of motors does an e-bike have?

The short answer is BLDC where BL means “brushless” and DC means “direct current”.

Direct current means that the current always goes in one direction, that is from positive (red) to negative (black) as opposed alternating current (AC), as in household supply, where the current reverses direction 60 times per second. DC motors can use power from a battery or AC to DC transformer.

To make an electric motor turn the current has to go to different segments of the ring of wire coils inside the motor. Until recently most DC motors had a “brush” to do the switching. The brush is in contact with a metal ring with 2 segments and so the brush switches current to two halves of the coil every revolution of the motor. Anyone with an old power tool or car starter motor may know the brushes wear out.

Brushless means without brush, of course, and brushless motors are different inside. There are many more segments of the coils and they are wired as groups of three. Power is sent to the groups in turn by an electronic switch within what is called a “controller”. That is usually a separate metal box. The current going to the motor coils needs to be “in sync” with the motor and for that there is feedback from 3 sensors within the motor to the controller. These are called Hall sensors. The controller has other functions than to send power to the motor coils. It interprets signals from the throttle or pedal assist system (PAS). Some controllers also send signals to (and get signals from) a control panel – for instance, motor speed (hence bike speed) and the level of assistance.

In Asia many of the cheaper electric bikes have brushed motor. Some older electric bikes here may have a brushed DC motor.

There are two types of BLDC motors powering electric bikes. Ungeared (or direct drive) and geared. The difference being having gears (usually internal) or not having gears.

The ungeared motors are larger diameter (usually about 250 to 350mm and pancake shaped). The larger diameter enables the motor to have more power and rotate slower. The motor rotor is fixed to the axle and its speed IS the wheel speed and there are no other moving parts inside other than the rotor. Hub motors more than about 350 watts are usually ungeared motors.

The geared motors have smaller diameter and spin much faster. Because the motor spins 5 to 10, or more, times faster than the wheel (or the equivalent for motors driving the chain) there needs to be a gear system to reduce the speed of the power output shaft. Most geared motors will have internal gears. Some of the motors driving the chain or pedal axle will have external gears outside the actual motor case.

You may see mention of “torque”. Sometimes that is confusing, and meant to exaggerate the claimed power of the bike. It is irelevant. A large ungeared slow revving motor may have 10 times the torque of a small geared fast revving motor, yet both having same power output. That is because power = torque X motor speed. That is 10 times the torque with one tenth of the speed is the same power.

In nearly all cases a bike that’s legal in Australia will have a small geared motor. Either in hub of front or rear wheel, or centrally located near the pedals. (That’s a separate question). There are few ungeared hubmotors with 200 or 250 watts.

AUSTRALIAN E-BIKE LAWS

What’s a legal e-bike and what’s not?

What is legal for an electric bicycle in Australia has changed. Not a lot. Just a little. Electric bikes now have to comply with European Standard EN15194 You can read it. (pdf file)

Changes to the Law

  • Pedalling is now necessary (A standing start from 0 to 6kmh without need of pedalling is allowed).
  • Assistance to rider (by PAS) must reduce as speed increases up to 25 kmh and cease beyond 25kmh.
  • The motor must stop within 2 metres of your stopping pedalling.
  • Allowable power is increased to 250 Watts, with these provisos.

It follows from that that the e-bike cannot go faster than 6kph with only its own power, and cannot assist you to go faster than 25kmh…
Although there is no limit to your speed with your own unassisted pedalling.

The previous rule required “not capable of more than 200 watts”
The new rule allows “continuous rated power output of 250 watts”…
but “peak power” can be higher, and
there is allowance of 15% for transmission losses between motor shaft output (if power output is measured there), otherwise it is “on the road” power that counts),
and there is a 5% tolerance in test results.
This effectively means that a motor rated as 300 watt input might comply.

Other Changes to the Law

There are very many other provisions in EN 15194 covering

  • The Battery and the electric system – including cables, sockets and connections.
  • The frame – construction standards, strength
  • Safety – braking performance
  • Testing – of all the above.

Note that changes will affect bikes imported in future and that electric bicycles that are already here that comply with the old rules can be used and sold.

Any e-bike not complying with EN 15194 is limited to 200 watts, and may have a throttle usable at any speed. That would be most e-bikes imported under the previous rules.

There may be different interpretations of the rule. “Bicycle” is not well defined, and neither is “assistance”, “capable of” and even ” a road”, and whether adjacent footpaths or bikeways are part of it. Unusual shaped bikes and ineffective pedals could be challenged as not being a “bicycle”.

Many Parks and forests have “no motorbikes” signs but don’t specify electric bikes.

The rules declare that a bicycle with any fuelled motor is a moped and must be registered as such, although that is not likely to be possible in practice.

In other countries the rules, or lack of rules, varies.
In US the legal limit is 750 watts and seems to be not enforced.
In most of Europe the philosophy has been that riders should be pedalling but may be assisted, but they should not be going faster than 25kmh anyway, and so they should not be helped to go faster than 25 kmh. That is fine for compact, dense, slow moving and generally flat cities like Amsterdam, London, Paris and Berlin but not so for more hilly, spread out, faster moving cities like Sydney or Brisbane. In adopting the European Law Australian governments adopted the European thinking.

In Asia there the cities are so congested that limits would have no effect.

In Switzerland and Canada they have a more reasonable compromise –  500 watts but with 25kmh speed limit. Maybe if enough bike riders say something to their politicians Australia may have that too.