Wednesday, March 9, 2016

Rethinking transport

What got me thinking about transport (yet again) was an Australian-sold electric scooter, the Fonzarelli. They look very cool, cost AU$5000 and don't require a motorbike license. Because they're small, registration is much cheaper, and the electricity-use would be small. It looks very attractive, and I'd quite like to ride one -- compared with a car, it is an extremely economical way to get around.

Then I started comparing the electric scooter to a bike or ebike, and there are several disadvantages:
  • It's relatively expensive
  • it needs to be registered (annual fee)
  • it's not modular (I'll come to this)
  • It can't be ridden on bicycle paths (it's confined to roads)
  • It can carry one pillion passenger only (in addition to the driver)
One advantage is a top speed of 75 km/h means it can be ridden comfortably on major roads (if the user has a license that allows this -- otherwise it can be programmed to limit the speed to 50 km/h). Let's quickly go through these dot points:


A new ebike can be bought from $1500, although good ones are more like $2500. A retrofit kit can be bought from about $800 to fit to an existing bike.


Modularity means that a bicycle can be built from easy-to-assemble off-the-shelf components that can be chosen depending on your requirements.
If the DIY path is chosen, you can build a customised bicycle that is specific to your requirements, and can build it from off-the-shelf parts. Want to carry three children? A surfboard? Tradie's tools? A piano? All these things can be carried on a bicycle (and possibly all at once, if you're keen). The other benefit of modularity is that if any component fails, it is easily replaced by the user (instead of needing to send the whole vehicle in for repair) -- this is both cheaper and more convenient. If you are a bit handy, I recommend the modular, DIY approach.

Bicycle-path access

Australian cities have shared-off-road paths that are for use by pedestrians and cyclists only. To cycle on these paths legally, you must ride a "bicycle" -- there is a definition for this. An electric scooter does not count -- scooters must remain on the road. To my mind, one of the great benefits of cycling is the flexibility to leave the road and ride on off-road tracks and (in some states) the footpath [1]. Even in the centre of the city, these are often through paths which take you away from traffic congestion and red-lights.

What is a "bicycle"?

In Australia, there are laws about adding electric motors to bikes. Essentially, there are two options:
  1. you are limited to a 200 W motor, and it can be operated by a throttle (like a motorbike) if you want (I have a throttle on my bike -- it's easier to install than a pedal sensor)
  2. 250 W motor, but pedal assist only, and the motor cuts out at 25 km/h


In the days when motor vehicle (even motor bike) engines routinely output 15 - 100 kW, you may think why bother with 250W?? It is such a comparatively-small amount of power -- what does it do? Does it do anything?

An average fit adult can sustain an output cycling power of about 200 W. The motor will double that. This makes cycling up big hills, or with lots of luggage, feasible for only moderately-fit cyclists. My ebike motor can accelerate me to its maximum speed (25km/h) on the flat without pedaling. Generally, it makes hills feel flat, and the flat feel like a strong tail-wind.
25 km/h doesn't sound fast, but it is (qualitatively) above the average speed of cars in the city (in terms of getting from source to destination), it is also faster than the tram, though not as fast as the train though.

An example of an ebike trip

I took the kids bushwalking in the Adelaide hills. We caught the train to Blackwood, then cycled up the hill through the Belair National Park, out the back of the park, and on to the Mark Oliphant Conservation Park. Although I do have the fitness to pull the kids up there without motor assistance, it would not have been feasible that day (also it would be much slower, which would try their patience).

This is the route we took. I should add that, although google estimates this route to take 2h:40m to ride, it took us under 2 h (to drive would have taken about 35 mins each way, assuming no traffic congestion). Typically, our car uses about 25 L/100km when going up a hill. I think we would have used at least 10L of petrol had we driven there and back -- 10L of petrol contains energy equivalent to about 100 kWh, and would cost about $10 (at current low oil prices). Conversely, the electricity to charge the ebike is worth about $0.24, and the battery depreciation through use was about $2 (battery cost $500, about 500 cycles before replacement)

Monetary Savings

I think it's interesting that even with
  1. the sunk cost of car registration and insurance
  2. the very low price of petrol
there is still a considerable saving of cycling the ebike versus driving the car. It was nicer too -- we got to cycle through the national park, which we couldn't have done in the car.

Energy Savings

To manufacture a 1 kWh lithium ion battery uses about 500 kWh of energy. Assuming a lifetime of 500 discharges, this implies a manufacturing cost, per battery charge cycle, of 1 kWh. If I fully drained the battery on our cycle to the park, then there would be an additional charging "cost" of 1 kWh. That means the trip with my kids "cost" 2 kWh on the ebike.
Compare that to the fuel cost estimate in the car of 100 kWh (which does not include manufacturing or maintenance of the car or road), and we can conclude that the ebike uses less than 1/50th the energy of the car. This is such a big saving that I conclude, unequivocally, that ebikes are a Good Thing if their use displaces car use.

[1] I regularly cycle on the footpath, and it is legal to do so in South Australia. I think it is very important that cyclists are careful and courteous on the footpath. Please remember that there will be very young, very old, mobility-impaired and sensory-impaired people on the footpath and cycle accordingly. Remember, too, that sightlines on the footpath are not as good as on the road -- you will regularly find blind corners. I would never cycle above about 10 km/h on the footpath, and would go past a pedestrian at walking pace.


  1. Hi Angus,

    I had no idea about the lithium batteries. Yikes!

    Hey, out of curiosity, do you know of any 12V or 24V electric motors that pack a bit of grunt? I was thinking of constructing an electric trolley that will assist me with pulling heavy rocks back up the hill (only a short distance, but they're heavy)?



  2. Hi Chris,

    I presume you mean the cost of manufacture of lithium batteries? Yes, it is high, and should really be factored as an efficiency loss of the system. The efficiency of the motor is very high though, so that does help to even things out.

    I think you could do it, with a simple induction motor. Possibly you could salvage a motor from a washing machine or something? I'm not sure it is the best way to do what you want to do though -- have you considered using a winch to drag it up the hill? If you had a winch (electric, or even pedal powered) higher up the hill, then you could couple it to a wheel-barrow or similar. Whether that would work for you depends on lots of things -- like whether you had help to move the cart, the terrain, distance, etc. If you went electric, you could probably remote-control the winch, so you could then handle the barrow and control the winch at the same time...

    Pedal powered winches can be extremely powerful -- I know a guy who made a plough that was powered by a pedal powered winch.

    Cheers, Angus

  3. Hi Angus,

    You've got my brain working and I've spotted that 24V motors are available up to 500W for very little cost. Now your ebike is 250W and I was wondering about the performance of that motor on a hill? Does it have enough grunt to push your weight + the bike up the hill?

    I'm sort of imagining a very low slung pallet trolley with an electric motor. I haven't figured out all the details yet, but will get there - eventually.

    48V motors can provide up to 1,000W of grunt. Do you believe they would be a better option?

    I'd really appreciate your thoughts in this matter if you have the time to spare me? I'm looking to walk behind the trolley and more or less guide it back up the hill.



  4. Hi Chris,

    With my pedaling, the ebike can pull myself, the kids and luggage (maybe 150kg, inc the bike) up a 20% gradient.

    An important consideration though is that, the slower we ride, the more my pedaling contributes relative to the motor. Conversely, because it isn't geared, it loses mechanical advantage at low speeds ;-)

    For you, I think the important considerations are:
    1. How fast do you want it to go (I'm guessing walking pace)
    2. How steep and uneven is the surface
    3. How heavy will it be
    4. Can you help it (by pushing)

    If you use gearing to help the motor (instead of using hub motors), then even a 100 W motor can push up the hill, given a sufficiently low gearing. But yes, if you want hub motors, then they have a fixed gearing.
    If you're going for a four wheel cart, I would consider using two hub motors - one on each rear wheel (going uphill). I'm not convinced you'd need 1000W motors, and think that 2 x 250W would be plenty of power. But of course, if you want to take 500 kg of cargo, that changes things (I'm not sure that would be feasible with bike wheels anyway)

    Happy to provide what help I can ;-)

    Cheers, Angus


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