I want to buy an e-bike - a few things to consider

 

Peter and Margaret are keen to purchase e-bikes, well, they think they are keen, but not really sure. There are so many on the market and it’s all a bit confusing. This small article  will help you understand what to consider when buying an e-bike. We have added a small summary at the end.

Am I cheating by riding an e-bike ?

Do we cheat by driving cars to get between A & B? Are we cheating by wearing shoes?

Fishman and Cherry two researchers did a comprehensive review on e-bikes including health benefits. They found “ the clear theme emerging from research on e-bikes and physical activity is that they provide a lower level of physical activity than traditional bikes, but still achieve a level necessary for health enhancement. The black and white of this is most e-bikes don’t work unless you pedal, “ No pedal no power, no assistance”. You may have a lower heart rate than unpowered cyclist, but not significantly less. You are not cheating, you are out there getting fresh air and exercise.

There are different drive systems, lets call it style of e-bikes

Pedelecs is a word blend of “pedal” and “electric” or as the Aussies say “Pedalec, Kiwi’s say “pedal assist” This describes an electric power assisted cycle where a motor of up to 250 Watts engages if the cyclist pedals and progressively reduces assistance before ceasing at the motor cut off of either 25 km/h (European standard) or 32 km/h ( American standard)

To get to the nitty gritty, components of an e-bike are the BATTERY , MOTOR, MOTOR CONTROLLER and a PEDAL ASSIST SENSOR (PAS) and a HANDLE BAR MOUNTED CONSOLE WITH POWER LEVEL CONTROLS. Motors may be located in the front wheel hub, rear wheel hub or at the pedal crank, what we term “Mid Drive”.

Batteries maybe located on the top tube, seat tube, rear carrier.

How does Pedal Assist ( PAS) work ?

There are two types of Pedal Assist – Magnetic and Torque

Magnetic motion sensors detect pedal crank motion (cadence) or wheel rotation, irrespective of the amount of human effort.

While they are generally inexpensive, a major disadvantage is that when motion is detected, the motor will activate up to the maximum motor torque or vehicle speed parameters set by the user via the console and limited by controller software settings.

 This can result in a “Jerky” or “non-linear and unintended level of acceleration or speed, and a common complaint is the power transmission feels ‘jerky’.

This characteristic can cause loss of control, especially for front wheel drives and when used off-road, and therefore riders tend to prefer throttle operation.

To the point, less human effort is required to accelerate or maintain a given speed with a magnetic sensor than with a torque sensor.

 Torque sensors detect human power input and the motor torque is applied proportionally. This provides a seamless and smooth power delivery, in proportion to the amount of human effort.

Users typically describe the feeling of riding a torque sensor equipped bike as just like an unpowered bike, but the rider feels ‘bionic’. Torque sensors are standard on costlier European models, but the price differential has been reducing lately.

Torque sensors used in mid-drive systems are integrated into the motor and crank mechanism.

In a nutshell, a magnetic sensor detects how fast the user is pedaling (or that there is pedaling motion), while a torque sensor detects how hard the user is pedaling.

Some high-end e-bikes have both sensor types, enabling the user to select motion-sensing mode for on-road use and torque sensing mode for off-road use using buttons on the handlebar console.

Throttle Controls

E-bikes with a throttle (also known as an ‘auxiliary’ or ‘over-ride’ throttle) can provide motor assistance when the user pedals or when the throttle is operated. Therefore, the user does not need to pedal at all.

Throttles can be in the form of a button or ‘twist and go’ grip, the latter in particular are common in New Zealand because of perceived or actual advantages for people with disabilities, hills, and/or higher speeds.

Interesting to note most European Pedelecs and almost all mid drive (pedal crank) e-bikes powered by motors such as Shimano STEPs, Bosch and Yamaha do not have throttles.

Lower priced e-bikes usually have a twist grip throttle and a magnetic motion pedal assist.

Batteries.

The e-bike battery is the fuel tank, simply the bigger capacity battery your bike means  you can go further. When purchasing an e-bike ensure the battery that comes with the e-bike will get you to where you want to go. In other words if you compare two e-bikes with similar drive systems the bigger battery will go further. Be aware this can be misleading, this distance you travel on an e-bike is determined by the weight of the rider, the terrain you cycle on ( hills or flat ) and the power setting you use. If you cycle on hilly terrain on full power ( High or turbo setting)

Most e-bike batteries are lithium-ion they weigh about 2.3kgs ( e-bike motors weigh a similar amount)

The capacity of a battery is determined by Watt Hours a 36V X 11 amps equals 396 Watt Hours ( the marketing people refer to this as 400 Watt Hours)

This battery connected to a mid drive motor with a torque sensor system should get you in distance between 80 and 120 km. ( We highly recommend you read the bike specs before buying a e-bike.

Batteries are not cheap a 400 Watt Hour Bosch battery retails for about $NZ1000.

What is the life of the bikes battery.

E-bike batteries are rechargeable, most lithium-ion batteries are able to recharged ( from flat to full charge ) 500 times. After this the battery gradually loses its capacity. It should maintain 60 to 70% capacity.

In a  test carried out in autumn ( Germany) 2015 a Bosch e-bike battery was fully discharged and recharged 1,515 times before it retained only 30% of its original capacity and was no longer of any real use. This means that the battery would have been sufficient for up to 57,000 km’s – or one and a half times round the globe.

You are still a little confused about e-bikes.A quick summary of what to look for when buying an e-bike

1.Test ride the bike you are keen on, not a 2 minute ride around a car park, go for at least an hour or take the bike overnight. Is the frame the right size, is the seat comfy. Can you lift the bike, just in case you need to put the bike on a car bike rack. Most e-bikes are between 23 – 26kgs

2.Check the battery capacity, is this sufficient for your needs. How long will the battery last?

3. Check the components of the e-bike are of good quality, often cheaper e-bikes have lower quality components ( pedals, brakes, derailleurs  etc)

4.Do you need a Pedelec or a throttle power system. Do you want the motor cut out to be 25km/h or 32km/h. How much power are you really comfortable with. Remember most e-bikes have a motor cut out system, European is – 25 km/h and the Americanis 32 km/h. Why, is all about safety. If you want to cycle faster you need to pedal with human power.

5. Do you want a hub drive ( front or rear wheel) or a mid-drive. Test them both.

6. Can the motors be serviced in New Zealand? Ask your retailer.

(Bosch and Shimano STEPS are both serviced in NZ).

7. Remember e-bikes are wonderful, they get you places with less effort, it cost about 12 cents to fully charge a battery.

8. Go on give it a go.

9. A big bonus. If you are a member of the NZ Automobile Association note they look after e-bikes with breakdowns.

 

 

 

 

4I6A1376.jpg
Brian Fisher