How Far can you Go on an electric bike?
Rider, Motor & Battery
There are many factors which affect the range of an electric bike.
On the one hand there are the physical features of the rider, how the bike is ridden and the weight and fitness of the rider
On the other are the wattage of the motor, capacity of the battery and to a certain extent the equipment and condition of the bike
Clearly, a fit light rider on a flat road with a following wind is going to do better than an unfit rider on a hilly terrain with a strong headwind. You will need to decide where you fit on this continuum. What sort of riding over what type of terrain are you going to use your electric bike?
Legal and other limitations
The motor and capacity of the battery set the limits.
In the UK and EU the maximum wattage for an electric bike, to remain legal on the road, is 250W and may be designed to run at various voltages. The most common are 36V & 48V. 250W is the rating of the motor under continuous load. For short periods a 250W motor may be able to assist by delivering up to double that power. In those short periods, the motor will take more out of the battery.
Batteries are much more variable. The voltage (V) must match the motor, but it can be a range of Ampere (Ah) sizes. V X Ah = Wh. Using this formula, a 36V X 10Ah battery will deliver 360Wh of energy. Or, a 48V X 16Ah batter will delivery768Wh – over double the 36V X 10Ah. The capacity of the battery is reflected in the price.
If you have a 360Wh battery and a 250W motor, in theory the battery will run the motor 360/250 = 1.44 hours. But nothing is 100% efficient, and an electric bike electrical system might well be 85% efficient. 1.44 X 85% = 1.22Hrs. Let’s say 1.25hours – 75 minutes
This means that if you ride the bike over a flat ground and use only throttle and no rider effort, in this case the bike will run for 1.25 hours at (say) 12mph. This will give a range of 15 miles.
Increasing and Reducing the Range
The range is increased by rider effort, using the bike’s gears, not riding the bike on maximum power or Turbo. additionally the range is also increased by road tyres correctly inflated. (MTB tyres increase the rolling resistance of the bike so reducing range.) A well serviced and lubricated bike will always perform better.
On the other hand, the range is decreased by steep hills causing the motor to run beyond its rated capacity, (although no power will be used freewheeling on the downhill sections). A heavy unfit rider, strong headwind, using full power, using high gears on the bike when a lower gear would be beneficial.
Under inflated tyres are the most common reason for poor performance on an electric bike.
Conclusion
As a rule of thumb, and a happy medium, the following ideas are helpful.
Say a reasonably fit rider, provides 50% of the power himself. On a medium power setting, can expect to achieve 3 miles per battery Ah. This means that a 36V X 10 Ah battery will last around 30 miles. A 48V X 16Ah battery might be expected to give assistance for 60 -65 miles.
Many riders setting off on a long ride choose Eco Power. Others even switch OFF on easy parts of the ride, so extending the range. Otherwise, a commuter who knows how far he has to travel may choose, Turbo. He pedals lightly so arriving at work as soon as possible with the least exertion.
The choice is yours at the flick of a switch
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