E-Bikes - What You Need To Know
Electric-assisted bikes are becoming more popular and it can be confusing as to why models are so different in price. There are four things to consider when you buy an E-bike -
BATTERY - MOTOR - BIKE - WARRANTY
The Giant and Trek E-Bikes that we stock use lithium ion batteries for their light weight relative to physical size and electrical capacity. Electrical capacity causes a lot of confusion for customers, with different numbers being quoted by different sellers. The battery costs about a third of the total bike cost, so getting the right battery size is important for your usage. This section gives you the lowdown on battery numbers and what they mean.
Voltage - as far as E-bikes are concerned, higher voltages are better, and the standard that has been adopted among major manufacturers is 36V (up from the earlier 24V and 26V bikes). Voltage is a measure of how high the energy level is. If you can make a battery of the same size and weight run at 36V instead of 24V, you can store 50% more energy in it. Its a bit like a tank of water at 36 metres high instead of 24 metres - its the same amount of water in the same tank but its harder to pump it up there and it comes down much faster! As with water, the higher voltage, the more problems you have controlling the pressure, so 36 Volts is chosen as a practical compromise.
Amp hours - this figure tells you how much current can be released from the battery in an hour. A 10 Amp hour battery can run at the full 10 Amps for an hour. With the tank of water example, a big pipe lets a lot of water out, while a small one doesn't, even though the water is still up there at the same height. The size of the pipe sets the current flow from the tank while with the battery the size and design of the cables and battery internals sets the maximum current flow.
Watts - this is the power of the battery and this equals the Voltage multiplied by the Amp hour rating. With the tank of water, its the amount of power you can generate with a turbine in the water flow - let lots of water out and it will be more powerful but for less time. For a 10 Ah pack rated at 36V, you get 360 Watt hours - you should be able to get 360 Watts of power for one hour. However - UK E-bikes are limited to 250 Watts max output at any one time, so the power output will be "throttled back" to 250 Watts (like a foot on the pipe!), which would mean that you get the other 110 Watts to use in the next hour. If you kept using the power at 250 Watts per hour, you would get about 20 minutes more.
What does all this mean for cycling? Consider that a racing cyclist generates over 400 Watts continuous when pushing hard. Remember that your E-bike stops assisting at 15mph (that's the law). A touring cyclist can ride all day at about 90 Watts, which can be done because they go much slower than the racer, averaging 12-15mph. Most of their energy goes to beat wind resistance and climb hills. If your bike has 360 Watt hours available, how you use it affects "how far" you can go. If you ride steady, minimising wind resistance, with an eco setting on the controller, you will use less than 10 Watt hours per mile (say a 45% boost to your own 22 Watt input), so you can go at least 36 miles. If you ride just under 15 mph and use 20 Watts hours per mile, you will get 18 miles. Throw in some steep hills and keep your pace up and your mileage can come down to 10 miles! NOTE - THESE NUMBERS ARE TRUE IN THE REAL WORLD. Do not believe those who claim their e-bike will do 100 miles on one charge!! Physics does not lie - their bike probably could do 100 miles, but only on dead flat roads with no wind and at a constant speed. Of course, you could ride over 15 mph and not use the battery at all.... but then maybe you should just consider buying an ordinary bike!!
Giant's ENERGYPAK batteries are either 300, 400 or 500 watt hours depending on the model
Trek's Conduit+, Dual Sport+, Neko+ use the Shimano Steps 6000 series battery rated at 418 watt hours
Trek's Super Commuter and Powerfly Series use the Bosch 500 watt hours battery
How Much Boost From The Battery?
Pedal assist bikes have three or more settings to adjust the amount of boost you get. With Giant crank motors, you get
Eco - adds 45% more - you provide 30 watts, the bike provides 13.5 watts
Standard - adds 90% more - your provide 30 watts, the bike provides 27 watts
Sport - adds 300% more - you provide 30 watts, the bike provides 90 watts. Note that on the flat it won't because you will be going over 15mph!
There are two types of motor utilised by E-Bikes, Hub drive or Crank drive. Crank drive is deemed the most efficient and its position in the middle of the bike at a low point gives a good balanced feel whilst riding. Hub drive is a cheaper option and ideal for lower torque bikes.
All motors are limited to a maximum 250 watts of power for use on the roads in the UK, so their maximum power output rating is not useful to the rider. They do vary in the amount of torque they provide, and this has a significant effect on the cost of the motor system. Torque can best be described as how fast the motor gets to maximum assistance and higher torque motors tend to have more complex windings to get the power into rotation faster (with the water tank example, you would use a wider diameter turbine to get the shaft up to speed faster). For off road riding and larger hills more torque is better. Be aware though that higher torque uses more power - if you want to commute and are more interested in distance, a lower torque motor would be better, because the higher power is used every time you accelerate away from the lights. There are lots of motor manufacturers but Yamaha, Bosch and Shimano are recognised leaders in light, efficient, high torque motors.
Motor torque ratings for bikes we supply are -
Giant Prime-E+ series, crank drive models Giant Syncdrive (Yamaha Motor) 60 Nm torque
Giant Quick, Road and Dirt E+ series, crank drive models Giant Syncdrive (Yamaha Motor) 80 Nm torque
Giant front wheel hub drive Ease-E+ model Giant Syncdrive motor 30 Nm Torque
Trek Conduit+, Dual Sport+, Neko+ Shimano E6000 Series Steps Motor 50 Nm torque
Trek Super Commuter Series Bosch Performance Line Cx Motor 75 Nm torque
Trek Powerfly Series Bosch Performance Line Cx 75 Nm torque
A lot of interest is focused on the electric bits of an E-bike but they are all still attached to a bike and the style and quality of the bike influences the cost. As with all bikes, if you want lighter it costs more and if you want more functions, it costs more. The Giant Ease-E+ commuter at £1249 is our "entry level" bike. It performs well as a commuter and lanes rider, carries luggage at the back and has a comfortable upright riding position. The Prime-E+ 3 bikes have both more powerful battery packs and higher torque motors with a different frame and suspension front fork. These improvements move the cost up to £2099. The Prime-E+ 2 has 10 speed gearing, better brakes plus a bigger battery pack, and it costs £2499. Similarly the Road-E+ and mountain bikes offer additional lightness and performance as bikes and have the 80Nm torque motor, which all contribute to the overall cost.
Warranty and Service
With a complicated electric package on your E-bike you want to know that you can get problems fixed. Our mechanics are trained and experienced in maintaining our existing customers' e-bikes over many years. In addition, both Giant and Trek offer full after market support and comprehensive warranties. The table below is a brief comparison of warranties offered by Trek and Giant - for full details of cover please refer to each manufacturer's website.
Frame Lifetime Original Owner Lifetime Original Owner
Rigid Fork 10 years 2 Years
Frames on models intended for downhill purpose 3 years 3 Years
Batteries and electric HPB components 2 years 2 Years (or 600 charges, whichever comes first)
Paint finish and decals. 1 year 1 Year