How do electric bikes work? We are going to take a look at the answer to this question and demystify electric bikes and answer all the questions you may have if you are considering an electric bike. In this article, we first look at what an e bike is followed by a look at electric bike specific components such as the motor, battery and sensors. We then go on to explore how to use an electric bike and some charging tips and battery care. We then round it all off with a look at the other components such as gearing and brakes.
Contents and Quick Links
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What is an E Bike - a look at what makes an e bike an e bike?
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E Bike Components - a look at the motor, battery and sensors
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How to use an e bike - a run down of how to use an e bike
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Charging and battery care - some simple tips to get the most out of your battery and motor
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Other components - a look at brakes and gearing
What is an Ebike?
An ebike is a bicycle with added electric motor system and battery to give assistance when required. All electric bikes work by assisting when you are pedalling by either supplying power through the bottom bracket (mid drive motor) or through a motor on the front or rear wheel hubs. If you are not pedalling, there is no assistance. Electric bikes in the UK are limited to 25kph (15.5mph) assisted but are capable of going faster however it will have to be powered wholly by you or by gravity going downhill.
The benefits of electric bikes are numerous but amongst them are:-
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The ability to commute and arrive at work without being sweaty
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Electric bikes remove any barriers to getting in to cycling by requiring less fitness at the outset
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More confidence cycling in cities by being able to start up quicker from traffic lights or from a stationary start
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They make replacing car journeys much more possible
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Cheaper to run and better than the environment than cars
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Great for your overall health
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Low impact on joints
E Bike Components
As mentioned above, the key components of an electric bike are the motor, the battery and the sensor. We will take a look at each of these in turn and detail some of the differences that these make to the overall riding experience.
The Motor
The motor on the electric bike is responsible for the power supplied when the motor is engaged. The motor assistance is measured in Nm (Newton Metres) and dictates how much torque is supplied. Essentially, the higher the number, the more power you will get particularly uphill or when carrying a lot of luggage. When we are discussing the best motor system for you, we would ask what type of riding, how many hills you expect to do and how much luggage you expect to be carrying before recommending a system.
Electric bike Motor power is measured in n/m (Newton/Metres) and the higher the number, the more torque the motor offers and the easier the bike will power you up hills. Electric bike laws in the UK dictate the maximum speed you can be assisted to is 15.5mph or 25kmph and all electric bikes sold in the UK, to abide by UK law, will be a pedal assist bike.
On modern electric bikes, you have 3 different positions that the electric bike motors can go – Front hub, rear hub and centre driven motors and each motor system will give a different feel and affect how much power the motor delivers. The pro's of each will be discussed below.
Front Hub
Front driven hubs are relatively inexpensive (the exception is the Brompton Electric Bike price which is a touch higher but this is due to the engineering and folding mechanism of the bike itself) and give you a good amount of power up hills. Good for tarmac rides on a budget and the initial acceleration is sufficient to get you away from lights or from a standing start which makes these perfect for city cycling on tarmac.
Where we would not recommend this style of motor system is on loose surfaces as the assistance relies on traction from the front wheel and tyre so when the surface is loose, you can have some slippage which affects the handling an performance.
We have Brompton Shops in Edinburgh (Canonmills and Bruntsfield), Leeds and Aberdeen.
Rear Hub
Rear hub driven motors are also relatively inexpensive, give good acceleration and are more for flat tarmac rides as there is a lot of weight towards the rear of the bike. The new Rheo 2 & 3 Whyte E Bikes are a great example of a rear hub driven motor.
One aspect to note about these systems is that it can be a little more complicated to remove the rear wheel so some learning is required or upgrade to some puncture resistant tyres to avoid the need to change the tube.
Centre driven
Most e-bikes over a certain price come with a centre driven electric motor, or mid drive motor, as this provides the most natural feel, a better balanced bike (weight towards the centre of the bike) and a higher power output, increasing how much assistance is provided on steep hills. They are also the more reliable e bike motors systems. The amount of power provided will depend on the motor type such as Bosch performance line, Bosch active line or the Shimano Steps systems.
On of the main benefits of these systems is the use of a torque sensor that can give assistance dependant on how hard you push on the pedals and there are certain assist modes that can give more or less power that reacts to your input. The "Auto" mode in the Bosch smart system and Giant bicycles have an automatic mode that avoids the need to keep flipping between modes of assistance.
Battery
Battery power is measured in w/h (watt/hours) and is an indicator of the range of the electric bike with approximately 100w/h equating to 10 miles of range. This, of course, is an approximation and very much depends on how you use the bike, how many hills you take in and how much weight you carry.
For some of the lighter weight electric bikes, you sacrifice the battery capacity for a lighter bike so a battery capacity of around 320Wh is normal as on these bikes, you will rely less on the motor and battery and only require the assistance on the steeper hills or in stronger winds.
One of the factors of electric bike performance and handling is to do with the battery position on the bicycle. This is worth a discussion as this can vastly affect how the bike handles so we will have a look at the options here. The main positions are: above the rear wheel, on the bike's downtube or integrated into the bike's downtube.
Rack mounted
Commonly found on lower budget e-bikes as the main body of the frame doesn't need to be reinforced to facilitate the battery. The weight distribution on these bikes is further back and higher. Electric bikes with a rear rack mounted battery are great for leisurely rides on fairly flat terrain.
On the downtube
Similar to a centre driven motor, the downtube mounted battery moves the weight to the centre and makes for a more balanced bike which is noticeable when cornering and/or travelling uphill.
Integrated
Aside from being more balanced due to the centre of gravity, an integrated battery moves the weight lower on the bike to aid handling and climbing and a lot of people prefer the looks of an interated battery. Most integrated batteries can still be removed from the frame for charging indoors. You will normally find these type of batteries on electric mountain bikes (e MTB) as there is a premium of responsive handling when you are flying downhill.
The Sensor
The type of torque sensor used on ebikes has a massive effect on the ride quality and how natural the bicycle feels. A speed sensor will generally be found on front or rear hub motors and this type of sensor will engage as soon as you start pedalling and will give the same output regardless of how hard you push the pedals.
A torque sensor is the more advanced sensor as this will gauge how hard you are pushing the pedals and give output dependant on this. This makes for a much more natural feel and a more progressive power engagement.
How to use an ebike
Using an ebike is one of those activities that seems complicated but is actually incredibly simple. An ebike is exactly the same as a non ebike aside from the fact you control the assistance required through buttons by the left hand (there are a few exceptions to this such as the Brompton electric which is controlled from the top of the battery). Once you have chosen your assistance mode, you simply start pedalling and enjoy the assistance. as you are cycling, you can adjust the mode depending whether you are going uphill, downhill or on the flat.
Managing this will help preserve your battery life and make it last for long rides and you then just use the gears and brakes as normal.
One huge note to remember for making your battery last longer is to keep your cadence (the speed your legs rotate) higher as this puts less pressure on the motor and therefore, the battery. A cadence of above 80 is ideal but just bear in mind; the lower the cadence, the less the range the battery will give.
Charging and battery care
Modern batteries from reputable companies will have been checked to the highest standards so offer a high level of safety so we always recommend using batteries from reliable companies such as Bosch, Shimano, Yamaha (Giant/Liv), Brose (Specialized E Bikes) and Whyte Electric Bikes and use these with the supplied charger and if you require a replacement, only purchase the specific one for your battery.
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Charging modern batteries is very straightforward but there are a number of ways you can protect the life of your battery with some simple tips:
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If you are not using the battery for a number of months then it is best to leave it between 60 and 80% charge and then check periodically to keep it in this range. This will maximise the life of the battery.
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Leaving the battery stored at 100% will not damage the battery but will affect the lifetime of the battery as it puts stress on the battery to remain at 100%
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Do not leave the battery on 0%, especially not for an extended period as this can cause the battery to die and not wake up again.
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Avoid dropping or bashing the battery and if you do give it a significant knock, come and see us for a diagnostic test.
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If the battery or the charger is excessively hot when charging, immediately unplug and take it to an authorised dealer for a check (Note: it is normal to expect the battery and charger to be a little warm when charging)
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Be sure to update the software of your battery and motor when required. This will protect the battery and ensure maximum life of the electric bike technology.
Other components
Gearing
The choice of gearing comes into two broad categories – internal gears or external (derailleur) gearing. Both give different benefits.
Internal gears
As all of the gears are internal, there is a lot less maintenance or replacement parts required over the life of the bicycle. Because this is a more complex rear wheel, it can be a little more tricky to remove the rear wheel of the bicycle.
External gears
These are the gears that more people are used to, external gears (or derailleur gears) provide a wide range of gears and it is simpler to remove the rear wheel in case of punctures. The thing to watch out for involves the extra torque going through the cassette and chain on an electric bike. Because of this, chains and cassettes can wear out faster if you shift gears under load. You can now get cargo bike chains that can withstand the extra load of carrying the weight of the bike and any luggage/passengers.
Brakes
On most e-bikes you will have the choice between classic rim brakes or disc brakes (hydraulic or mechanical) and there are big differences between each. As electric bikes are heavier, brakes are one part to invest in and in particular disc brakes.
Rim brakes
Usually found on less expensive entry level e-bikes and will provide good stopping power on dry days and flat routes
Mechanical disc brakes
Disc brakes controlled by cable which give better stopping power than rim brakes particularly in wet conditions. As these are controlled by cable and not hydraulics, they can be a bit more effort to pull
Hydraulic disc brakes
Offering the best stopping power in all conditions and very little effort to pull. As most modern e-bikes are in the region of 25kg, it is definitely worth considering hydraulic disc brakes as they will vastly reduce stopping distance. Hydraulic disc brakes are a must, though, on Electric Mountain bikes (e MTB) as their sensitivity and stopping power is essential.