Google 'e-bike' and you're instantly bombarded with confusing information! They come in all shapes and sizes and in varying quality. This post attempts to condense all of this information onto one page, giving you the key points to consider when deciding what type of e-bike (if any!) is right for you.
(If you're trying to decide between an e-bike or an e-bike conversion check out this post).
WHAT IS AN ELECTRIC BIKE?
An electric bike, also commonly known as an e-bike or ebike, is a bicycle with an integrated electric motor which assists with propulsion. An e-bike is generally made up of three main components in addition to a normal bike. These are an electric motor to provide propulsion, a battery to power the electric motor, and some form of control unit or display to operate the e-bike system.
To meet the requirements of the UK law the electric motor must assist whilst the rider pedals it cannot solely propel the bike without the rider pedalling. It is allowable for an e-bike to be fitted with a throttle provided that the throttle function seizes above 6km/h (3.7mph), which is often used a walking function when pushing the bike.
The UK law (see this link) has the following set of rules regarding e-bikes:
Electric bikes: licensing, tax and insurance
You can ride an electric bike if you’re 14 or over, as long as it meets certain requirements.
These electric bikes are known as ‘electrically assisted pedal cycles’ (EAPCs). You do not need a licence to ride one and it does not need to be registered, taxed or insured.
What counts as an EAPC?
An EAPC must have pedals that can be used to propel it.
It must show either:
the power output
the manufacturer of the motor
It must also show either:
the battery’s voltage
the maximum speed of the bike
Its electric motor:
must have a maximum power output of 250 watts
should not be able to propel the bike when it’s travelling more than 15.5mph
An EAPC can have more than 2 wheels (for example, a tricycle).
Where you can ride
If a bike meets the EAPC requirements it’s classed as a normal pedal bike. This means you can ride it on cycle paths and anywhere else pedal bikes are allowed.
MOTORS: HUB DRIVE OR MID-DRIVE?
There are two main options for motor location on a e-bike. A hub drive has the motor located within either the front or rear wheel. A mid-drive has the motor located directly between the pedals at the bike’s bottom bracket. A mid-drive has a number of advantages over a hub drive, the main ones are listed below:
Greater torque (turning force generated), often nearly double than the equivalent power hub motor. Torque is needed for climbing steeper hills.
The motor makes use of the bikes rear gears which means greater efficiency and subsequently you can cycle further on a single charge.
A mid-drive motor is often more complex than a hub drive motor and it often also requires a special frame to mount it, both these factors mean a mid-drive e-bike is often more expensive than a hub drive e-bike.
Pedal Assist Sensor (PAS)
The pedal assist sensor (abbreviated to PAS) is the component which effectively turns on the motor when pedalling commences.
There are two common methods of PAS, these are speed sensing and torque sensing. A speed sensor generally works by monitoring movement of the crank arms (the metal arms which the pedals attach to). Once movement is recorded by the speed sensor the motor starts spinning. The amount of power provided by the motor is constant and can be altered on the display often mounted on the handlebars.
Torque sensing is more sophisticated than speed sensing. The torque sensor monitors the amount of force being applied through the pedals by the rider. The more effort the rider puts in the more the motor assists. The maximum power provided can be further refined by adjusting the power level on the display. Torque sensing gives a more natural feeling of cycling.
Some e-bikes make use of both speed and torque sensors.
Batteries often make up a significant cost on the e-bike. Most modern e-bike batteries are made up of a large number of individual lithium-ion 18650 cells (like large AA batteries in appearance) which are contained within a plastic case either mounted on top of or within the bike frame.
Battery capacity is often measured in amp hours although watt hours is a more useful figure as this is the actual energy contained within the battery which translates into the range it can provide. Watt hours is calculated by multiplying the battery voltage by the amp hours, for example a 36 volt (V) battery with a 14 amp hour (Ah) capacity has a watt hour capacity of (36 x 14) 504 watt hours (Wh). A 48V battery with a 10.5 Ah battery has the same Wh capacity (48 x 10.5) of 504Wh as a 36V 14Ah battery. Which in theory means a 48V 10.5Ah battery would provide the same range as a 36V 14Ah battery.
It is recommended that only batteries containing genuine Samsung, Panasonic, LG etc 18650 cells are used. There are many cheaper batteries available which use unbranded 18650 cells. These are often unpredictable with regards to their longevity and safety when charging. There are a number of news articles online of e-bike and similar batteries catching fire whilst charging, these nearly always occur with batteries containing unbranded cells.
A battery containing good quality branded cells, if looked after, should last at least 500 cycles. This means the battery can be discharged and recharged 500 times before the capacity reduces more than 80% of the original new capacity.
If you're looking to find out more about e-bikes we've found this site to be a great source of information https://ebikechoices.com/ or check out our post Conversion Kits vs Factory Built E-bikes to find out more about conversion kits.