by Yvonne Wyss
26 February 2020

Do you understand electricity?

Every e-bike battery comes with information about ampere hours, watt hours and volts. It isn't always easy to understand these physical units and to know what each of them means. Is everything clear to you?



Many people have probably heard of volts (V for short), the units used to measure electric potential, which is required for electricity to be able to flow. Broadly speaking, it can be said that electric potential develops when there are separate electric charges. This means that somewhere there is a greater negative charge than positive charge. To enable electricity to flow, these separate charges need to be connected through a suitable conductor.


This state can be illustrated using two bowls of water at different heights. The difference in height symbolises the electric potential and only allows water to flow when there is a suitable connection between the two bowls.


Electric current, which is measured in amperes (A for short), develops when there is electric potential. And as mentioned above, there needs to be a conductor so that the electric charges can counterbalance each other and flow. Let us return to the example using water where potential is described as two bowls at different heights: in this case, the conductor is a connection joining the two bowls. Electric current corresponds to the flow of water, but with electric particles flowing instead of water. This electric current is then indicated in amperes.


The current is often listed on chargers. There are, for example, chargers with a current of 4 amperes and others with a current of 6 amperes. The higher the current of a charger, the faster a battery can be charged with it, because – to put it bluntly – there is more electricity flowing. However, not every charger is compatible with every battery. If you would like to purchase a new charger, your FLYER dealer will show you the options available to you.


Ampere hours

An ampere hour (Ah for short) is a unit of measurement for electric charge. It indicates how much electric charge flows through a conductor in one hour at a constant flow of electric energy of one ampere.


Battery capacity is often indicated in ampere hours. A charger with a current of 4 amperes, for example, transports a charge of 4 A x 2 h = 8 Ah within two hours. A battery like the FLYER Smart Integrated Battery SIB-630, for example, has a capacity of 16.75 ampere hours. If you charge this battery for two hours, you will achieve a capacity of 8 Ah (charger current, i.e. 4 A, multiplied by 2 hours’ charging time), which corresponds to about half the total capacity of the SIB-630 battery (16.75 Ah).


If you know the current of the charger, it is relatively simple to calculate approximately how much a battery can be charged over a certain period of time. However, this simple calculation may result in slight differences from the actual charge level. As most e-bike batteries have a battery management system that, among other things, protects the battery from overcharging, batteries are usually no longer charged with the charger’s full current once they reach a charge level of 80%.


Watt hours

The watt hour (Wh for short) is a unit of measurement for energy capacity, e.g. the amount of energy in an e-bike battery. The larger this amount of energy, the larger the “tank” of the battery. The amount of energy in a battery is calculated using the battery capacity (measured in ampere hours) and the rated voltage of the battery (measured in volts).


The FLYER Smart Integrated Battery SIB-630 provides 630 watt hours. One watt hour means that a performance of one watt is sustained for one hour, or that a performance of two watts can be sustained for half an hour. This means that a SIB-630 battery can, for example, provide 630 watts for an hour or 315 watts for two hours.


You can decide for yourself how much boost the e-bike motor should provide by setting the assistance level. However, the actual distance that can be covered with the amount of energy in a battery until the “tank” is empty depends on many more factors than the size of this “tank” and the selected assistance level.