About accumulators in e-bikes and pedelecs

The charge capacity that an accumulator can store is given in ampere hours (Ah). If an accumulator is not used, it loses a part of its stored energy. This electrochemical self-discharge is very low in modern accumulators, which are used in electric bicycles. Neither is there a memory effect. Nowadays mainly Lithium-ion, Lithium-ion-manganese and Lithium polymer accumulators are used.

The charging times of accumulators vary and differ from about two hours to up to eight or nine hours for a full charging cycle. Make sure to follow the instructions of the manufacturer in order to guarantee a maximum working life. For example, only use the original battery charger that belongs to it. Lithium-ion batteries are usually not able to stand frost – take this into consideration and do not store your accumulator in an unheated shed during the winter.

In practice, several factors influence the distance you can cover with a charged battery: the weight of the cyclist and of the load of the bike, ascents on the road, headwind or the degree of support of the electric drive. Also riding habits, as for example the speed or very frequent stop-and-go, influence the distance you can cover. Therefore information supplied by the manufacturer can only be an approximate estimate – the actual range heavily depends on the individual riding habit.

Accumulator and battery charger – latest safety norms

Accumulators of electric bicycles are getting more and more complex. As they carry out many functions of the battery charger, the battery charger itself increasingly takes over the function of supplying power via the building’s electrical supply network. The intrinsic safety of a modern accumulator that must be achieved is not reached with out-of-date standard tests on minimum level for conventional cells and batteries. The functionalities that exceed the actual energy storage are not considered by the usual guidelines and norms. Furthermore characteristics that are relevant to practical application are not examined. The accumulator of an electric bicycle, which can be removed, may drop to the floor or get wet because of rain or water while cleaning. This is for example simulated in a drop test according to a test principle of the "GS-Zeichen" (“tested safety” – a German safety approval). Standardised test principles can be adapted quickly to latest developments – in the case of norms this process takes years and thus always represents an obsolete state.

Drop test during the charging cycle

The test is run with an accumulator that is charged at least 80 percent. Up to 24 hours after the test the accumulator must not present a risk (fire, outgassing etc.).

The accumulator is dropped five times onto an even, smooth steel plate (or a similar hard floor covering) from a height of 0,85 m. The accumulator is held in the same position as if being held by hand.

After that it is checked for visible damage on the outside. 24 hours later it is checked again and a functional test is run.

Source: PM velotech.de GmbH