The battery – among propulsion and frame - is one of the most important components of an e-bike and most of the time it is the most expensive piece of an e-bike. There are many different types of batteries.
Principally, when buying an e-bike you should make sure to examine power (mostly specified in WH) and weight. What also matters is the number of charge cycles of a battery. On average there are between 500-700 cycles which corresponds to an average usability of 4-5 years.
It is also important whether the battery is detachable and therefore could be exchanged and also for how long hat ebattery will be under guarantee by the manufacturer. Furthermore you should assess the availability of batteries in the future. The advantage of a detachable battery is that in most cases you can charge it independently from the bike. So you do not have to carry your entire bike to a socket. If the battery is detachable it should be lockable to the bike though, so when you want to leave the battery on the bike and not want to carry it with you, it does not get stolen.
Make sure if the position of the battery could be obstructive in any way. For example it should ideally be possible to charge the battery while it is still attached to the bike and also the battery should not be obstructive when mounting a baby seat or a pannier.
It is very important how much spare batteries cost. This is the only way to evaluate if the price of the e-bike meets the desired criteria. At the moment it must be assumed that with a regular use, the durability of a pedelec absolutely exceeds those of a battery. A spare battery will therefore be needed in any case!
In general capacities of a battery are specified either in ampere-hour (Ah) or in watt-hour (Wh) but WH offers/provides a better comparability.
Capacity and weight are the the decisive factors for the price of a battery.
up to 250 Wh: batteries with low capacity up to
350 Wh: batteries with average capacity above
350 Wh: batteries with large capacity
Overall, pedelecs are built with one of the four following types of batteries: lead acid battery, nickel-cadmium-battery, nickel metal hybride battery and lithium ion battery. They differ significantly in weight and memory capacity and acordingly in the price.
Even after 1.000 chargings a NiCd-battery has more than 85 percent of its actual capacity and is then considered as worn out.
Further problems arise when the battery is not charged completely at irregular intervals – this will lead to the so called memory effect. The memory effect leads to a considerable/significant reduction of the/in capacity.
NiMH batteries enable up to 800 charge cycles. In comparison/compared to NiCd batteries they have a higher energy density and can store more energy at/for the same weight. However, even with NiMH batteries at irregular chargings, the memory effect occurs.
Li-Ion-batteries are the most advanced and simultaneously the most common batteries for pedelecs. Due to their high energy density (about twice as high as of NiCd batteries and about 50% higher than NiMH batteries) you can store more energy at a relatively low own weight. Another advantage is that no memory effect occurs with Li-Ion batteries.
Currently the development of batteries - especially in the mobility sector – is dynamic and it achieves increasing capacities and power and also decreasing weights of batteries. The increase of range depends - among others – on exactly these factors: the lighter the total weight and the higher the battery power, the greater the range.
Durability of batteries is limited and they have to be exchanged after a certain time. The shorter the durability and the higher the price of spare batteries, the more expansive the purchase of the bike in terms of the actual utility. Therefore it is urgently necessary to ensure to follow the manufacturer’s recommended use.