A battery is almost always the single most expensive component of an ebike. Modern lithium-based ebike batteries offer a wide range and last for a long time, if treated well. Even the best batteries however need to be changed after some time. You may be tempted to save some money on this expensive component, but that wouldn’t be a smart choice: the best batteries cost more, but also guarantee a much longer durability, enabling you to save money in the long term. This is the result of a research conducted by the ADAC.
The German ADAC is concerned not only with cars, but also with bikes. In their labs they have tested two kinds of ebike batteries, both lithium-ion based: one costed about 500€, and the other about 300€; the batteries had the same capacity (Wh). They have then simulated a normal use of these batteries, charging and discharging them many times.
The results of the test on ebike batteries
The higher-priced battery has kept 80% of its capacity even after 700 charging cycles. The 300€ battery instead dropped to 80% of its capacity after 500 cycles (even this is a quite good result, we would say).
Where does this difference come from? A battery is typically composed of a dozen cells. Even batteries composed of cells made by the same producer can differ in quality. Not all the cells are born the same, and the most careful producers test their cells, using only the best ones to make their batteries. The difference in price and performance usually depends on these factors, and on the chemical composition of the cells.
Of course anybody can take some low-quality cells and sell them at a higher price, so paying a lot of money for a battery is not automatically a guarantee of high quality. The lesson we can draw from this research is not to save too much money on a battery. Generally, remember also to buy a battery with a capacity which is 20% higher than what you really need, exactly because their capacity tends to (slowly) degrade over time.
Another aspect underlind by the ADAC researchers is the necessity to carefully use and care for the batteries: this has a high influence on how long they last. In daily use, it is batter to charge the batteries when they are at 20 to 80% of their capacity, without recharging them too early or too late. If you don’t use your ebike, the battery should be stored when it is about 50% charged; control the state of charge of the battery at least once a month, and bring it to 50% if necessary.
For other details you can consult our page on ebike batteries.