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FAQ: Electric bike battery size - how is it measured and what does it mean?

As a rule of thumb, bigger battery size (capacity) means more distance travelled (range). Therefore, battery capacity is an important specification for an electric bike. Capacity is most often stated in amp hours (Ah). Some manufacturers describe capacity in watt-hours (Wh). In order to compare apples with apples, you will need to divide the watt hours figure by the battery’s voltage (V) (which is also usually stated prominently in the e-bike’s specifications). The majority of modern e-bikes run on 36 volts. As an example, an e-bike with a 36V/400wh system from Bosch has 11.6Ah.

What sizes are available? Some manufacturers offer big 17Ah batteries (like our Kalkhoff Agattu). Other e-bikes will have smaller batteries (the light and beautiful Faraday Cortland has just over 7Ah).

In practical terms, a smaller battery is sufficient for those people who use their bikes for shorter rides. Bigger batteries are best for those who have a longer commute, enjoy extended weekend bike outings, or like to use a little more help from the motor. To get better idea of the range you can get from different batteries, have a look at the battery range FAQ.