Like the battery in a phone or laptop, an e-bike's lithium-ion battery degrades a little with every charge cycle — but how you charge and store it has a real effect on how gradual that decline is.
Charging habits
Frequent partial charges are generally easier on a lithium-ion battery than always running it down to empty before recharging. Unplugging once it hits 100% rather than leaving it on the charger for extended periods, and avoiding charging immediately after a ride while the battery is still warm, both help reduce long-term wear.
Storage
For storage longer than a few weeks, most manufacturers recommend keeping the battery around 40–60% charge rather than full or empty, in a cool, dry place out of direct sunlight. Extreme heat is particularly hard on battery longevity, so avoid leaving the battery in a hot car or garage during summer.
What actually drains range
Beyond the battery's raw capacity, range on any given ride is affected by assist level, rider weight and cargo, terrain, wind, tire pressure, and temperature — cold weather in particular can noticeably reduce usable range. Riding in a lower assist level and keeping tires properly inflated are two of the simplest ways to stretch range on a given charge.
Signs it's time for a new battery
A noticeable drop in range compared to when the bike was new is normal over time, but a sudden, sharp drop or a battery that won't hold a charge at all is worth having checked rather than assumed to be normal wear.