EVieBikes have a maximum range of 40 miles (65km). The battery level of each bike is shown in the app as a % value. EVieBikes with less than 15% battery remaining will not be available for hire.
Climbing lots of hills will result in a slightly reduced range - just like using your phone heavily all day results in less usage with a single a charge (good job we have our new phone charger for that!). It also depends on rider weight and weather conditions.
The battery level is visible on the bike display during your rental: