On many electric bikes you have the choice of either leaving the battery pack on the bike or removing it during charging.
The safety circuitry of most chargers (and battery management systems) ensures that the battery cannot be overcharged. However, it is always best to disconnect your battery from the charger once it is charged. Ensure the battery is diconnected within 12 hours.
Charging when the ambient temperature is below 0C or above 40C can lead to insufficient charging and be harmful to your battery.