All lithium-ion batteries discharge over time. If you store a battery too long without charging it, the cell voltage can drop to a "sleep" state which can be harmful to the battery. To avoid this, it is best to practice the following:
1. Never put a bike with a depleted battery into storage
2. Charge a Faraday for at least one hour every three months
3. For six months of storage or longer, charge the battery to 80%
4. Do not store a Faraday for longer than one year
*Note leaving the battery plugged in does not mean it will continue charging. Once the battery is fully charged the charger will disconnect, and needs to be unplugged from the bike and plugged back in again in order to begin charging.