If an e-bike will be unused for a while, its battery deserves more thought than simply leaving it on the bicycle until the next season. For longer storage, a Bosch eBike battery should be kept at 30–60% charge. Remove it from the bicycle if the design allows.
A dry, ventilated space is suitable, ideally at a temperature between 0 and 20 °C. Keep the battery away from heat sources and flammable materials, in a room with a smoke detector. That is a more considered choice than a damp or crowded corner where conditions are hard to control.
Before charging, check the casing for damage and use only a compatible charger. Charge under supervision in a dry, ventilated place, then disconnect the charger from the mains. A damaged battery, or one that needs inspection, belongs with a specialist dealer rather than being opened at home.