It would be terrible if one of your holiday chalets or hotel rooms were to catch fire because of a bicycle battery. It is, however, a real risk.
The battery is a vulnerable part of all electric bicycles. Even minor damage inside the battery can lead to a fierce fire. The battery first becomes extremely hot. This happens very quickly and the resulting fire is almost impossible to stop. Flammable gasses are released, which can even lead to an explosion.
What makes it difficult, is that you don’t know how guests treat your e-bikes. They don’t even have to be careless, a breeze can blow a bicycle over and that is enough to damage the battery internally, which you can’t see from the outside.