With regard to Li-ion battery fires, if they are charged at too high a voltage and consequently begin to overheat there is a risk of catching fire. But what about after they are charged properly and just sitting around. Is there still a risk of something happening? For example, is my rattle gun that has been sitting in the shed for six months untouched something to be concerned about, or should the battery be removed and put in a strong metal box? What about as the battery gets older despite not having done hardly any work?