Imagine the scene. It's half way through an investigation and things start kicking off. Your camera batteries have just died and you go to get some more but you've run out. Oh no, disaster! Because of the large number of batteries that the group generally get through during an investigation, we always use rechargable ones. During an investigation, if a set die on us then whilst we are using another set to keep us going we can quickly stick the dead set into the charger and leave them in there for an hour or so. That way, if the current supply ever run out before an investigation ends then there's always an emergency set ready to go.