I'm not sure about specifics there. It's an interesting thing to think about though... whether a battery with exposed leads has more potential to short vs being attached to something. (I would assume the exposed leads would be worse.)
You never ever leave leads exposed. That is absolutely the fastest way to start a fire. Either pack it with the equipment, or make damn sure you have some industrial covers for those leads.
And yes, I have had people do a piss poor job securing their leads, and then have the equipment rub up against metal, and "Poof" - instant smoke. (Thankfully the luggage was with us, so we were able to stop it before it became a fire)
