First Appearance: IPTSF Text 6
Battery Chargers have never been described, so their exact nature is unknown. It may be that they are siege equipment, similar to siege towers, it may be that they are siege units similar to wiener rammers.
On the one hand, when a group Haffaton's firemen ambushed Goodminton's column on the road to Goodfinger, they burned four siege towers and a battery charger, which may imply that battery chargers are objects. On another, battery chargers have never been seen to be used by any other side, which may suggest that they are a rare type of unit, as siege towers, for example, appear to be ubiquitous.
Real World References
A charger is a type of medieval warhorse