Found some info.
From the Robinson Helicopters Owners Group:
Battery placement is assigned by the factory, and is not a buyer-selectable option. The frame (port side, engine compartment) installation is the preferred location. Before an aircraft is built, a preliminary w&b analysis is calculated, using the various features selected for a specific helicopter. If the analysis predicts that the CG with frame battery is too far aft, the ship is built with an under-seat battery. The target is to have the CG be at 102.5 with full fuel and a pilot.
The R44 Maintenance Manual says the following:
The battery is in a fiberglass container located on the lower left steel tube frame, in the nose under upper console, or in the left-front baggage compartment. Police and E.N.G. versions have the battery suspended from the tailcone.
Apparently battery placement was also a choice you could make many moons ago when you placed the order for the helicopter.
@firebird_uk: Google the "ebook from Tom Venuto" to solve your w&b issues for good.