The cable for the battery unit terminates with a small pcb edge connector on the battery end, this cable can be carefully slid out of its slot and placed aside until the end. The small pcb is held in with a small clip, which can be easily poked to freedom. Huzzah! The designers used small spring contacts to provide the connection from the batteries through to the pcb, this makes everything easier. The pads are marked with a tiny + and - symbol to show the batteries polarity, but who needs those when there is a nice big sticker on the plastic indicating the positive terminal :).
I picked up a 4xAA (series connection) holder from the local Jaycar as well as 4x NiMh batteries. The wires were shortened to around 20mm and then soldered onto the pads on the battery controller pcb.
This was all the (really hard) wiring that was required.. Next was a matter of using some double sided tape to attach the pcb to the battery pack. Also note a small amount of double sided tape was also placed between the pcb and the cables connector - the old plastic case used to hold this connected on place, however now i am no longer using that unit some tape was added to hold the connector in place.
No stuffing around, nice and easy… The batteries almost fit into the mouldings for the official battery units, close enough they do not obstruct the airflow. On the plus side the batteries are now also significantly larger in capacity which should help in runtime :)