The battery is behind and above the front light.
Sitting on the seat, looking forward, on the left hand side you will see a number of screws holding the front cover on. Undo the top two. Do the same on the right hand side.
Go to the front and from the top, gently prise of the front cover and then you will see the battery.
FYI, The front cover is in two parts, top and bottom.
Garryj, January 2014