remove the seat, remove the battery strap, disconnect the battery cables......negative cable first.....and lift it out.
let me know if you need more help.
will it lift out?
I was just reviewing the parts book and it no longer shows a strap.(actually....it doesn't show anything holding the battery in)
try looking down around the battery with a flashlight and see if you can see anything holding it into the oil tank.
it may just be stuck.......
sounds like it's just stuck to the mat....try wiggling it back and forth.
there isn't much room in there and the parts book shows no clamp.