Might also be titled "How NOT to fit a battery charging cable!" :)
As people have said in the comments, you'd be better off picking up a live cable under the seat and then just earthing it somewhere on the frame. There's no need to attach the cable directly to the battery. I know this now, but all of my previous bikes have had batteries that were easily accessible, so this was my first thought.
NOTE: The CRF1100 has a Lithium battery. Do not fit a standard Optimate to it as it will kill the battery!! I have a Lithium battery charger on order.
I had read that people resorted to drilling holes in the back of the battery cover (AKA the tool case), so i went down that route first, but then found a better way to do it, but it wasn't obvious at the start.