The battery is always connected up to an Optimate but I have noticed the problem so far has only occured when starting the bike on no throttle. From cold my bike doesn't like having the throttle used on start up. If the engines warm and I blip the throttle on start up (which will kick in the alternator) I have not had the issue so you maybe right on the current draw. I do wish there was a traditional on/off switch for the headlight tho!
How old is the battery? depends on it's life so far, have found that BM batterys only seem to keep there peak for 12 months, after that they still work but do not have the punch that is needed, thats when I go for a Hawker.

with 12 month warranty and full fitting instructions 


...and my brother and the some other mates from the Cretan V-strom club were so impressed that they want to know if you are planning to make a version for other motorcycle also...for V-strom's for example
)