2000 1500FI Trouble starting

[law2339]

Hi Guys . Just joined.
I have starting trouble with my bike. Had to mechanic and checked battery, starter, voltage regulator and all electrical. The problem is sometimes it starts fine but other times it won't and after trying a few times the battery dies. As soon as I boost it will start instantly.
It almost seems like not enough power in battery to turn it over fast enough to start. I tried a new battery without success, took starter off and had checked. Even looking at buying a battery boasty pack to carry with me but pretty not cool when you stop for gass and everyone is looking at your bike and when you go to start nothing.
Any suggestions.