converting z3 to run on AA's ???

So I had this idea, what if my Z3 combat light could run off of AA's? The batt compartment is long enough, I was able to fit 2 end to end, and the tailcap switch works, I used a Cree R2 drop in mod (designed to replace the p-60 and p-90 series lamps) and it was quite dim... Obviously not enough juice in 3v to run a bulb intended to run on 6-9v. I am NOT a light techno-geek, but I assume the circut built into the R2 is designed to recognixe 6-9v, but not the 3v supplied by the AA's?

Is there a solution for this? Is it simple? Can it be explained in simple terms? Has this allready been covered in the forum and someone can direct me?

Thanks for the help.