I have the infinity and was using the batteries that came with it. One of the batteries went dead and I bought some new ones and they didn't seem to operate the infinity. The new ones I got are the ultrafire 14430's. After looking at them for awhile trying to figure out why they didn't work, I noticed that the ultrafires didn't have the + side buttons that stick out enough to contract the - side of the second battery when placed in the tube. I then trimed a little of the covering on one of batteries so it could touch the other one's - side when placed in the tube, the infinity would then work just fine. Should there be any problems with part of the battery covering being trimed off? The other thing I noticed is that the back cap is a little tighter than with the starting batteries, is that anything to worry about?