I bought an MFLB and some powerex 2700 mAH batteries and I peeled off the labels and fully charged them but they wont power the MFLB when I press the battery in it doesn't turn on the light or do anything, the only batteries that worked are the ones that came with the MFLB, what went wrong?
try pushing the little ring that encircles the negative terminal (the entire diameter of the battery, and the negative tip. everything but the positive nipple basically). it may not be making correct contact as not every MFLB is 100.000000% the same in size. there are tolerances that some batteries do not fit in. also, entirely wipe away the sticky residue to clear that from a possible cause. the batteries aren't shorted either, right? and try pushing hard as fuck.