Been using V2, slim cartridge for 5yrs ,only occassional will one cartidge not work on battery, but always work on one of my other 4! Do not fill to of tube within cart. Do not over tighten to battery. Refill before 1/4' is left, you may burn out small fliters in cart. Make sure you tip fluid to run down inside of cart. Not straight small center tubing. Last my only gripe is filters are on back order alot, probably due to incorrect filling, making need for careful fill, as to use cart. over many x's..any help?