Might need to get a flashlight and see if the contact way up inside the battery tube isn't gunked up, if it is might need to get some of those really long q tips, rubbing alcohol or some other contact cleaner and see if you can get down in there to clean it
GC Electronics 50 PC 6" Long Double Headed Cotton Cleaning Swabs Q Tip 10 270 | eBay
Also snag you a multimeter and check to make sure you batts are charging, wouldn't hurt to run a papertowel with rubbing alcohol over the connectors on the batts, and clean out the end cap (aka anywhere the electrical connections actually touch...gunk/juice/corrosion could cause bad connectivity and result in the low voltage readings.
Here is a HUGE thread on the vmax..might be something in there too
http://www.e-cigarette-forum.com/fo...-smoktech-vmax-owners-tips-tricks-quirks.html
Good luck