Part of the problem with using a multimeter to test is a dead flat lithium primary can read 2.7v open circuit on the multimeter. I checked some some drained batteries that my M60 had drained fairly thoroughly (they were over 2 hours in, and very dim at that point). While they read 2.7+ volts and would turn on the M60, when connected to a 2.2 volt 1amp incan lamp they wouldn't even make it glow, and voltage under load dropped to zero, for comparison I checked a brand new cell and it lit the bulb brightly and read 3v under load. I haven't used one but one of the ZTS testers I think is a solid investment.