I'm interested. How did you do that measurement? I'm thinking a couple of pieces of brass shim separated by tape, between the battery and the case contact?
I don't know how @Dabbler did it. But if it were me doing it, I'd just put power leads onto the battery terminals inside the Caliper. I have a wide variety of probes and clips that might serve that purpose well.
I might also be inclined to use a regulated power supply instead of a battery so I could evaluate current draw at various stages of a battery's life.