Old batteries

Hows it. So collected an ice cream container full of old batteries over the years out of headlamps, gps ect. Always taken new ones out hunting ect. What voltage should they read if tested with a multimeter to check if they are half rooted ect? Aa, aaa, c and d size, obviously they have a voltage printed on the side but what does this translate to when actually used in a device? Any one know? Do they lose voltage at a steady rate? Or slow in output to a pretty much useless level of remaining voltage? Cheers

I know my rangefinder won't go if the battery is 2.85 volts for a 3volt.
But have a feeling that it is 15% below stated

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I don't know for sure. But I've been told that if there under then there done. 15% sounds good