Recently, after getting some very short performance life out of my batteries that are used in both the D700 and D300s, I was wondering if anyone knows how to/ where i can take my batteries in their "fully charged" state to test if they're performing to the right voltage?

Ive got one battery that came from my preivous camera, the D200, and then one each from my D700 and D300s, but haven't had a way of marking which was which.
any help, tips, comments or places i can go to get this (cheaply) tested would be much help!