If a battery reads 3V with no draw (volt meters don't use much for the load to calculate voltage) then it might dip lower when in actual use. Once batteries start dropping in measured voltage from design voltage they are pretty much junk.

Are you planning on reselling them or do you have 100 old macs with dead batteries? I have 10 or so new PRAM batteries in stock so I am good for a few years.

You can get 5 new ones for a little over $2 a piece shipped on ebay, less damage to the hobby budget.