So true, the voltage drops tell most of the story, and knowing the current at the same time is a bonus. Where are the needle meters and carbon piles these days? :)
Don't know 'bout you but I still have a couple. I have a charging / starter test setup I bought at a garage sale. I forget, it's a big name like mac, and an old autometer pile. The meter on it is junk, but the carbon pile is fine