So again, what’s the scale? With a full AA it should read 4+ mA? Just making sure I understand.
As I said, I — and others, it seems — have never heard of measuring battery capacity by current. Always just voltage under load. So it’s weird.
But again, the holder itself is cool. Perhaps it’d make sense to put a load resistor in it and then just use it in volts!
Did you DIY the contacts, or use COTS ones like from Keystone?
I used banana jacks (crappy ones that I modified) with the plastic cover removed.
I believe these here from Ebay:
https://ebay.to/2Fr4wmy These are really pretty bad. You have to solder the lantern to the post otherwise you have intermittent connectivity.
Regarding voltage/current...it is natural for us to think in terms of voltage. However, as I said, it does not matter for a given (known) resistance as long is there is some quality metric (e.g., 4mA is good, 3mA is bad) to inform the test result.
Voltage is no more informative than current because the usefulness of your battery depends heavily on your application.
The designers of the meter decided to add this feature...load the battery with a 370 ohm resistor and measure its current. It could just as well have measured the voltage instead. That was their choice--not mine. I would argue that the ONLY bad thing about measuring current vs. voltage is that we don't have an intuitive sense of what is good and what is bad (like we do with voltage--as I said...because we think in voltage terms). So the designers of the meter decided to give you a number, a threshold, on the dial.
I am posting a page from Linden's Handbook of Batteries which illustrates that there is no "one size fits all" method for testing a battery.