What about using a watt meter and an tenergy b6+ multi chemistry charger balance charger to test the charge/discharge mah ratings? You want to be careful, but i think with a arduio pin headers, and female female pinleads to a balance port, inline with the wattmeter you could get a very accurate battery health reading. Can set discharge/charge mah ratings as well.

Might just try this on my n810's 1500mah lipo to see how it works.