But basically nothing does well in the estimation of capacity especially when it comes to sulphation. However, a measure of the internal resistance will give you an approximation of how sulphated a battery is.I never believed those CCA values from the AAA roadside battery guys. Those handheld testers use a momentary load and math to get an estimated CCA value.
"Mechanics prefer small sizes and device manufactures have developed handheld testers, which induce a momentary high-current pulse that corresponds to the entered CCA value. Ohm’s law calculates the internal resistance on hand of the induced voltage drop, and the device provides a CCA-equivalent reading. This test method is fast and convenient, but it does not estimate capacity."