As E-booger noted, voltage is not necessarily the sign of a good battery; only a quality load tester can determine if a battery is "good".
I believe in high amp load testing,
and use a 130 amp Mac model number B17300 that has been durable.
PulseTech company says the computer program inside their charger
tests for “Charge Acceptance” to rate battery capacity in a superior way to just voltage.
They list USA Patents
7834592B2
8269465B2
8269466B2
I wonder personally if measuring the
“internal impedance” of a lead acid battery
is of “real world” value.
This can be hand calculated by measuring voltage at two (or more) different amp loads.