You need to get out more, Clark.
Batteries can show acceptable voltage and not perform under load. Replaced my daughter's battery in her van the other day that showed acceptable voltage, yet when they checked it at the store, it came up bad. Kinda like the bad nut in Willy Wonka (Johnny Depp).
You can load test the battery yourself. Put your voltmeter across the battery and then hit the starter. If it doesn't maintain at least 9 volts while trying to crank the starter motor, it's a goner.Battery Load Test With a Multimeter