Battery voltage 12.6 Volts - fully charged
12.2 50% charged
11.7 (or less) fully discharged
Alternator is providing the adequate voltage - check belts.
You were on vacation, so I question wether the battery has had enough time to fully recharge. Put it on a charger overnight (u don't have to remove)
Battery connections, clamp them down and check for corrosion. ( I assume you put the battery in?)