Is my battery permanently degraded, and should I consider a new one?

What is your question?

While driving back from the OBX to Hampton, VA last night, our 1500 Silverado's battery light started intermittently flashing. By the time I noticed it, the voltage was starting to fall from about 13 to 11, then as soon as it dropped to 9, the gauges completely cut out. I was able to stop and get a tow. This morning I replaced the alternator and charged the battery. Unfortunately, the battery charger seems to only charge to 70%. The battery was installed only three months ago back in February. Is it possible that this battery is permanently degraded by running the engine until the gauges/battery failed? Should I try leaving the battery charger on overnight to see if it can exceed the 70% threshold? The truck starts now and registers just slightly over 14V on the dashboard gauge. I'm trying to determine if I should (or even can) return the battery since it is under warranty. I'm not a "car guy" here, so this is all new to me.