All new Hondas come with a five-year, 60,000-mile powertrain warranty and a three-year, 36,000-mile limited warranty. The powertrain warranty covers all the mechanical parts that drive your Honda, such as your engine and your transmission. The limited warranty covers just about everything else.
Since your alternator is an electrical component, not a mechanical component, it is covered by your Honda’s limited warranty. As long as you haven’t exceeded the warranty’s timeframe or mileage limits, you should be able to have your alternator repaired free of charge.