If the charging system is operating properly (and the vehicle should throw a warning if it isn't)... then it sounds like there might be a damaged plate in the battery. It happens. Take it to a local auto parts store and generally they are happy to give the battery a full test and see what is up with it.
Note: you can verify the charging system using a volt meter with the vehicle running and in park. It should read ~14.5 vdc on the battery terminals. You also want to do have it checked for ripple (caused by a failed diode) too... and an auto parts store can do that, or you can do with a low cost simple battery testing unit. Example: https://www.amazon.com/gp/product/B01M0ARG3X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Note: you can verify the charging system using a volt meter with the vehicle running and in park. It should read ~14.5 vdc on the battery terminals. You also want to do have it checked for ripple (caused by a failed diode) too... and an auto parts store can do that, or you can do with a low cost simple battery testing unit. Example: https://www.amazon.com/gp/product/B01M0ARG3X/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
