Bring it to a Motolite shop (or any reputable car battery store you want). They have the necessary instruments that can check both the battery’s health and the vehicle’s charging system. The service is free and you can always go to a different shop to get a second opinion.

In my personal experience, in most cases, I was able to bring the battery back to health by charging it with a proper battery charger for several hours. Your mleage will vary depending on the battery’s age and how well it was maintained. I’d do this first before considering replacing it.

Unless absolutely necessary, don’t use the vehicle charging system to charge a depleted battery. This puts a lot of stress on the circuit and can accelerte wear on the alternator brushes, among others. If it can be helped, always charge a depleted battery using an external battery charger.