Hi and welcome.
There are two ways the battery is charged. First is from your engine alternator while driving. Second is from the converter when hooked up to shore power at the camp site. If the battery is not charging or more likely not holding a charge, you need to take it in and have it load tested. If it is more than 4 years old, it is probably toast and you will need a new one. Either way a good battery shop can check things for you and tell you what you need to know.