Nintendo Switch Battery Draining

My Nintendo switch just recently started acting up because the entire battery life was drawing in the matter of 1-2 hours when just left off. I sent it to Nintendo and they said it was water damaged so they can't fix it and so now I want to see if I should replace the battery or if it could be with something else. I'm a noob at taking things apart as is why I'm scared to try and take apart my switch before I know what's wrong. Any Ideas?