If you are looking for a dehumidifier that will remove excessive moisture from the air in your RV, then you definitely need a small portable unit—one that you can easily move in and around your RV. Most car dehumidifiers are fabricated to work in small spaces. Depending on the levels nuisance caused by humidity in your car, there is a variety of units to choose from. You can go for small battery dehumidifiers or simply use the desiccant dehumidifiers. However, since your problem seems escalated—dampness and probably a nasty musty smell—you need a dehumidifier that will work quickly to remedy the situation. Read more about portable dehumidifiers here. Also have a look at small dehumidifiers here.