But it's also important to realize that apps that are currently open in RAM aren't necessarily active. If an app isn't in the foreground, or doesn't have a service that is actively doing something in the background, then it's essentially paused, and shouldn't be using CPU or battery. My concern with any app that tries to "clear up RAM" is that it works counter to how Android is designed (which is to keep RAM relatively full--typically about 70-80%). They can be useful if there's a poorly coded/optimized app that is taking up too many resources in the background, though.