I have a hard time keeping my Samsung Galaxy S3 battery charged.

[AC Question]

I read somewhere about the task manager, so when I go to t he task manager and select "RAM" then hit "clear memory" there are as many as 45 or more applications running which I'm sure is what is causing a short battery life. I have noticed my battery holding better charge when I clear the memory often. My question is...what app's. can I disable to keep this from happening. I don't use that many app's, but I'm afraid I'll disable something that is needed in the running of my phone. Any help and advice would be greatly appreciated!