Power adapter question

You know how when your MBP is completely charged and say you walk off with it and come back to plug it in and its at lets say 96% and it doesn't charge it just runs off AC power? Is there a way to force your MBP to run off AC power for users who use there computer basically all day and don't want to scar the battery? This wasn't brought up in the battery guide set up by macrumors when I read it recently...And Im talking about the new MBP's where you can't take the battery out.