Hi,
Yes you can do Batu caves from Kuala Lampur in a day. Getting to Batu is real convenient in Metro. Get to KL railway station, you have to get to Platform 3 and there is a train that takes you to Batu Caves straight, look for signage signs for the station. You have to get down at 8th station to reach the Batu Caves station from KL sentral.
I have found a perfect post of Tripoto that will help you plan your trip to Batu caves, you can go through it and plan your trip. https://www.tripoto.com/trip/expedition-to-batu-caves-everything-you-must-know-5a1fa28c0a094