title_body: What can I do to improve this cold-brew method?
upvoted_answer: The problem is probably temperature of the water when steeping. For a better, more full-bodied result, steep at room temperature. Seattle Coffee Gear, for example, did a test of cold-brewing in the refrigerator and at room temperature, and reported that the room-temperature-steeped cold-brew was tastier, stronger, and more full-bodied. See also this question for more.
  
  In sum, don't refrigerate it until it's done brewing. Your fridge slows the extraction process down.