What could be causing my truck's battery to drain when parked for a few days? on 2013 Ford F-350 Super Duty

Shortly after taking delivery of my new truck I started to have problems with the battery being dead after it was parked for several days. I only use it on weekends and it will often be dead when I go to start it. I have no accessories plugged in. The Ford dealer can not find any problem with it and the battery checks out good when tested. Over the course of the summer I have had to jump start it several times. When I turn the truck off and exit the cab I can hear a "whining" sound that goes on for several minutes and then quits. Any ideas?

1 answer 2 comments
Did Magic City Ford check it out? They are usually pretty good! Possible battery problem, ask if they checked the batteries with a hydrometer. If one battery has a problem, have both replaced!! It's a new truck, tell the dealer to fix it!
You have the right dealer. I am not sure exactly how they checked it but will inquire next time. This is a gas engine truck so it only has one battery. Thanks!
Ok, 6.2 was thinking i read F-350 Super Duty 6.7 which is (diesel),, same deal though as far as what they should do! At one time i knew some ol boys that worked there which came in very handy but i guess they have since hung up the wereches or suits & ties for good by now.