I've had my 2013 SE C-max in the shop Tuesday - Thursday, they started by testing battery (3rd new battery needed) previous 2 new batteries at about 20 months and 38 months. First replace under warranty, second partial replace. Have had dead battery flatbed tow to dealer 3 times now. I'm the original owner.
dealer mechanic is working with Ford, they're down to the Body Control Module showing a drain that shouldn't be there ...so ford is having them test every electronic component in the car that's controlled by the BCM. Still no determination as to cause.
I own two 2013 c-max - the other one is an SEL - it hasn't had the battery problem but it had a defective Radio control that wouldn't turn off. They had to replace some other electronic module. Cost us $100 under extended warranty.
I've started researching the lemon law on these cars. My 2013 SE certainly qualifies as a lemon. When I was a kid we called FORD "Fix or repair daily"It seems their electronic component engineers are trying to return to those days.