Battery Dead problems of the 2015 Subaru Crosstrek

Ever since the first battery died after a cold winter, the car has been draining the battery on it's own manner. Currently, once awhile, I will notice it drains much more overnight than normal, and if left unused 3-5 days, the car battery will be completely drained. Communicated with the dealer and Subaru, but consider the car has no issue and determined that it was my fault that I must be not driving enough. The first battery lasted from 9/2015 to 2/2017, been driving under same method, behavior, and condition before the death of first battery and after. However, even since the change of the battery, the issue exist and never fixed by dealer. A good note is that a towing company person had a same car with same issue, it was fixed by replacing the battery control board or such. However, Subaru and dealer didn't think that may be the possible cause. In this manner of the car, I can not trust the car to keep driving safely, or maybe it will not turn back on after a trip into mountain road and stopped for a break time. Battery is the key part to keep the engine firing and running. If it died in the middle of driving, this issue may cause death. The car had died in varies location. Such as home driveway, home garage, airport parking lot, and public locations. Yesterday, the car just died again inside the house garage. If needed, I can be reach any time with my phone. I just want my car issue being taken care of, and Subaru to see the issue before anyone get killed.