The distributed computing system relies on a computer message to tell various modules to shut down when you turn the car off. If one or more of them is not getting the signal, it will discharge your battery. If the sensors are not reporting the actual voltage reading of the battery, it won't get charged. A static discharge test should show if the system is drawing excessive power when off. The clock, alarm, and remote entry systems don't use a huge amount of power, and the normal range of discharge is known...it's not that hard to measure, and should point to the problem. It's also not hard to test the DC-DC supply that provides the 12-vdc.