1992 BMW 525i - Trouble Starting Sits Two Days

After rehabbing this wonderful five speed and replacing battery and trunk wires - it still will not start without a portable battery jump after only two days of sitting in my driveway - if driven daily, starts right up. Cannot seem to find where the drainage is - I use a reputable BMW repair shop and they have performed all other repairs but this keeps happening. Any advice would be appreciated here in St. Louis.

They should be able to put a load meter on the system…and then just start pulling fuses until you find the culprit.