Stress with the Lima-strange loading behaviour of l300, 2.4i

Hello together, I installed a new Lima about 2 months ago, ran without problems until about 2 weeks ago. But suddenly no more juice on the battery. Voltage with multimeter of battery measured with the following result: Engine off: approx.12.5V engine started: approx.14.3V consumer on (light, rear heating, ventilation) approx.14.1V engine after a few minutes in idle and consumer on: 11.9V consumer then off: approx.14.3V ??????? Who can help me there? Battery pulls itself after a few dogs km imm It’s empty again, so I don’t dare to go on with light and heating. If it’s Lima, why is everything normal at the start? Thanks in advance