Starter battery is not charged , alternator in order

Hello Phaeton municipality. My Phaeton gp3 Bj 11, 3.0 tdi no Keyles Go power problems. The starter battery is not charged, so new battery worry the battery is 6 weeks old, against the same game Holds about a week and I have to charge it from the outside. Voltmeter shows whether engine is on or not at the starter battery about 12.9 volts on. At the comfort battery at running engines about 14 , 5 . At the plus pole in the wire harness engine compartment at the front right , I get on the left side harness without pimples with running motor 14.5 volts which is also mounted to my knowledge on the alternator. The right cable strand with pimples is mounted on the starter also 12.9 volt hedgehog whether the car is running or not. What do you think could be the error? Did any of you have the same problem?