Hello, my Audi started earlier without any problems up to -10°C (we had eight weeks ago). Since I installed a Hifi system (1x 200W RMS, 1x360W RMS +1.3F Cap), it seems to me that either the battery (58Ah) would not be charged properly anymore. The generator has an output of 50/90Ah. In theory, the maximum current consumption is 50,6A (RMS power x efficiency). That is, the alternator would have to be switched on if I did not switch on additional consumers and I d even if I have to charge the battery 5min. before the end of the journey, the battery should be charged so far that a restart is possible (at +10°C)? Oh yes, while the engine is running, I always have a charging voltage between 13,9-14,4V. The rest voltage of the battery is usually between 12,4-12,5V.