Hey there! It sounds like you might be facing a couple of potential issues with your Siemens PSC-12. Firstly, make sure the AC power source is working properly and that there are no issues with the connection. Check the input voltage to ensure it’s within the specified range. Secondly, inspect the batteries themselves and the connections to ensure they’re in good condition and properly connected. If everything seems fine there, it could be a problem with the charger circuitry or the battery charging algorithm. In that case, it might be best to reach out to Siemens technical support for further assistance or consider contacting a qualified technician to diagnose and repair the unit.