My battery volts keep going low

What is your question?

I have a 2007 Cadillac DTS that I just replaced the alternator and battery which are both brand new because the volts kept going down til it died on me... Now that I have a new battery and new alternator 1 day ago and my volts are going down again... What can it be now? Also there's a sound coming from under the hood a loud squeaking sound

How long has your 2007 Cadillac DTS had this problem?

2 days