My portable charger is an INIU BI-B6, and its output is listed as 4.5V at 5A, 9V at 2A, or 12V at 1.5A. I'm not sure how to interpret those ratings, and I'm worried they might damage my Samsung Galaxy S21 or the charging cables. I've already had problems with my phone's charging port, so I'm feeling especially cautious. Are these specifications safe for the phone, and how does the charger decide which output to use?
2 Answers
Those are the maximum output modes the power bank supports. The phone and charger communicate through the charging standard and select a compatible voltage; the power bank does not simply force 12V into the phone. As long as the charger and cable are in good condition and the phone supports the negotiated mode, these ratings should not damage your Galaxy S21 or the cable.
I’ve used the same power bank with both a Galaxy S7 and a Galaxy S21 for years, using the same cables, and haven’t had any problems. A damaged or dirty charging port, a worn cable, moisture, or a loose connection is more likely to cause charging trouble than the power bank’s normal output ratings. Checking the port and replacing suspect cables would be a good first step.

So the listed specifications shouldn’t hurt either the phone or the charger? I’ve been extra paranoid because my charging port has caused problems before.