[Galaxy S 4 Q&A, Help & Troubleshooting] Clovett:
Ok so this is one possibility. I posted something similar then emailed Samsung. I'll post what they replied also

I just got this S4 with water damage to repair and use. Because of so many people having charging port issues I made sure to check it thoroughly. What I found was that, by pinout, it appears two of my connections are not soldered correctly. Further from what I can tell one of them is the +5v input. I had a lot of trouble finding a pinout and don't know if what I found is correct. This would account not only for the higher current draw on the phone but also for the melted ports. I also sent the pics to Samsung to which they sent this in reply. My issue is they can clearly see that it's not soldered correctly and still take the stand that I might be paying for the repair. And of course they won't repair it regardless as I bought it second hand.

How many of these could be out there half soldered??? I have pics if anyone wants to see them.

Thank you for contacting Samsung Telecommunications America.

After reading your e-mail we understand that the charging port of your phone is partially soldered.

We sincerely apologize for the inconvenience caused.

As you are experiencing issue with the charging port, the device needs to be physically examined and serviced by Samsung technicians. Please send the device to Samsung service center to get it fixed. You can optout for any of the below options to send the device in to service.

(a).You may wish to contact your carrier for any service options.

(b).You can also contact your insurance provider to know the service options under insurance coverage if the device is insured.(OR)

(c).Send in to Samsung for repair by filling out a Return Materials Authorization request(RMA).Our voice support team can be reached out at the toll free number 1-888-987-4357, Mon-Fri: 7 AM - 9 PM (CST), Sat: 9 AM - 6 PM (CST).

You will get a shipping label in your e-mail address once they file a service request. The link for the e-label will be active for up to 10 days, after the 10 days the link will expire and the you will then need to call back in to have the e-label resent. Please send the device within 3 days of being sent the e-label.

We will bring the handset in for evaluation, and the repair technician will determine if the cause of damage is due to defect or an external source. If a defect is found due to external source, you will receive an email with the option to pay for repair. If the damage is not caused by external source, the device will be repaired In-Warranty.

It will take 2 business days to ship in and 2 business days to ship out the device. It requires 5-7 business days to fix the issue once our technicians received the device at our service center.

We once again sincerely apologize for not being able to assist you.

Do you have more questions regarding your Samsung Mobile Phone? For 24 hour information and assistance, we offer our new FAQ/ARS System - Automated Response System at http://www.samsung.com/support. It's like having your very own personal Samsung Technician at your fingertips.

Thank you for your continued interest in Samsung products.