USB Ports Poor Charging?
 

The two USB ports in the center armrest on our 2015 S550 takes FOREVER to charge my Samsung Galaxy S5.

We are using the cable that came with the car.

It charges at less than 1% every 30 minutes or so. Barely anything.

I can plug in a cig lighter charger and charger WAY faster than that.

I have the same problem. I know the Samsungs are finicky when it comes to charging, but the USB in the car does virtually nothing.

I have an iPhone and I have no trouble at all charging it on the USB port. It charges quite fast. I am using my own cable, however, since the car did not come with the correct cable to fit my iPhone 5.

I was charging my portable blender in there; worked great!

X2

According to the USB protocol, if the device needs a lot of power, it needs to ask the USB source what it wants and the source supplies this current if it can. Perhaps the Samsung product fails to negotiate sufficient charging current from the car?

Rear armrest USB won't charge my iPhone but it does work on other iPhones. Cigarette lighter works to charge my iPhone.

I have same problem with Motorola phone. It won't charge when fully drained. Cig adapter works just fine. So you guess that phone should say somehow it needs more charge is totally wrong, because my phone has no idea how it is connected to USB using cig adapter or directly. I guess USB port just complies with USB specification giving 500mA, when cig adapter works in charge mode giving up to 5A, see here. Perhaps next year S will get USB 3.1, so we will get our phones charged much faster.

Works fine with iphone, Have you tried a different usb slot ? Theres always one that provides more power than the other.

USB Poor Charging
 

Just wanted to add my own frustration here.

I own a 2015 S550 as well (original post). And up until a month ago, the two USB ports in the console did a great job of charging both my Samsung Galaxy phone and my wife's iPhone while connected and in use. Now, neither port will sufficiently charge either brand. Even with the phones turned off, the charging is so minimal as to barely move a single percentage point in a few hours. So it's rather strange that all of a sudden, this has become an issue.

Not sure what would drive the ports to no longer charge the way they were. Cig lighter charges just fine, but keeping that open prevents the front cup holders from being utilized, so not a great long term solution.

Any insights on the possible change and/or solution?

Quick way to up the Amps.... 2x the power at the connection. :)