USB-C is garbage. I had many times this happening, even with flagship phones with the cable supplied, and it either shows 'charging slowly' and gives extremely long times, or worse, the percentage drops after it climbs a bit, but phone continues to show that it 'charging'. If I don't catch it, I wake up to either a completely dead phone, or it having charge around 18% or less, only then it shows 'charging slowly, unknown time remaining'.
It's a USB-C thing. We were fine with Micro USB, nobody asked for it to needlessly change. If your phone supports wireless charging, I suggest using that, as that's what I do. I'm sick of plugging things in twice for it to even start charging, and hate it most when it fakes me out and is dead the next day. I never had any issues charging my Galaxy S4. Or HTC Thunderbolt. Or any other Micro USB device.
You can chase the issue and waste a lot of money on third-party USB-C cables and fail like I did, or use wireless charging. I find the latter more reliable. I am convinced that USB-C is what is making my Android Auto bug out and think there is no signal when there is as well.
