Charging issue with S8 and S8+

[Android Central Question]

Hi, me and my wife both has S8 and S8 plus and we bought a car usb charger from amazon to charge our phones and we have being using this over a year with out a problem but from past 1 - 2 months whenever we plug our phones to charge its shows as if its charging but eventually instead of charging its taking off the charge even though we just leave our phones without using. i thought it may be the car and we tried in our 2nd car and its the same thing. then i thought it may be cable so i tried with the original charger cable which came with phones and tried but unfortunately its the same. but if i take the same charger and try to charge my phone inside my home its charges perfectly. so what i m able to understand is, is it the problem with phone or cable or car?

 

[B. Diddy]

Welcome to Android Central! Do you see a lightning bolt in the battery icon in the status bar when it's plugged into the car charger? If you don't, is this only when Android Auto is running?