Since you say that at some times you get charging going, I would first check if you have good connection of wires to your lighter socket.
Second, if wires are ok, then it might be that your USB adapter will not start charging below some voltage treshold (if you are on motorway, your voltage can raise a little).
These are two things that came to my mind when reading your post.
However, instead on investing to possibly another USB adapter, powerbank would be better choice.
Second, if wires are ok, then it might be that your USB adapter will not start charging below some voltage treshold (if you are on motorway, your voltage can raise a little).
These are two things that came to my mind when reading your post.
However, instead on investing to possibly another USB adapter, powerbank would be better choice.