Surf
4
UPDATE
I have played about with things and used a wattage meter on the adaptor.
What I have concluded is that the limit on what the phone and router pulls is 7.7w at the wall and this was using a power adaptor that will push a lot lot more (not a fast charge one though). This charges the phone or at least holds it at the same level of charge.
The Y lead I am unsure if it does anything but I leave it in.
If, as well as tethering the phone, I force the phone to have its screen on at max brightness and not switch off, then the phone drains as the supply can’t keep up. If they switch off it holds its own. So things are on the edge.
If I plug the phone straight into the adaptor to charge it pulls over 10w alone. So the router is the limiting part here. AT 5v 7.5 w means it is drawing 1.5A, this is not a lot.
I did try a “smart” charger that will go a lot higher still but it made no difference, 7.7w was the highest draw.