Therefore, I decided to connect an amp meter to the charger and measure the current draw:
2.1A car charger - USB input - current draw: 0.8A to 1A with the screen on and Waze running with GPS on
1.5A Sony mains charger - USB input - current draw same as above
This means that the phone does not draw enough current to keep the battery charged. OS problem ?
I tested even the dock charger and I got a very different result:
1.8A dock charger - Dock charger side pads - current draw 1.4A with the screen on.
Why the sudden increase in current when using the dock charger ? Is there a fast charge mode for the Xperia Z ?