I have the above and it has started with an intermittent charging fault, some days I get in, start her up and she is fine, no battery light on, volt gauge showing 14+, some days I get in, start her up and the battery light is on straight away and gauge showing 12v and lowers as I drive, sometimes when the light is off and charging fine I can drive 20-30+ miles and all is fine and the light doesn't come on, other times the light comes on after a few miles.
I have run her through VCDS and the only fault codes are an intermittent fault with the coolant temp sensor and no communication with the alarm horn, these have been there since I got the car.
I have removed the battery and charged it up, it is one with the "light" to show you the state of the battery, when I took it off the light was a dim green, once charged it was black, which means the battery is flat and needs charging, re-connected the battery and started her up no problem and the gauge was showing 12v+.
I have tested the voltage at the battery and the alternator, while charging and while not and I am getting the same readings as on the gauge, which I thought I would.
Does this sound like a dead battery, alternator, or something else?
Any help with this would be greatly appreciated.
Thanks in advance
Edit: This is the 180BHP model