I have a 2015 titanium estate 1.6 diesel ( new shape), and it has recently suffered from a dead battery after a week of non use. It was recharged and checked at 100% 12.7v, after 12 hours of non use it was checked again and was at 90% and dropped further to 60%. I recharged again and disconnected from the car and after 12 hours had dropped to 90%, indicating a failing battery. A new one has been installed and is also showing a 90% after 12 hours and 70% after 24 hours, so I am now thinking that something is not turning off causing parasitic battery drain.

Additionally when the engine is turned off, there is a buzzing  noise for about 1 minute from the centre rear of the engine bay, a friend has a similar car and his also does it but only for about 10 seconds, 

Does anyone has any suggestions

 

Disconect the cable to batterisensor, look at batteri - a black cable what happens after that ? It whort to test that