after 90 mins of driving the engine warning came on follow by HDC / brake warning lights and transmission failure- shortly followed by the car going in to slow drive mode. i just got home then the car stopped turns out battery voltage down to a reading of 7v connected but 11.5 when standing off the car. fully recharged and the car goes fine and alternator appears to be working. ran diagnostics using a basic plug in - no warnings accept low voyage to immobiliser. i am worried it will go again - anyone have any ideas what this is - i have installed a new battery and earth connection incase but cannot think what else to do..