2005 Renault Scenic flat battery and check emissions light on

My Problem is that a few months back the check emissions light came on in the dash and soon after this every now and again the battery would be flat in the morning. took it to an autosparks who suggested it was a faulty battery, bought a new battery had faults cleared, a few days later faults appeared again and battery died again!took it back to the garage who kept it for a week cleared the faults and it started fine every time, took it home and same problem reoccurred, got them to come out, ran a diagnostics check and found no fault with battery, alternator or camshaft. However same thing happened again, took it to a renault dealership who couldnt have been less helpfull and am now left with a car that wont start without a jump, had a look on other forums and the same problems are happening a lot, is there a common cause? could it be camshaft sensor? or TDC Sensor? please help.