My car's about 4 and a half years old now and still on the original OEM battery. I have actually been expecting to have to change it for quite a while now, although not because of any problems (car has been starting fine), just that I can tell it's not as healthy as it used to be (starts on second or third turn of the engine instead of the first).
Last night I went to leave my office and the car wouldn't start. The battery had enough charge for all the electricals, but not the starter. So I got the RAC out to jump start it, and we checked the alternator: After only a few minutes of running, the car could start unaided again.
I gave my ageing brain the benefit of the doubt and put it down to leaving my lights on. Yes I know it beeps but I have done it once before!
Last night I checked for DTCs and got:
Address 03: ABS Brakes
1 Fault Found:
01435 - Brake Pressure Sensor 1 (G201)
35-10 - - - Intermittent
Address 17: Instruments
1 Fault Found:
01304 - Radio
49-10 - No Communications - Intermittent
Address 35: Centr. Locks
2 Faults Found:
01367 - Central Locking Pump Run Time Exceeded (Likely Leak)
35-00 - -
01134 - Alarm Horn (H12)
76-10 - Terminal 30 missing - Intermittent
Could these all be triggered by low battery voltage?
So I cleared them and they did not return. I managed to start the car (it had been left for over 2 hours), and I also monitored the voltage for a while with the engine off. It was about 11.9V but not dropping.
So I went to bed thinking that maybe everything was OK.
I was wrong. This morning it wouldn't start. Battery charge worse than before. I called out the RAC who jump started the car again. This time I let the car idle for about half an hour before going off to Kwik-fit. Who tested the battery and said it was fine!
So I'm expecting something more that a dead battery now.
Can't afford to mess around so took it to my local Audi dealer (Reading) and now have it booked in for Thursday (earliest they can do a collection service). They made it clear that I will be charged 65+VAT just for the diagnosis. I have heard both good and bad stories about Reading Audi, but that seems to be typical of dealers these days and I can't keep messing about going to the indie tuners for everything.
I'm not sure what is going to be worse: Paying 65+VAT for them to tell me that I need a new battery, or to find out I have an electrical fault and the whole dash needs to come out...