Battery Drain
07-18-2018, 07:11 AM
#1
AudiWorld Junior Member
Thread Starter
Battery Drain
Hi, I have a 2008 3.0 TDI that has developed a battery drain. Three mornings in the last week it has left me down, with enough power to crank the engine but not enough to start it. Each time charging the battery enough has got the car started, and after that it has started every time until the next time it lets me down. I charged the battery fully and under cranking I saw voltage go as low as 9. I took this result to be normal for a functioning battery, is this correct?
I tried seeing what the draw off the battery was at rest and got a reading of 6A but thought my result must be skewed with the boot lid being open?
I tried seeing what the draw off the battery was at rest and got a reading of 6A but thought my result must be skewed with the boot lid being open?
07-18-2018, 08:39 AM
#2
AudiWorld Super User
Why isn't the answer a bad battery rather than a battery drain?
As in, they last as little as 3-5 years, and seldom go more than 7-9. Typical symptom as they fall off the death knell cliff is they can't hold charge. Yours should be on at least second battery by now. Thus, age and history of current battery?
As in, they last as little as 3-5 years, and seldom go more than 7-9. Typical symptom as they fall off the death knell cliff is they can't hold charge. Yours should be on at least second battery by now. Thus, age and history of current battery?
07-18-2018, 11:16 AM
#3
AudiWorld Junior Member
Thread Starter
Why isn't the answer a bad battery rather than a battery drain?
As in, they last as little as 3-5 years, and seldom go more than 7-9. Typical symptom as they fall off the death knell cliff is they can't hold charge. Yours should be on at least second battery by now. Thus, age and history of current battery?
As in, they last as little as 3-5 years, and seldom go more than 7-9. Typical symptom as they fall off the death knell cliff is they can't hold charge. Yours should be on at least second battery by now. Thus, age and history of current battery?
07-18-2018, 03:02 PM
#5
AudiWorld Junior Member
Thread Starter
Care to elaborate? When the car has all doors locked and the boot lid open but plungers taped down the car will stay awake, is that what you're saying?
07-18-2018, 04:50 PM
#6
AudiWorld Super User
Honestly, waste of time if you don't even know age of battery but circumstantially it would likely be dated. It's summer too in Northern Hemisphere; come winter no fun when cold dead of night one gets left high and dry. Second time a battery craps out on me on an unexplained basis (i.e not my stupidly leaving lights on, using VCDS with ignition on for hours, etc.) and more than 4 or 5 years old, summarily replaced.
As Mister Bally said, a lot more to testing drain than taping a switch. What's the plan for alarm system, suspension periodic compressor run to true up ride height, and various other things? You monitor it if serious with VCDS or similar tools...which cost more than the lowly battery. The store test would be a load one, and battery places will often do that for free. Or if it is fried, another possible is charge it up disconnected from car. Then read voltage. Let it sit and read it again the next day. If it is heading south, you will llikely see a meaningful drop just sitting there. Or if it doesn't even show close to 13 volts right off the charger, it is also probably already toast in at least one cell bank.
As Mister Bally said, a lot more to testing drain than taping a switch. What's the plan for alarm system, suspension periodic compressor run to true up ride height, and various other things? You monitor it if serious with VCDS or similar tools...which cost more than the lowly battery. The store test would be a load one, and battery places will often do that for free. Or if it is fried, another possible is charge it up disconnected from car. Then read voltage. Let it sit and read it again the next day. If it is heading south, you will llikely see a meaningful drop just sitting there. Or if it doesn't even show close to 13 volts right off the charger, it is also probably already toast in at least one cell bank.
Last edited by MP4.2+6.0; 07-18-2018 at 04:57 PM.
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07-19-2018, 05:28 PM
#9
AudiWorld Member
Disconnect negative overnight and see if you still have low voltage the next morning. Battery management system would typically shut off all but the critical stuff when voltage get's low.
07-20-2018, 03:33 AM
#10
AudiWorld Junior Member
Thread Starter
Thanks for all the replies. I ended up replacing the battery with an AGM 90Ah 900CCA one I took out of a 1 series BMW, and the A8 has been starting every time without fail since - so it's looking like the original battery is bad. I say this, although this morning with the new battery, the keyless entry didn't work and when I came to a stop, the stop button killed the engine but wouldn't turn off the ignition or apply the steering lock which I then had to do by turning the key - oh the hardship! I've since been thinking might this be the battery management at work seeing as I didn't code in the current battery? Or do I have another problem? - Add this to the fact that I have an amber adaptive suspension dash light on all the time - this car is sure keeping me entertained! I have an OBDEleven dongle arriving any day now so there's not a lot I can do as regards coding of battery until that arrives which gives me time to shop for a new battery. Can someone tell me if this would be a suitable replacement? I've searched online and don't see them mentioned in the same breath as A8s so I have my doubts. The batteries I see being used in all the coding videos seem to be Varta.
I also have been looking at this and this.
I also have been looking at this and this.
