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Old 29th October 2017, 12:34 AM
27litres's Avatar
27litres 27litres is offline
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Default Parasitic Power Drain finally resolved!

I've owned my S8 since Feb 2013.

Ever since I've owned it it's had a parasitic power drain.
The previous owner hadn't been driving it much and didn't recognise it for what it was, blaming a dead battery and replacing it and resolving to drive it more just prior to putting it on the market.

Once in my care, the power drain was simply an inconvenience as I went about catching up on a lot of deferred maintenance (don't worry, I paid accordingly!).
When I got around to it, i bought a new battery (despite reputedly only being replaced about 5-6 months previously).
4 or 5 days later it then went flat and thus started the repetitive cycle of charging the car every couple of days to prevent being caught out.

I noted that it seemed to go flat regardless of how much or how little it was driven, so checked the alternator using the voltage over the terminals method - 12.4 volts static battery power, 13.6 volts running with headlights, radio, a/c etc all on. Could be better, but appeared acceptable.

So I did a brief fuse check using the multimeter in amps in series with the +ve lead and pulling fuses. This was done after allowing the car to shut down over a 10 minute period having fooled the car into thinking it was locked by running a screwdriver through the boot and drivers door locks.
Didn't find any circuit showing any significant change to amps.

That left maybe a faulty relay (though most of those still run via fuses) or some faulty or non factory wiring. Or I was missing something!

At this point life got in the way (I moved and then my daughter was born) and I simply tolerated the inconvenience of the power drain by charging the car every couple of days, and carrying the LiPo jump pack (which did get used a few times!).

I did some Google and forum searches and came across a post where someone had found the phone circuit was staying constantly live. So I pulled the phone fuse and left it out (really must remove that clunky old thing one of these days...). Didn't fix it.
Another post revealed that when the voltage regulator on the alternator starts to break down, it can become it's own power drain which is undetectable by standard fuse pulling methods. This made sense to me due to the consistency of the drain (no matter how much or little it's driven).

I accumulated a new regulator, new slip ring, and new bearings and eventually delivered all these parts with my removed alternator to my local auto elec (well not so local these days, but I've been using him for 15 years or more).
He reckoned the alternator tested fine, but followed my instructions anyway...

Put it all back together and guess what!

The battery went flat again...
****.

Well, back on the charger. Daily now though, and engine turning over slowly... Hmm... I wonder...
About two weeks later, the battery failed completely.

I dug out the original battery from the mess in the garage and chucked it back in the car.

We're at 7 weeks now, and I haven't charged it yet!
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Cheers

Marty


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Current:
2001 Audi S8 - Brilliant Black with Black interior, C5 RS6 rims (whenever I actually put them on...), Solar Sunroof, Tinted side and rear glass, RNS-D, XCarLink, Bose, clunky old phone in arm rest!
2002 Audi S8 - Project
Replacement head coming arrived thanks to MJ
Silver with Black interior. All features as the '01, with the 'S' mode auto shifter. Dodgey rear tint (need to find a way to get rid of that).
Family:
2009 Volvo XC90 V8 R Design
- has a louder more obnoxious exhaust than the S8, sounds great! Love this thing - Q7 was double the price, and certainly not double the car!

Sold:
1997 Audi A4
- Hamilton's Club Sport, Achat Grey (will miss the old girl)
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  #2  
Old 29th October 2017, 12:38 AM
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27litres 27litres is offline
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Default

Conclusion:

Very long winded I know, but I think it was the alternator all along. Just took a long time to convince myself and get to it.

You have no idea how much less of a hassle it is to not have to charge the bloody thing all the time!

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Cheers

Marty


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Current:
2001 Audi S8 - Brilliant Black with Black interior, C5 RS6 rims (whenever I actually put them on...), Solar Sunroof, Tinted side and rear glass, RNS-D, XCarLink, Bose, clunky old phone in arm rest!
2002 Audi S8 - Project
Replacement head coming arrived thanks to MJ
Silver with Black interior. All features as the '01, with the 'S' mode auto shifter. Dodgey rear tint (need to find a way to get rid of that).
Family:
2009 Volvo XC90 V8 R Design
- has a louder more obnoxious exhaust than the S8, sounds great! Love this thing - Q7 was double the price, and certainly not double the car!

Sold:
1997 Audi A4
- Hamilton's Club Sport, Achat Grey (will miss the old girl)
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  #3  
Old 29th October 2017, 01:28 PM
David's8's Avatar
David's8 David's8 is offline
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Glad you got to the bottom of it in the end. So, the battery you bought was eventually bu@@ered by all the going flat/re-charging that was going on?
Its difficult when one fault is masked or occurs in parallel with another.
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2002 D2 S8 Ming Blue, Valcona leather, Vavona wood insert, solar sunroof (to be fitted), Heated rear seats, extended leather pack, 18 Avus, ski hatch, Bose, auto dim rear view mirror, rear blind.

Last edited by David's8; 2nd November 2017 at 03:12 PM. Reason: typo
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  #4  
Old 1st November 2017, 11:44 AM
27litres's Avatar
27litres 27litres is offline
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I just got into a recharging routine.
In fact I used to get a stress similar to range anxiety whenever anyone wanted to borrow my smart charger or I had to leave the car anywhere!
I carried the charger in the boot all the time (rarely detached from the battery!), as well as a LiPo jump pack!

It was a bit of an effort to not charge it after the battery swap!
__________________
Cheers

Marty


____________________
Current:
2001 Audi S8 - Brilliant Black with Black interior, C5 RS6 rims (whenever I actually put them on...), Solar Sunroof, Tinted side and rear glass, RNS-D, XCarLink, Bose, clunky old phone in arm rest!
2002 Audi S8 - Project
Replacement head coming arrived thanks to MJ
Silver with Black interior. All features as the '01, with the 'S' mode auto shifter. Dodgey rear tint (need to find a way to get rid of that).
Family:
2009 Volvo XC90 V8 R Design
- has a louder more obnoxious exhaust than the S8, sounds great! Love this thing - Q7 was double the price, and certainly not double the car!

Sold:
1997 Audi A4
- Hamilton's Club Sport, Achat Grey (will miss the old girl)
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  #5  
Old 1st November 2017, 12:38 PM
awolfinsheepsclothes awolfinsheepsclothes is online now
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Location: oldham
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Well at least you got there in the end, well done
Dave
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2002 S8 silver with black half leather
2000 d2 S8 in Racing green pearl, RS4 manual gearbox,
2003 A4 avant TDi
1997 Volvo V40 2.0T
1992 Mazda eunos v spec
1976 Reliant Kitten
1965 Porsche 911
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