Battery drain issue solved!

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smeats
Posts: 13
Joined: Thu Aug 17, 2017 6:48 pm
Location: Scotland

Battery drain issue solved!

Post by smeats »

I like to use my 6er as often as possible but with the bad weather it will either be on my drive for a few days or when the weather gets worse, stored in a lockup to protect it from the elements.

Anyway, after not using it for 4 or 5 days a nice day came along and I was going to drive my 6er to work but it was as dead as a dodo! After work I put it on charge and it was down to 9.5 volts! I left it overnight and it recharged to 12.6 volts, good! As the battery is less than a year old!

That evening (after looking at all the advice in these pages) I went to see my friend and mechanic to check things with his multimeter to see if my alternator /voltage regulator was putting out enough of a charge. Well everything read OK at 13.8v with engine running. Next with the engine off and keys out he set it to amps to see how much of drain there was, it read 300ma!

I thought we would have to go through the process of pulling each fuse to find the offending circuit the try and trace the fault but my friend disconnected the battery positive and touched it on and off repeatedly. I asked what he was doing and he asked if I could hear a relay clicking from the fuse box! I had the cover in my hand and from the handy layout guide l identified it as the fog light relay! I removed it and my friend put his meter back across the now connected battery and zero!

The fog light relay is now sitting in the glove box and won't be put back until MOT time! I left the car for almost a week and it started with a roar with the first turn of the key!

I thought as this is a common topic I'd share incase my friend has made some kind of great discovery or this has been a total fluke! \:D/

All thoughts and opinions welcomed!
1981 635CSI series 1
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Brucey
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Joined: Fri Apr 09, 2004 7:17 am
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Re: Battery drain issue solved!

Post by Brucey »

series 1 cars have a different set of problems; series 2 cars usually have a ~60mA parasitic drain from the circuit that charges the SI batteries.

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~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
smeats
Posts: 13
Joined: Thu Aug 17, 2017 6:48 pm
Location: Scotland

Re: Battery drain issue solved!

Post by smeats »

Ah! That makes sense Brucey. Trust the series 1 to be different! I suppose later cars have extra equipment that takes a small charge all of the time, I'm just very pleased that my problem cost nothing and took about 10 minutes to fix!

The fog light relay being in the on position all the time is a bit strange isn't it? :-k
1981 635CSI series 1
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