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Voltage while car off? parasitic draw?

josh72ooh2

By josh72ooh2,
in BMW 2002 and other '02

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Hans Grand Master

Hans

Posted
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I'd be trying to isolate the issue: assuming the battery is getting charges while running (14v), is the battery losing its charge, or is there a parasitic draw. I'd disconnect the battery and take voltage readings over  a few days.If it drops, battery is the culprit. How old is it?  If voltage holds, reconnect the battery and do the same thing. If voltage is now dropping, connect ammeter between ground post and cable and look for amp draw. 

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TobyB Grand Master

TobyB

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Oh, good point- it's quite possible for a battery to develop relatively low internal resistance in one or more cells, then self- discharge.

 

BUT I betcha, given the pretty custom nature of this car, that something else is going on.

Like the dome light circuit from the donor's on... ;)

(yes, the '71 race car still has its dome light circuit.  It's even labelled)

 

My take is it's just going to be a measuring game.  Using the ammeter in mA mode, and maybe even watching it over time

(yes, you can data log, or just point your video camera in time- lapse mode at it).

 

t

 

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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josh72ooh2 Veteran

josh72ooh2

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I just went out to check the car and it isn't reading any draw at all... so now i'm totally scratching my head. I'm leaving the battery disconnected until i can figure this out and i'll just connect it when i want to drive the car (about every week or two).

1972 Malaga (according to DMV) 2002. (Manufactured in '71)

http://www.beemersandbits.com

'77 BMW R100S '73 BMW Cafe bike  1966 Triumph T100C  1966 R90/2 BMW Sidecar Rig  1956 MV Agusta Turismo Rapido

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RAS-2002 Experienced

RAS-2002

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Why not just get one of these: (or one like it)

http://www.eastwood.com/battery-shutoff-switch-w-instructions.html?fee=7&fep=465&SRCCODE=PLA00020&product_id=25053&adpos=1o4&creative=83580267780&device=c&matchtype=&network=g&gclid=CPHqouT4itACFYwDhgod2akPWA

It'll save you the hassle of dealing with removing the cables from the battery terminals...

-Bob

 

-Bob
(current: 1972 Malaga 2002, VIN 2584644, build date July 26, 1972)

 

Previous: 1973 Sahara 2002 #2585896 (RIP), 1969 1600, 1971 2002, 1964 Triumph Herald convertible, 1965 Triumph Herald convertible, 1961 Triumph TR3A, 1967 Triumph TR4A-irs, 1959 Austin Healey 100/6, and about 10 other cars (most of which were quite boring)...

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josh72ooh2 Veteran

josh72ooh2

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Why??? because i never knew those existed!   Seems like a good band-aid solution for now.  I'll look into getting one asap. 

Thanks!

-josh

1972 Malaga (according to DMV) 2002. (Manufactured in '71)

http://www.beemersandbits.com

'77 BMW R100S '73 BMW Cafe bike  1966 Triumph T100C  1966 R90/2 BMW Sidecar Rig  1956 MV Agusta Turismo Rapido

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josh72ooh2 Veteran

josh72ooh2

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8 minutes ago, Hans said:

Did you test the battery for voltage drop while disconnected?

Yes, it was around 12.56V (if memory serves).

1972 Malaga (according to DMV) 2002. (Manufactured in '71)

http://www.beemersandbits.com

'77 BMW R100S '73 BMW Cafe bike  1966 Triumph T100C  1966 R90/2 BMW Sidecar Rig  1956 MV Agusta Turismo Rapido

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