Tracking down a battery drain

[Grant Lenahan]

  i rarely see over 50 ma in any of my cars. Look at both parasitic 
drains as well as accessories, some of whcih are, ahem, thirsty

On 9/29/2010 12:55 PM, Joshua Van Tol wrote:
> 450 mA standby current draw is too high, you should be seeing well 
> under 100 mA, preferably less than 30 mA.
>
> A typical car battery has 40-60 Amp hours of capacity. At this rate, 
> the battery will be fully discharged in:
>
> 50/.450 hours = 111 hours = 4.6 days. It'll probably be discharged 
> enough to make it hard to start in about half that time. If you don't 
> drive long enough each time you're out and about to re-charge the 
> battery fully, after a few days to a week, you'll have a dead battery.
>
> 500A is fine. I wouldn't have replaced that battery unless it didn't 
> crank well at cold temperatures.
>
> You're going to need to do the test with the ammeter or test light as 
> others have recommended. An important thing to remember is that if 
> you've got the door open (to access the fuse box) you'll need to tape 
> down the door switch so the dome lights don't come on.
>
> If you don't do this testing and fix the cause of the current draw, 
> you'll be on your way to wrecking this new battery within a few weeks.
>
>
> On Wed, Sep 29, 2010 at 11:22 AM, <TooManyAudis at aol.com 
> <mailto:TooManyAudis at aol.com>> wrote:
>
>     Took the car to Advance Auto last night, had them do a charge on  the
>     battery, then a system test.
>
>     Existing battery (4 years old -- Huw incorrectly guessed at its
>     age being 6
>      years, resulting in 4 demerits) was putting out 500 +/- amps, with it
>     being  rated for 700 amps new.
>
>     Put in a new battery for $100.  Rated at 850 amps with 700 cold
>      cranking
>     amps.  Started strong this morning.
>
>     The salesman at Advance did a charging system test after the
>     install of the
>      new battery.  Results are:
>
>     1)  Battery:  12.56v; measured at 817 CCA, rated at 700  CCA;
>      Temp:  79
>     degrees f.;  Good Battery
>
>     2)  Starter Test:  Voltage:  10.99v;  Amps:   215.8A;  Time: 1.03
>     seconds;
>     Cranking Normal.
>
>     3)  Charging System Test:  No load:  14.00v, 4.4A;   Loaded:
>      13.47v 2.4A:
>     No Problems
>
>     4)  Drain Test:  0.45A:  Pass
>
>     With # 3, my Instrument cluster voltmeter showed right around 12v
>     with  the
>     high beams on and AC on max during this test.  Is there an
>     explanation  for
>     the difference.  Is the IC voltmeter picking up voltage after the
>      radiator
>     fan, blower fan and compressor clutch?
>
>     Also, with #4, is 0.45A too high?
>
>     Thanks for the help.
>
>     Tom
>     Charleston, SC
>
>     1995 A6q  5-speed (up for interesting offers) 249k
>     1988 80q (sold, and still going  strong!) 250k+
>     1991 200q20v towed away in the middle of the night by a VW  diesel
>     pickup
>     275k+
>     1985 4kq a freakin' beast of a car! 275k+ and presumably  still going
>     1987 4k died in a hit and run 250k+
>     1983 4k Very first Audi 35  to 38 mpg.  Victim of crank key
>     failure 300k+
>
>
>     In a message dated 9/29/2010 9:29:32 A.M. Eastern Daylight Time,
>     glenahan at vfemail.net <mailto:glenahan at vfemail.net> writes:
>
>     so why  guess? Measure the idle draw,and load test the battery.
>     20:1 its
>     the battery.  6 yrs is 2 beyond its shelf life.
>
>     Grant
>     On Sep 28, 2010, at 4:14 PM,  Steve Buchholz wrote:
>
>     > I'm with Huw ... the voltage you're seeing  should be enough to
>     crank ...
>     likely high internal resistance in the battery  is the problem.
>     >
>     > I'd also allow a bit higher battery draw with  everything off
>     ... 10mA is
>     too low IMO, I wouldn't worry until the current got  up into th
>     100mA range
>     ...
>     >
>     > Steven Buchholz (mobile)
>     >
>
>
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