Bowtie84

Hello,

Been turning wrenches since I was 12, 32 now. Tuned up a 90 Ealge Talon TSi from it's stock 190 fly wheel hp to 340whp, so I have some idea of what I'm doing.. anyway. My wife went to start her car the other morning and the battery was to low on charge to start, when she tried the dash lights and relays all freak out. Okay grab the battery charger, yep it was down to like 30%...that's odd but I figure maybe it's a fluke, light was left on, door wasn't fully closed, usb cord/device was pulling on it for a few days (she doesn't drive a lot) etc. charge it and go to bed, next day same thing. Crap... I immediately figure it's probably a bad diode in the alternators rectifier or something but it was late so I put it back on the charger and checked when I got home, started the car, grabbed the multi-meter and switched to 0-20v A/C, checked the battery, 0.0v A/C okay so it's not a bad diode in the alternator, just to be sure I switched to D/C yep 14.2v.. so I started checking the fuse box under the hood, most I found was the circuit for the ECM was still active for a few minutes after I shut down the engine and removed the key at 3 tenths of a volt, which shut down 10-15min later. Didn't find but I think one other at a tenth of a volt.. okay so check the interior box, pull the panel on the passenger side floor well and start probing away, most I found was .54ish volts but seeing as the door was open that may have been it. I can't recall if I had turned off the interior lights or not (that come on when doors are opened) I think I did..

If that circuit stayed active is half a volt (unknwon amperage) likely to drain the battery in 12-16hr's to 1/3 capacity? Is there something else I should check?

Bowtie84

Disconnected battery, removed, checked case. Case looks fine, no visible damage. GO
Charged battery, checked battery, no real voltage drop. GO
Checked terminals, solid connections, clean with no corrosion. GO
Performed parasitic drain test, initially see's 2.3amp but within 30sec falls to 2 amps, then 1.5 then .75 then 0.01 amp on and off, I don't have a scale low enough to see below 1 hundredths of an amp. ? Need to figure out how to use smaller scales.
Took for a test drive, everything is normal, parked, waited a few minutes took a reading of 12.85v, going to re-check in half an hour.
*update* After half hour voltage checked 12.89

Bowtie84

Took the car to parts store, load test said the battery was only showing 230cc amps. ugh, yeah that's not accurate. So replaced with a new AGM battery, time will now tell if it cause was actually a bad cell in the old one.

P.S. Holy crap have batteries gotten expensive!

blstaten

Any updates Bowtie? I replaced my battery a couple months ago when it wouldn't start after work and the battery light came on yesterday before the Captiva lost power and died on the way home. I am told it is likely the alternator but reading about other electrical problems with these cars makes me hesitant to have it replaced for $700-800.

Bowtie84

Turned out to be the battery. $170 new unit (opted for a AGM unit instead of lead acid) from Advance and no drain problems sense. The other battery had one or more cells short out/go bad.