Befuddled Battery?

[Driver8]

Hi all - I'm having an issue with the battery on my 2004 3.0i and I'm looking for advice and/or confirmation of my conclusions.

Problem: Car occasionally will start after sitting for a few days.

Symptoms: Lights come on and steering wheel/idiot lights/V-1 all do their thing, but there is not enough power to turn the starter. The solenoid clicks a few times but nothing more. A nice slow trickle charge revives the battery and keeps it alive as long as I drive the car every day or so. The problem got worse, though, and I replaced the battery with a NAPA-spec Exide 72-month battery. The problem reasserted itself yesterday after having the new battery installed for about two weeks. I installed it myself. Everything was done right and by the book. I have pretty much eliminated the battery itself as the source of the problem.

Potential Sources of Problem:

1) Undersized battery - Not likely, as it was one of two battery sizes listed for the X, both of which should be more than adequate. The case size is smaller than the OEM battery, but otherwise this should not be the source of the problem.

2) V-1 hookup - Not likely. It's attached to a switched power feed and goes out with the ignition.

3) BTUM - Not sure if this is powered full-time or not. I need to check the indicator light to see if it shows when ignition is off. Even if it stays on, honestly, how much power would a tiny blue LED indicator light draw?

4) Final Stage Resistor - Likely. I researched the issue earlier and this could be the culprit. While I cannot honestly say I've noticed the fan running with the ignition off, I can't say that I haven't, either.

5) Other Closed Circuit Issue - Possible. This one is beyond my abilities and since the X is still under warranty, I'd leave this one to the experts.

6) Alternator - Possible, but not likely. Assuming I drive the X every day, the battery will stay charged, a direct correlation between a good alternator and a battery that is being discharged when the ignition is off. Plus, I think a bad alternator would clearly manifest itself by allowing the battery to die while driving, but I could be wrong on that.

At this point, I think I have realistically eliminated all the DIY stuff that could be draining the battery. New battery. No V-1 lights when ignition is off. I'll double check the BTUM later today. I think it's a FSR or something not shutting off with the ignition. Any thoughts/comments/advice greatly appreciated!

Mike

[Zulu95]

If the total current draw exceeds 38 ma then ALL the electronics do not go to sleep. (LED is around 20 ma.) All the modules staying on will soon pull down the battery.

[Driver8]

Okay...I checked the BTUM over lunch and as I expected, the LED light was not on, so I think it's safe to eliminate that as a cause of the problem. Last thing I want to double check is the hardwired V-1 tap to make sure there's nothing closing the circuit there, otherwise I'm officially out of ideas. Thanks again to all.

Mike

[Zulu95]

You will need to check your X from outside without touching, arming/disarming or opening anything tro do this check: See if the LED on the shift lever goes out after abour 30 minutes. IF it stays on then the sleep mode is not cutting in and you get battery drained problems. If you are still covered by warranty then let the dealer check why but be advised they can & will blame after market retro fits such as your V1 and will charge you. So disconnect anything non OEM before you take it in. Modules can and will go bad and these can be the source of the problem.

[Driver8]

Zulu - Good tip. I'll check it out tonight when I get home. THANKS!

[Driver8]

Ok...I checked the shifter LED and noticed it stays on for some time after the last door closing. The LED next to the phone indicator stays lit as well. Both go out within the 30 minute timeframe you mentioned. I think I could rule this one out.

One other note, I have gotten no indication of a problem with the charging system on the dash. No idiot light or anything...just the lighted "4x4 exclamation" light that goes out after a dead battery sequence.

Thanks - Mike

[Zulu95]

You need to connect a volt meter and see if you get around 13.75 V or so when the engine is running. The idiot light is quite dumb as it really only indicates full failure but not low charge rates.
FYI There is an article in a recent Roundel that tells how to up the charge of Bosch altenators by fitting a diode in the sense circuit as they tend to charge at a lower voltage than others. My Explorer shows 14.5V constant and the first battery failure was 8 years into ownership. The X seems to hold nearer to 13.85V and I had to fit the second replacement battery just after I bought it at 2 years old! (First replacement was for a VW fitted by dealer to sell it!)

[Driver8]

I've driven it all day today with numerous startups. Nothing out of the ordinary. No dragging starter. No error messages. No reboots. It's around 75 degrees and sunny. Moderate humidity. There's got to be a drain on that battery somewhere post-shutdown that's dragging it down. I'll keep looking. Thanks!

Mike

[Driver8]

Hmmmmmmmmmm...interesting development last evening.

I started the X up to go home from work and the starter seemed a little slow. I got home, shut her down and restarted...even slower. The third restart wouldn't turn the starter over, it just did the click click click thing.

I now think my problem is in the charging system since I drove a fair amount yesterday and it would have stayed well-charged, assuming the alternator is fine and using a new battery. I guess it could be a combination small drain/low alternator output, but knowing the battery is new and had just come off a 36 hour trickle charge, it sure did drain down in a very short time.

Time to call the dealership, I guess.

Mike

[vinuneuro]

I'd bet on a bad alternator or starter solenoid.