from previous experience on my old car the volateg regulator causes the problem that you just described. I changed out my alternator twice and once with an expensive performance alternator and both got messed up as the volatge regulator was the problem... so just a heads up

 

Thanks Kook_yaar. I think that is probably it. doesn't seem right that the alternator hit 14.5V and just gradually meanders down over the course of 3-4 minutes to 13V and stays there. Quite honestly, I've spent too much time at the dealer and hope that the voltage regulator is a simple fix.

 

I read the charging section in the factory service manual. Apparently, it is not unusual for the voltage to drop to 12-13.5V after it senses the battery draw is diminished (ie. charged). It accomplishes that by a battery current sensor on the battery ground cable.

My latest problem with the battery being 11.2V was probably due to my playing around with my Escort 9500ix radar detector when trying to fine out why it was laser falsing at powerup. Maybe the studio-on-wheels and my subwoofer amp can use up a lot of power. I did find out though that my Nav display was falsing the Escort! I had to move it from under the rear view mirror (using Mike's Mount) to suction cup above and to the right of the rear view.

 

well it seems that our cars require more energy to power our vehicles, since older ones dont have as many electronics, this is how i see it. Even though there are no lights running, theres those small electronics, like the alarms, security light on dash, dash clock, and misc things, so over time itll suck up all the juice. Next time just unplug, the battery, i forgot which if its Positive or negative :P

 

Its the radio's memory circuitry. You can measure the current draw with the power off. When you pull the fuse for the radio unit you will see the current draw drop. If I remember right I think it was drawing 50ma. I'm still looking for a solution.

 

I bought an '08 G35x right at the end of December and I know that the car was likely sitting for quite some time in the dealer's outdoor lot (it was snow covered when I visited it). Anyway, the dealer prepped my car in about an hour. I basically waited for it and while it was outside and started and warming up for 45 minutes while they did the overview of the features, etc., I had a problem the same night I took it home.

Not knowing, I sat in the car in my garage with the car in ACC mode, setting XM stations, programming Homelink, etc. Probably for a half hour. battery died and I had to start it with my emergency battery pack. After that, I had the Intelligent Key warning light on for the remainder of the night. Next day, car was fine.

I called dealer and was told that the battery drain is significant and 25 min on ACC in a car that has been sitting that long would likely be enough to drain it. That sounds ridiculous to me.

I carry the emergency battery pack in my trunk just in case

 

I am done trying to find out if there is a problem--I think the power draw is substantial enough that many of us are seeing this problem when leaving are cars for a few days. I ended up getting a Battery Tender Jr. I have the connector permanently affixed to the battery and use the quick connect in the windshield wiper area when I need it. I mainly drive the car on weekends and last winter found the battery dead or near dead 6 times.

 

I had no idea that the G35 batteries were suspect. This monday morning, I find for the first time that my battery is dead on the G. Sure I did not drive it on sunday, and it was cold, about 25-35 deg F in North Carolina. But I did drive about 40 miles on saturday afternoon. So after 1.5 days, the car battery died. Nothing more embarrasing than having to get your beater Volvo out for the boost, with kids waiting for a ride to school.

So my car had 18months, which seems to correlate when the battery starts with issues. I'll give my dealer a call to have the battery checked and replaced.

 

Still no problem with mine after 2 years. I leave it in below freezing weather for 2 weeks sometimes.
I will be leaving it parked for all of February and I am confident it will start when I return in March.
Oh, and mine sits outside in the snow and cold, no garage.

 

I have my car sit in a garage for more than 7 days and the battery is gone

I am almost at the point where I will buy a newer (and better) battery.

Hey Wayne, wanna swap batteries?

 

No way Andy, mine is working great. It will get the real test soon

 

I left mine for a month, all I did was disconnect the battery.

 

did you disconnect both terminals or just positive or negative terminal?

my 05 coupe sat for a week and it was dead, but it has been very cold here.

 

It was really cold here too, i just did the negative side.

 

Well it's been running 5F to 15F the last couple of weeks, so I really don't think it is necessary to pull my battery cable here for a month sitting idle. Much more than that and I would either use a battery tender or disconnect the battery.