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Discussion Starter · #1 ·
Left town on Saturday and wife calls me on Sunday saying she tried to start the SRT8 but the battery was dead. I got back Sunday afternoon and there was just enough juice in the battery to make the instrument panel lights flicker - not even a dome light. Put the charger on it for 10 hours overnight and in the morning the starter was barely able to crank the engine over, but it did start. Since it was started I ran it over to the dealer. They measured an 800 milliamp draw on the battery with the ignition off, but it went away after they opened and closed all the doors. The service manager speculates that it might have been a door switch stuck - but not enough to engage the dome light. Sounds quite speculative....

Anyway, their check on the battery indicated no problem there, I drove off...

Now I wait and see if it happens again.
 

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jmk said:
Left town on Saturday and wife calls me on Sunday saying she tried to start the SRT8 but the battery was dead. I got back Sunday afternoon and there was just enough juice in the battery to make the instrument panel lights flicker - not even a dome light. Put the charger on it for 10 hours overnight and in the morning the starter was barely able to crank the engine over, but it did start. Since it was started I ran it over to the dealer. They measured an 800 milliamp draw on the battery with the ignition off, but it went away after they opened and closed all the doors. The service manager speculates that it might have been a door switch stuck - but not enough to engage the dome light. Sounds quite speculative....

Anyway, their check on the battery indicated no problem there, I drove off...

Now I wait and see if it happens again.
I like that word "speculative". About covers anything they can't put their finger on. And the part about not engaging the dome light! What is that???

800 milliamps might be about what (1) interior bulb would draw, but the door switches, at least in my car, turn on like a half dozen bulbs!

I am going to go with the idea that I proposed with someone else's dead battery mystery: the trunk lid wasn't fully closed enough to flick the switch and turn off the trunk light. My theory has yet to be proved or disproved, but it is (in my mind anyway) definitely a strong possibility. Either the switch (which is mounted in the latch mechanism in the trunk lid) is touchy, or the trunk lid wasn't fully closed. While exploring for the problem you/they may have inadvertently solved the problem by closing the trunk. Or maybe when they measured the 800 ma. they had the trunk open without removing the bulb or snapping the trunk latch to its closed position. NAH!
If you can, leave one of the back seat backrests in the down position so that any light in the trunk compartment can be easily seen.
 

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DESIREE said:
I like that word "speculative". About covers anything they can't put their finger on. And the part about not engaging the dome light! What is that???

800 milliamps might be about what (1) interior bulb would draw, but the door switches, at least in my car, turn on like a half dozen bulbs!

I am going to go with the idea that I proposed with someone else's dead battery mystery: the trunk lid wasn't fully closed enough to flick the switch and turn off the trunk light. My theory has yet to be proved or disproved, but it is (in my mind anyway) definitely a strong possibility. Either the switch (which is mounted in the latch mechanism in the trunk lid) is touchy, or the trunk lid wasn't fully closed. While exploring for the problem you/they may have inadvertently solved the problem by closing the trunk. Or maybe when they measured the 800 ma. they had the trunk open without removing the bulb or snapping the trunk latch to its closed position. NAH!
If you can, leave one of the back seat backrests in the down position so that any light in the trunk compartment can be easily seen.
What he said.
 

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I had this happen 2 till i reilized it was the trunk. I put a switch in the light that way if the truck latch switch doesnt catch the light wont be on in the first place.
 

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How could you not notice the trunk being open? If it doesn't latch it would be obvious it's not shut all the way.
 

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It's not that Obvoius and were also talking about the switch in the lacth not just the lid open.
 

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Discussion Starter · #8 ·
I took all your advice and left the rear seats down and checked for a light after the car was parked. No light, no evidence of any peculiar electrical activity. Got to work and then decided to go out and check the car again. Went into the EVIC diagnostic mode - battery voltage read 10.8. Not good. Car barely cranked over - but did start. Drove directly to the dealer again. He puts on his battery diagnotic tester - which diagnosed to replace the battery. Half hour later, back on the road again. Faulty battery after 8 months and 7000 miles. Hopefully this is the end of it and not some other electrical gremlin.

I have had the worst luck with factory batteries. If I get a year out of them I count myself lucky.
 

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10.8 volts is within the range of a "fully charged battery" with one dead cell.

It's also in the range of a battery with almost no charge. You might want to make sure to check the voltage (at the battery) when the engine is running just to make sure the new battery is charging properly. 13.6-14.4 volts.


State of Charge 12 Volt battery Volts per Cell
100% 12.7 2.12
90% 12.5 2.08
80% 12.42 2.07
70% 12.32 2.05
60% 12.20 2.03
50% 12.06 2.01
40% 11.9 1.98
30% 11.75 1.96
20% 11.58 1.93
10% 11.31 1.89
0 10.5 1.75
 

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jmk, I'm like you; the factory battery never seems to last very long. Usually less than 2 years. My one exception was my '96 Ford Windstar, that one lasted 9 years, and almost 2 months. When I had to replace the battery and the alternator.
 

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Discussion Starter · #11 ·
Thats a handy little chart there for battery charge condition. The EVIC display reads out about 14v when the car is running. I will keep an eye on the battery voltage after it sits for a while. It is easier to read the battery voltage by dropping into the EVIC diagnostic display when the car is not running than by popping the hood or trunk and hooking up my multimeter.

Who knows, there may really be a small intermittent current drain on the system and the battery failing may be the effect rather than the cause.
 

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Some new batteries are defective. I once had a 3-month old replacement take a dump. The battery in my 97' Mustang Cobra is original. It will be 9 years old in February. It has slowed down a bit recently which I attributed to a corroded positive terminal. The Cobra goes away for the Winter in a couple of weeks. The battery may not survive to next April.
 
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