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dieing battery, 1970 cadillac

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Member - Posts: 3
Member spacespace
Joined: September 26, 2006
Location: United States
Posted: March 14, 2007 at 10:42 AM / IP Logged  
Alright, I have had this problem with my car for some time now, and I thought this would be a good place to seek help. First off the car is a 1970 Cadillac hearse. Which from what I can tell is based off a fleetwood. This started happening about 2 years ago. So I replaced the battery and it worked fine again, for awhile. Then about 6 months ago it started happening again.
The problem is that if it sits for a period of time, like a week or so, it won't start up. You turn the key and it clicks, idiot lights dim, and it doesn't do much anything else. Then when you go to jump it, it won't jump right away. You have to let it sit there for awhile connected up to the other car until it will start. It takes a good 10 minutes before it will even think about trying to start.
I'm guessing the battery is bad again, but thats another question, batterys should last longer then that. I mean the first battery I put in it lasted for atleast 2 years. Up until it started dieing I could leave the headlights on for 9 hours with the car off and it would start no problem. Now this second battery is dieng after just over a year. So is something killing my battery? Would that mean theres a short somewhere?
I took some readings and when I first got to my grandpas garage and turned the car off the battery read at 12.21volts. I started the car up and it read at 14volts. The parasitic load is at .45mA. If I unplug my stereo that goes down to 0. Then after doing all this I check the voltage again, and it read at 12.12. So in about an hour it went down .09volts and most of the time it wasn't even pluged in.
So basically if I drive the car every day, it works just fine never have a problem with it. If I don't drive it for about a week or so, it's dead. I'm trying to figure this out, in the past I had a lot of electrical problems. I have replaced the regulator, alternator, and starter all withen the past 2 or 3 years. Starter was the ealiest, that may be closer to 4 years ago. Anyways though, any ideas or suggestions would be great, let me know if you need to know anything else. Thannks in advance.
Member - Posts: 3
Member spacespace
Joined: September 26, 2006
Location: United States
Posted: March 14, 2007 at 12:18 PM / IP Logged  
Alright, so I tested the battery again, and its now at 12.07 volts. So it has droped some more, and it has been un-plugged from the car. It did this in about 2 hours. So it would seem the battery is whats wrong. My question is then what would cause the batter to wear out like this? It shouldn't be bad already. And why would it take so long until it is able to be jumped?
Mad Scientists 
Silver - Posts: 380
Silver spacespace
Joined: February 07, 2004
Location: United States
Posted: March 14, 2007 at 7:51 PM / IP Logged  

It could be a bad battery, but it could also be a charging system or connections problem. The battery should be reading more than 12.2 volts when you shut the motor off.. I'd charge the battery on a charger and see what the voltage does.. I'd expect 12.6v or so about a day after the battery was taken off the charger.

Did you measure AC voltage at the battery when the engine was running?


Member - Posts: 3
Member spacespace
Joined: September 26, 2006
Location: United States
Posted: March 14, 2007 at 9:40 PM / IP Logged  

Voltage while the engine is running is about 14 volts. It fluctuates a bit, but right arount 14v.

I was thinking it was a bad battery, but this battery is only a year  or 2 old. The old battery did the exact same thing. So I am kind of starting to wonder if something could be frying  the battery. I will try putting it on a charger, getting it fully charged and see how it sits.

Silver - Posts: 695
Silver spacespace
Joined: November 20, 2004
Location: United States
Posted: March 16, 2007 at 12:01 PM / IP Logged  
Hmm... I worked on many conversion vans that did this same thing.. to many cheap gizmoz in them. especially when they sat for a week or 2. we used to install battery buddies on them. at a given voltage, this would cut any load being drawn on the battery. (installed in line with the (+) cable. They worked really nice. The other thing is to install a battery cut off switch [wether remote or pop the hood and flip the switch. In your case that is what I would do. It sounds like you have a bad battery, and if the car isn't driven a lot, It's just going to happen sometimes. My 48 GMC does it as does my 56 chev both have batt cut off switches in them and I have no problem. when ya get a new battery, just go to wal mart [ick] and by a everstart with a lifetime warrenty. If the problem persists then once a year return the batt and get a new one... I do that with my mud truck battery every year...
Tire Proz Stillwater Mn
High End Restyling and Comlete Repair

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