dieing battery, 1970 cadillac

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.

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?

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...

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