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I've recently started having a bit of trouble with my car. I typically drive my car to and from work each day. A couple weeks ago I went on vacation and when I returned, my car battery was as dead as could be. The battery was already a couple years old, so I went to the local auto parts shop, purchased and installed a new battery.

This morning, after it had sat through the weekend, it wouldn't start and was completely dead. I drove the car at lunch, and it started without any trouble. Furthermore, other than the incident a couple weeks ago and this morning, I haven't had any form of trouble starting my car. It's always started quickly, without any trouble.

I checked how many amps the care was pulling while it was off and it was .78 amps. Could this slowly kill my battery after a few days or is that a normal power draw for a car that isn't running?

FYI, My car is a 95 Buick LeSabre. Also, I'm not 100% sure that the lights weren't on a couple weeks ago, however, I am sure that my lights were not left on over the weekend, nor were the internal lamp lights. If something is drawing power, it's something that isn't immediately noticeable.

While a typical car is off, how many amps does it pull from the battery?

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Do you have a security system that could be triggering something, and waking the car up? – FossilizedCarlos Jun 19 '12 at 2:57
No, there is nothing like that. I'm thinking it could be a bad relay that's stuck in an open state. However, before I start pulling fuses and testing the amps I thought I'd verify whether .8 amps was high or not. – RLH Jun 19 '12 at 12:09
what did you use to measure current draw when the ignition was off? 0.78A seems incredibly high. – Rory Alsop Jun 25 '12 at 12:36
Rory Alsop: I used an Amp/Voltage meter. I work in engineering and I was assisted by an electrical engineer. Or should I really say... I was assisting an electrical engineer who was helping me solve this problem. – RLH Jun 25 '12 at 12:43

1 Answer

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Not sure what it "should" be pulling, but anywhere near a whole amp is way too much and will drain the battery in no time. Are you sure you tested right? Often the pull when you first connect the battery can be a lot higher than the steady pull since you might be charging some capacitors, etc. If it stays that high you definitely have a problem, possibly a partial short.

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R..: I disconnected the negative terminal and measured the draw with a meter from the line to the battery. A couple days later, I started pulling fuses and measure the current from the fuse box. I found a line (for the power mirrors/interior lights at my feet) that was pulling about .63 amps. Since I don't need floor lights and my mirrors rarely need to move, I just pulled the fuse until I can take the car into the shop. So far this has helped. – RLH Jun 25 '12 at 12:45

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