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I think this has been talked about a lot but I'm currently in this boat and am looking for guidance. Car has had an issue where the battery dies after 30+ miles on the road. i changed the battery out along with the alternator and it did it to me again this past weekend. I just recently found the dash option for battery voltage and under normal driving it stays at 14.5 volts I did see that under acceleration it dropped to around 12 volts and took a few minutes to get back to charge. any suggestions would be appreciated.
 

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Not nearly enough experience, been lucky with that (so far), so good luck.
 

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Does it die sitting overnight?

If you have a clamp-on style amp meter, see what the current draw is with the engine off. It should be reading in the milli-amp range which is just enough to keep the memory on various components and things like your clock running. If it's drawing an close to an amp or more, keep the tester on and start pulling one fuse at a time until the draw disappears. The cover of the fuse box has the legend printed on the interior of it for quick reference.
It's a good starting point, let us know how it goes.
 

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I don't understand "battery dies after 30+ miles on the road". The car is running, you drive it 30 miles, it's still running. How do you know the battery has died? Define "dies", what exactly are the conditions of failure?
 

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Have you tested the output of the alternator directly? After starting the car, will it stay running with the battery disconnected (i would check the alternator output before douing this).
 

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I don't understand "battery dies after 30+ miles on the road". The car is running, you drive it 30 miles, it's still running. How do you know the battery has died? Define "dies", what exactly are the conditions of failure?
That scenario almost always means the alternator is not keeping up with the electrical demands of the car. The car makes it about 30 miles off the energy supplied by the battery then dies.
 

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Well that's what you'd get if the battery wasn't charging. The voltage while the engine is running is mostly unrelated to the battery. There's a voltage regulator working to make sure of that. Start the engine and disconnect the battery and the voltage shouldn't change much whether the battery was charging correctly or not (note: don't actually do this. I think the GM charging system will be damaged if the engine runs without the battery connected). The problem is definitely in the charging circuit. 14.5V is what you'd expect to see from the Alternator when there was minimal load. The battery not taking a charge would certainly qualify in that regard.

What you need is a clamp-on Ammeter, which you can then clamp over the positive lead of the battery. And then you can measure both the cranking amps and the charging amps and maybe zero in on the issue.

Clamp-ons use magnetic induction to measure the current flow, so there's no direct electrical connection. Measurements are not affected by insulation. A typical Clamp-on meter will be good measuring as much as 600 to 1000A.
 

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I have an idea for you... I had this exact issue and it went away on "accident".

It happened one day after I disconnected the battery for something then connected it again.... I put the left terminal (facing the battery, the left one, +?) on parallel to the battery. Then for months I had charging/discharging problems. I then "accidentally" put the terminal perpendicular to the battery and voila, never again had an issue. Post a pic of you battery clamps as the currently sit and lets see if my theory works.

My car could go over a week with no issue, then boom, dead battery in a matter of hours. I'm assuming the clamp must've made contact with something behind the carpeting on bump or something, because the issue came and went. On a whim, I moved the terminal placement and I never again had the issue.
 
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