Draining Battery...

[Coil99]

I have what I think is a simple (and dumb) question. How long should it take for a battery to drain (and be completely dead) when the SHO is just sitting?

My battery died on Sun, July 25th and I bought a new one that same day. Due to rain, I was not able to connect the new battery until the following weekend, which was Sat, July 31st.

I connected the new battery and then drove to AutoZone, which is about 10 minutes - if that - from my house. They put the machine to my SHO to confirm my alternator was shot. I then drove the car straight home and parked it in the driveway. I did not use the a/c, lights, etc. - I did crack the windows a little though. In total, I used the battery for about 20 minutes.

I went out this morning to get something out of the car and the battery is completely dead. Does that sound right? Thanks for any thoughts.

 

[Ishodu]

Yeah that sounds about right you were running your car just off the battery. Your going to want to get it charged up to 12.6 Volts or close to that. Before you start it with your new alt also.

 

[Coil99]

Your going to want to get it charged up to 12.6 Volts or close to that. Before you start it with your new alt also.

Because it will damage the new alternator?

 

[Coil99]

Thanks for the info!

Yeah that sounds about right you were running your car just off the battery.

I know I could be wrong, but it just seemed like the battery drained awfully fast. It makes me think there may be something else going on.

 

[Ishodu]

Because it will damage the new alternator?

Yes it is not good for it.

 

[Ishodu]

I know I could be wrong, but it just seemed like the battery drained awfully fast. It makes me think there may be something else going on.

You can have a major amount of power draw on. How long does it take with your lights left on to drain your battery? Well just think you have your ignition system running, your fuel pump, maybe your fan the list goes on. You are drawing a lot of power if your just running off the battery.

 

[Rob94]

I drove half an hour, at night, with heater on full blast with a crapped out alternator. The next day, car fired right up, brought me to parts store to get alternator, and back home. With that said, if your new battery sat on the parts store shelf for a while before being sold to you, I suppose it could have been "less than fresh". But, most battery manufacturers design their batteries so that if you lose charging capability, you are still capable of driving short distances (25 miles or so) to the nearest repair facility. 20 minute drive and dead battery....I'd throw a tester on it and see if something is drawing current while the car sits. Like you, I suspect something is amiss.

 

[rangerj]

Put a full charge on the battery before doing an "amp draw test". Remove the bulb from the under hood light, otherwise it will draw current. Let the car sit without opening any doors or turning anything on for about 5 minutes so any "time delay" devices have time to "switch off".

Now with an amp meter check the battery for any amps being drawn. the computer draws about 15 miliamps (or less - as little as 5ma). If you are getting an amp draw start looking for the problem, such as a glove box light stuck "on", or the trunk light, dome light or something else you may have wired "hot".

Before you start the tests make sure you have good connections to the battery and the engine, including the main ground connection to the engine block.

If the draw is not coming from something obvious, such as the items mentioned above, then you start pulling fuses, one at a time, so you can isolate the circuit that has the "draw" on it.

Remember, each time you open the door it may activate a time delay device that will draw current. You have to wait for the device to turn off before doing any testing. Once you find the circuit that is drawing current you can test the items on that circuit for a short to ground, failed relay, etc.
rangerj

 

[Coil99]

Thanks again for all the information.