Car alternator question

[Wolfala]

Back in August I was away on a trip and left my car at the airport for about a week. I have a 2007 Acura TL type S and have only changed batteries. Two days ago I came back from another trip from California and my car was outside for two weeks. I showed up in the brand-new battery was completely flatlined.

I remember a similar issue on my airplane where the battery was struggling to start even after a flight the night before. I pulled the alternator and bench tested it and it would always come out as testing okay. Eventually I got fed up with it and put a completely different alternator on the aircraft and the problem magically went away.

I am suspecting although I am not 100% that the same thing is going on with my car. Currently it has 113,000 miles on it. Is there any troubleshooting I should be doing on the alternator apart from the usual stuff or should I just throw another alternator on and see what happens?

[smoe]

I would check the voltage across the battery when engine running and off. If the voltage doesn't increase when the engine is running then probably a new alternator may be needed.

Also, are you sure all the interior lights are switched off?

[Wolfala]

I would check the voltage across the battery when engine running and off. If the voltage doesn't increase when the engine is running then probably a new alternator may be needed.

Also, are you sure all the interior lights are switched off?

I have the test report from AAA shows a voltage output on the alternator but things like amps which matter I could not find anywhere. Absolutely certain no lights were left on. Thinking the next step is to test for parasitic draw

[Meatwad]

Does your car have a battery guage on the dash?

[Wolfala]

My airplane does the car does not

[Buzzard7]

Almost always a current draw even with car off. ECM and radio will always have a little draw. 2 weeks may be enough to kill it. Maybe pull the cables off when you park it that long to save it. Of course your fuel trim will reset so drive the car for at least half hour once you plug it back in.

[SIK1]

On modern vehicles there is always some parasitic draw when the car is off, although it should be minimal. First thing I would do is a visual inspection of the battery, the cables, the alternator and the belt. Look to see if the sides of the battery are bulged out, and that it is full of electrolyte if you can. Make sure the cables are free of corrosion, and not just on the terminals but that the cables themselves don't have any inside the wire strands.  
What is the voltage output of the alternator, and how was it tested? When testing the alternator turn the headlights on and any other high draw items like windshield wipers, stereo, etc, and see if the voltage drops below 12.5v with the engine revved up around 1k rpm. A good alternator should maintain 13-14.5 volts even under full load if it's much below the 13v it's marginal. I've had voltage regulators go bad and they let the alternator overcharge (output more than 14.5 volts) which will quickly destroy a battery. If everything checks out it is possible you got a bad battery, and you should take it back to where you purchased it for a replacement.

[Slate]

On modern vehicles there is always some parasitic draw when the car is off, although it should be minimal. First thing I would do is a visual inspection of the battery, the cables, the alternator and the belt. Look to see if the sides of the battery are bulged out, and that it is full of electrolyte if you can. Make sure the cables are free of corrosion, and not just on the terminals but that the cables themselves don't have any inside the wire strands.  
What is the voltage output of the alternator, and how was it tested? When testing the alternator turn the headlights on and any other high draw items like windshield wipers, stereo, etc, and see if the voltage drops below 12.5v with the engine revved up around 1k rpm. A good alternator should maintain 13-14.5 volts even under full load if it's much below the 13v it's marginal. I've had voltage regulators go bad and they let the alternator overcharge (output more than 14.5 volts) which will quickly destroy a battery. If everything checks out it is possible you got a bad battery, and you should take it back to where you purchased it for a replacement.

        good info. Finding a parasitic draw can be challenging and occasionally can be the alternator. Not too common though. Do you have an aftermarket alarm system? They can cause many problems.
       A simple parasitic draw test is to disconnect the negative side of the battery and attach a test light from that cable to the negative post. (I carefully use a fluke amp meter though) The test light will be bright at first but as the modules power down it should go to dim after a few minutes. (if you disconnect the test light you have to start over) If it stays bright for a long time there may be a draw on the system. Two weeks should not kill a battery under normal circumstances. Disconnecting circuits one at a time such as the alternator wire and plug will cause the light to go dim when you find the draw 
      You must remember to have key out of ignition and door and hood latches shut as the BCM (body control module) is still active with doors and possibly hood open.

       Best to take to your local Mechanic as it can be expensive just replacing parts. 

[CAP1]

how old's the battery? if it's more than abuot 3 years old, it should be your main suspect. two weeks is kinda fast to go down, but kinda slow for there to be an electrical draw on the system, making the batttery more suspect.

[Wolfala]

how old's the battery? if it's more than abuot 3 years old, it should be your main suspect. two weeks is kinda fast to go down, but kinda slow for there to be an electrical draw on the system, making the batttery more suspect.

3 months

[CAP1]

3 months

 BRAND?  whoops...sorry bout caps locks.........anyway......if it's from autozone, advanced, pepboys, those are normally chit. napa, exide, and interstate are decent.....or as odd as it's gonna sound.....ac/delco are great batteries too.

[smoe]

BRAND?  whoops...sorry bout caps locks.........anyway......if it's from autozone, advanced, pepboys, those are normally chit. napa, exide, and interstate are decent.....or as odd as it's gonna sound.....ac/delco are great batteries too.

Thanks CAP1, my car battery needs replaced and was wondering which ones to look for.

[Wolfala]

BRAND?  whoops...sorry bout caps locks.........anyway......if it's from autozone, advanced, pepboys, those are normally chit. napa, exide, and interstate are decent.....or as odd as it's gonna sound.....ac/delco are great batteries too.

Dunno brand, AAA brought it when my last one died.

[smoe]

Dunno brand, AAA brought it when my last one died.

How old was the original one?

[Bino]

I would guess the problem is either in the alternator or the voltage regulator, with a simple short-circuit to ground a less likely possibility.