I NEED YOUR INPUT/HELP! PLEASE, Can an alternator drain a battery with car off? Options

[Random_Stranger]

Ok so I have this issue where my car battery is suddenly being drained by something. I was just wondering what first things to look at. Also what I find strange is that it didn't want to start last night (I witnessed a hit and run across the street, thought the guy was gonna stop but when he took off, I was going to jump in my car and get his license plate number, but my car didn't start). So I busted out the voltmeter and seen it was like at 9.38v. I set my alarm and went inside and later that night, I hear my alarm chirping in a way I never heard before. Then it got louder, and louder and then just went off making it's normal sound if someone attempted to break in. So I go out there and disarm it. Noticed my lights were dim and checked the reading again. It was 7.38v. I left the voltmeter connected to it and sat in the car wondering what it could be. I went back and noticed it climbed up a bit to 7.44v. I let it sit there and watched and it climbed up to 7.48v before I just disconnected it.

Is that normal for a voltmeter to do that? You think it might be my car alarm? I have an optima battery which is like 3 years old. Not sure what the life expectancy is on those or if maybe it is in fact something draining power.

This post has been edited by Random_Stranger: Jan 9, 2012 - 4:39 PM

[Neon90424]

I'd change my battery every year...maybe a lil more with an optima...

[Random_Stranger]

I'd change my battery every year...maybe a lil more with an optima...

That's not too excessive?

[Neon90424]

All my batteries keep dieing at my house lol...So I have bought about 5 batteries this year so It kinda seems like it...maybe it does take 2-3 years...

batteries last longer if you keep em inside the car...thats the reason those mercedes batteries last so long the ones under the seat...

[Random_Stranger]

All my batteries keep dieing at my house lol...So I have bought about 5 batteries this year so It kinda seems like it...maybe it does take 2-3 years...

batteries last longer if you keep em inside the car...thats the reason those mercedes batteries last so long the ones under the seat...

Yeah I know, I was told Optima batteries could only benefit from being used daily, which I do use it like that. But something is seriously draining my battery. I did some research and most people have their optima batteries for 5-8 years (and at this reported time, still going strong), even in multiple vehicles. I was hoping maybe it's just the battery and they would warranty it before it runs out, but they keep insisting on just recharging it.


I am convinced now something is draining it, as it was too low to start and the next day lost a whole 2.xx volts. I was just wondering what it could possibly be in the first obvious things to check, such as car alarm and how to check if it is in fact the car alarm that is drawing current.

[Smiles98]

Mine does the same thing, for me its to cold for the battery to maintain a good charge.

Ok the first thing to do is to run the car get the battery back to 12.2 (ish) volts turn off the car and disconnect the positive post on the battery connect a test light to the positive post on the battery and the positive cable. if your cable is grounding out than the light will turn on. also try on subwoofer power wires. (allow 2 min for light to turn off for normal systems to shutdown.)

If its not the wires, than keep the cables hooked up and turn the car to acc mode, then turn it back off and pull the key and close the door(s) the light will turn on in the test light.
wait 2 min for light to turn off if it dosn't than pull the power to the alternator (the alternator has diodes that if diffective will pull power from the battery) wait another 2 min for light to turn off. if light stays on replug alternator.
Now start pulling fuses. if the light shuts off abruptly when you pull a fuse than its in that part of the system that the power is being drawn. not the best way to find the problem but very effective.

my test light faded slowly without pulling any fuses so i came to the conclusion that im not really losing power through the system but i might be wrong.

alternator would be the first thing i would check and good luck

[pandakid]

I had an optima battery,once it died seems like it never worked the same.get it tested you should have around 5 years warrenty IIRC.unless your alarm is draining your battery

[Random_Stranger]

Ok So after disconnecting the obvious, the car alarm, I find it still draining. I noticed with car running on this "New" alternator, it bumps up to 17v which is not normal right? Ok so I after reading that sometimes a bad alternator can drain batteries, even if they do recharge the battery when the car is running, I decided to try that out.


I disconnected the alternator with the car off while I was watching the battery being drained. Wouldn't you know it? The drainage stopped after unplugging the wire that connected to the top of the alternator when installed, secured by a nut.

So here's my new question. Could it be the wire or is it the alternator itself? I noticed the wire is getting that green rust on it, but I dunno where it all goes to in order to remove the whole thing to clean it. Any suggestions? Could it be in fact the alternator? Even if it is the wire, I wouldn't know how to go about getting a new one other than just cleaning it, but that would require me to break off all that plastic coating from around the wire to get to everything. But even if that has rust, would that drain my battery from the alternator?

[Smiles98]

if you disconnected the wires to the alternator and the light went out than it has to be the alternator. the wires leaking would have kept the light on. It has to be the alternator. clean the connectors up with some sandpaper and use (dio-electic compound) when re-installing to prevent corrosion "that green stuff". you can get this at any auto zone or car parts store they sell it for installing light bulbs.

Hope this helps.

[Random_Stranger]

if you disconnected the wires to the alternator and the light went out than it has to be the alternator. the wires leaking would have kept the light on. It has to be the alternator. clean the connectors up with some sandpaper and use (dio-electic compound) when re-installing to prevent corrosion "that green stuff". you can get this at any auto zone or car parts store they sell it for installing light bulbs.

Hope this helps.

Ok thanks. I just never heard of an alternator robbing the battery of voltage before. I heard about autozone alternators doing that from other forums and what others posted when I did a search, I just wanted to verify from others, since it was something I wasn't aware of.