car battery question

NJP_MAN

NJP_MAN

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Battery keeps dying when I'm out of town for a few days. New battery so that's good. After I jump it, the alternator will charge it up just fine. Something is drawing on the battery.

Will just disconnecting the negative terminal keep the battery from draining? I can't see why not. The reason I ask is because the negative is so much easier to disco than the positive.
 
You can buy an adapter that will break the circuit,without going through the disconnect hassle.
 
Negative is the first one to disconnect anyway. Yes it should be fine. If not then the battery had an internal short. Since yours is new that shouldn't be the case
 
I have had good luck with these....just pulling each fuse and checking amperage. The car needs to be off, and make sure the hood light isn't on while you check everything. It will show you what circuit is creating the drain.
 

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You should be able to leave just about any car parked with the battery hooked up for well over a month and have it still start on it's own. You've either got something draining it beyond the normal drain to keep the radio memories and whatnot up or the battery is bad and needs to be replaced.

I'm betting you just need a new battery. If it's more than 3 years old I'd just replace it. Car batteries seem to fail in 3-6 years although I have seen some go far longer.
 
A shorted diode in the alternator will do that. It will let the alternator muscle through with a mediocre charge while running, but then provide a sneak discharge path while the engine is off. Another sign of a shorted diode is an unusual whine from the alternator while the engine is running
 
I thought it was the battery but the one that I replaced was 2 months old so I thought it was bad. The brand new battery yielded the same result. I dont really care too much to solve the draining problem at the moment but eventually I will find some time to wring out the issue.

Edit: we disconnect the plane batteries when we park them so I don't much mind to disco the car batt when I park it for 3+days.
 
Well if pulling the negative cable works, then there you go..
 
Grab an ohm meter and start pulling fuses. I had a problem with my battery dying and the alarm randomly going off. Turned out the hood stopper was holding the hood from fully closing and the light was running, than the wind would rattle the hood and set off the alarm. Drove me nuts till I finally started to go through the fuses took 10seconds to fix once I saw what was wrong.
 
NJP_MAN said:
Battery keeps dying when I'm out of town for a few days. New battery so that's good. After I jump it, the alternator will charge it up just fine. Something is drawing on the battery.

Will just disconnecting the negative terminal keep the battery from draining? I can't see why not. The reason I ask is because the negative is so much easier to disco than the positive.
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In the dark, take a camera with a timer (most phones now work) and put it under the hood, and in the trunk, to make sure the light is going out.
 
Each time you disconnect a battery on a modern car with EFI, the ECU for the fuel and ignition go into a default mode. Running the car after that sets calibration values in the ECU(s) which are defined by the compression ratio, spark quality, dirt in the air cleaner, age of O2 sensors etc. Disconnecting the battery should be a short term fix for this. You should find the current draw soon, and leave the battery connected.

You will notice slightly worse fuel economy, and maybe performance if you keep doing this. It may also affect your O2 sensor and more important the cat(s) depending on the car. It's never getting through it's complete drive cycle which is anywhere from 22 miles up to ~85 miles.

Hints - Most cars have a Ign Off circuit which services acc lights, and the remote door locks and security. Look in your fuse list and see if you see something called IOD (Chrysler) or similar for other makes. You can also look for what the fuse services the ones for acc lights and remote entry. Take just that fuse out and see how it goes. Later, you can get the little fuse tester and find the circuit correctly. Now, look in the glove box see if the little post to shut off the light is working. Or go in there in dark of night, and see if there is light around the glove box. This fixes about 30% of batt drain issues.
 
Thanks cowboy. I will go look now and report my findings.
 
No light at all under the hood. The glove box checked out ok and the sun visor mirrors were good too. Its a 2002 maxima if that makes a difference. Its a head scratcher for sure.
 
NJP_MAN said:
No light at all under the hood. The glove box checked out ok and the sun visor mirrors were good too. Its a 2002 maxima if that makes a difference. Its a head scratcher for sure.
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Diodes in the alternator. When they go, when you shut off the engine, the alternator goes into motor mode and will drain the battery.
 
Next culprit is radio or antenna amp. Usually it's accessory related. Might have to go the fuse route. Another way to try is to begin pulling fuses with the engine running and see how many you can remove and still have the engine run. Once you get to a minimal set of fuses, put a voltmeter on the battery, and put the fuses in one at a time. Wait a few seconds and watch the voltage. When the drain fuse is inserted, the voltmeter will start counting down.
 
Henning said:
Diodes in the alternator. When they go, when you shut off the engine, the alternator goes into motor mode and will drain the battery.
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So is this just replace the alternator kind of problem? I have only ever had the alternators eat themselves up and fail to charge. So the diode thing is new to me.

And can we get some more hostility in this thread? This has been way too helpful and I'm afraid that I'm not really on POA forums.
 
NJP_MAN said:
So is this just replace the alternator kind of problem? I have only ever had the alternators eat themselves up and fail to charge. So the diode thing is new to me.

And can we get some more hostility in this thread? This has been way too helpful and I'm afraid that I'm not really on POA forums.
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Yep you ****ing moron, but I guess an idiot like you wouldn't bother taking it down Auto Electric shop and have it tested first and just have them change the diodes for $35.

Better?:lol:
 
Henning said:
Yep you ****ing moron, but I guess an idiot like you wouldn't bother taking it down Auto Electric shop and have it tested first and just have them change the diodes for $35.

Better?:lol:
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That's more like it you A hole! Thanks for nothing. I'm going to take it down to an auto electric shop and have them change the Diodes for $35 instead.
 
Henning said:
Yep you ****ing moron, but I guess an idiot like you wouldn't bother taking it down Auto Electric shop and have it tested first and just have them change the diodes for $35.

Better?:lol:
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Who is the moron? change the bearings and brushes while it is open. After all, that alternator has been in service for over 10 years. Sheesh, even an apprentice seaman knows that.


(just doing my part)
 
FWIW, I had a drain problem in a car of mine. Turned out to be the electric trailer brake. Didn't notice it with a new battery and daily usage. Killed 2 batteries before I could figure it out when I stopped driving it every day.
 
I had the same problem with a car I had once. Turns out the ground cable was rusted through.
 
Remove the positive battery cable. Take one lead from your multi-meter and touch the battery cable. Now take the other lead and touch the battery positive terminal. This will show what voltage is being drained. Start pulling fuses until you find your drain. All modern auto's have some drain but its not a lot. I have a book somewhere that shows what each model of car should pull as to voltage drain.
 
1600vw said:
Remove the positive battery cable. Take one lead from your multi-meter and touch the battery cable. Now take the other lead and touch the battery positive terminal. This will show what voltage is being drained. Start pulling fuses until you find your drain. All modern auto's have some drain but its not a lot. I have a book somewhere that shows what each model of car should pull as to voltage drain.
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That's a current drain measurement with the meter in series with the entire load. Voltage measurements are parallel, with the terminals connected to the battery, and the voltmeter being used as a monitor.

Your method will work, but the meter must be set to Amps not Volts, and I would strongly suggest you have a 10 amp range to start, then change to 2 amp range, and then lower.
 
docmirror said:
T
Your method will work, but the meter must be set to Amps not Volts, and I would strongly suggest you have a 10 amp range to start, then change to 2 amp range, and then lower.
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You also must put the ammeter in series with the circuit to measure current (or read it through a shunt). There are clamp on DC ammeters, but you're spending real money to get an accurate one and even then they're a bit finicky. At the very low currents we're concerned with here, I'm not sure you'll get a reading.
 
flyingron said:
You also must put the ammeter in series with the circuit to measure current (or read it through a shunt). There are clamp on DC ammeters, but you're spending real money to get an accurate one and even then they're a bit finicky. At the very low currents we're concerned with here, I'm not sure you'll get a reading.
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Please read post 24, which I quoted and describes a series connection with the meter. So, I felt it wasn't necessary to describe again.
 
docmirror said:
Please read post 24, which I quoted and describes a series connection with the meter. So, I felt it wasn't necessary to describe again.
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Oops, never mind I didn't realize the error you were correcting.
 
Good point raised about the cables. Make sure all the connections are clean and tight, very tight. This includes all ends of cables. Start simple and work your way to more complex. The battery won't charge properly with corroded connections.
 
Find you parasite load and deal with it. In my trucks it's been the addition of aftermarket bluetooth-capable stereos. My inactive battery life was perfect until I added the stereos and now my batteries will die in a month if the vehicle isn't driven. I manage it by pulling the stereo fuse if I'm leaving town. I could easily add a power switch upstream of the stereo itself but I haven't gotten around to it.
 
docmirror said:
Please read post 24, which I quoted and describes a series connection with the meter. So, I felt it wasn't necessary to describe again.
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Like I didn't think I had to tell a guy to turn off the water at the meter before changing faucet washer. His wife yelled at me for that. :D
 
Norman said:
Like I didn't think I had to tell a guy to turn off the water at the meter before changing faucet washer. His wife yelled at me for that. :D
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Did ya yell back that maybe she shouldn't have married a plumbing moron if she was going to complain about his work?
 
NJP_MAN said:
Battery keeps dying when I'm out of town for a few days. New battery so that's good. After I jump it, the alternator will charge it up just fine. Something is drawing on the battery.

Will just disconnecting the negative terminal keep the battery from draining? I can't see why not. The reason I ask is because the negative is so much easier to disco than the positive.
Click to expand...

Some cars have drains. My BMW would kill new, fully charged battery in a few weeks of no use. I used to keep it on the battery tender in the winter when the car was rarely used.

I would be very careful disconnecting battery completely. Some cars(probably just about all of them now) really do not like it as the ECU gets reset and it takes some time for the car to learn how to work correctly again. At least 2 cars I've own do that. 97 F150 would literally die @ idle for the first 30-50 miles after battery change and my wife's Outback runs like crap for the first couple of days after battery disconnect. All until they relearn mapping and shift points.

You really should just start pulling fuses(or just test them) and try to isolate the issue.
 
A more direct annoyance - disconnecting the battery will dump your radio and activate the anti-theft lock if you have one. Know where the code is if you want to listen to it. When I last changed a battery, I didn't care much that I got worse mileage for a little while, but not being able to have a clock or some music was a real downer.

Otherwise, what everyone else said.
 
bflynn said:
A more direct annoyance - disconnecting the battery will dump your radio and activate the anti-theft lock if you have one. Know where the code is if you want to listen to it. When I last changed a battery, I didn't care much that I got worse mileage for a little while, but not being able to have a clock or some music was a real downer.

Otherwise, what everyone else said.
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That too.. :)

Of course it is always entertaining when the engine dies as you come off the gas into a turn. That(brake and steering) put just a little too much load on too-low idling truck. And you simultaneously lose power steering and partial brakes effectiveness while attempting to make a sharp turn at speed with a 2.5 ton truck. That was my F150 behavior for a few dozen miles after a battery disconnect..
 
If you do a draw test after you connect your meter wait about 20 min before you test... It takes about that long for all the modules to go back to sleep.
 
docmirror said:
That's a current drain measurement with the meter in series with the entire load. Voltage measurements are parallel, with the terminals connected to the battery, and the voltmeter being used as a monitor.

Your method will work, but the meter must be set to Amps not Volts, and I would strongly suggest you have a 10 amp range to start, then change to 2 amp range, and then lower.
Click to expand...

But that's my favorite way to fry a multimeter... that or accidentally leave it in ammeter mode on the unfused side and think I'm measuring voltage at the terminals lol
 
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