[BobSaabit]

My battery has died a couple times recently. Once after just sitting inactive for a month. Would not start. Then again after using the radio (only) for about 45 minutes a few days ago. Hardly the sort of draw that should kill a battery. I used to listen to the radio, with an old battery, in cold weather, through two or three hour-long cycles when working on the car, with no ill effects.

The battery is only about a year old. I believe it's a Johnson Controls battery (relabeled, of course) and those are usually good for five years... perhaps three in this hot climate. I'm not in a cold climate so it's not a cold-weather thing. Definitely seems premature.

Alternator shows 13.6 volts at the battery when idling / charging. It's a Bosch, replaced also within the last year or so (was definitely having issues). Battery was replaced after that. After driving just a short distance (jumped car to start), battery showed 12.6v. so charging seems fine. I did put it on the charger for a few hours and charged it back up to full charge.

The failure a couple days ago (radio on 45 mins) was after a ten minute drive. I figure that if it was mostly discharged before starting that perhaps it didn't have time to re-charge on the short drive. \

TL; DR: -i.e. the real question:

I know it could be a bad battery, but to the point of this long post, I think I should measure car-off draw before asking for replacement under warranty.

I know some circuits time-out after an hour. I'm thinking that I need to hook up the ammeter between the battery and the main positive lead, let the car sit an hour, then look at the draw. I figure if I do anything like open a door that I might trigger a reset on the hour wait.

Thoughts on that? How much draw should I see initially and then after an hour?

Also, do I need to tie down the hood alarm switch? My alarm is "not installed" in Tech II, but I suspect it still draws current in that configuration.

Thx,

 

[Germaniac]

Why not being a faulty battery? Maybe you can borrow one in known good condition and try to reproduce that "effect".

(Your trouble reminded me of our workshop having to deal with a good number of batteries being dead after around a year which were installed in new cars, and the car manufacturer started a recall on them.)

 

[jvanabra]

If you want to tackle this at the battery and not at the fuse, I would get something like this:

Advance Auto Parts - Down for Maintenance

Install it temporarily... it will give you a place to put the ammeter without disconnecting/reconnecting and possibly waking something up.

 

[BobSaabit]

If you want to tackle this at the battery and not at the fuse, I would get something like this:

Advance Auto Parts - Down for Maintenance

Install it temporarily... it will give you a place to put the ammeter without disconnecting/reconnecting and possibly waking something up.

Probably more than I'm willing to spend for a test, LOL.

What about setting up the draw, then just waiting? Is there a flaw in that plan?

 

[jvanabra]

I'm not sure what you mean by "setting up the draw." If I understand what you're trying to do, you'd need to have the ammeter connected from the time the car is shut down until ... 30 or 40 minutes later after everything has gone to sleep. To do that you would need to have an ammeter capable of handling everything from many dozens of amps (car is running) to several amps (car is off) to fractions of amps (everything has gone to sleep). You would need a pretty expensive ammeter to do that. Maybe you've got one?

 

[aerojon]

charging voltage should be minimum 14.2-4v+

 

[EdT]

Parts stores and/or mechanics have battery load testers. How much I would trust one depends on how pimply the kid doing the test is. But that could be the way to go. I know that NAPA will test its own batteries to see if warranty replacement is warranted.

 

[Saaberachi]

Bob do a quick alternator diode test just to rule it out

 

[mio]

Parts stores and/or mechanics have battery load testers. How much I would trust one depends on how pimply the kid doing the test is. But that could be the way to go. I know that NAPA will test its own batteries to see if warranty replacement is warranted.

I bought a cheap ($25) battery tester a few years back and have found it to be very useful.

 

[BobSaabit]

Bob do a quick alternator diode test just to rule it out

Tell me more.

 

[BobSaabit]

I'm not sure what you mean by "setting up the draw." If I understand what you're trying to do, you'd need to have the ammeter connected from the time the car is shut down until ... 30 or 40 minutes later after everything has gone to sleep. To do that you would need to have an ammeter capable of handling everything from many dozens of amps (car is running) to several amps (car is off) to fractions of amps (everything has gone to sleep). You would need a pretty expensive ammeter to do that. Maybe you've got one?

Is it really drawing that much? I'm thinking that once you shut off the car, and without the lights off, the only things up are the ECU, maybe a little for the twice and dice (assuming the fan doesn't kick up). That should be under an amp, correct?

 

[BobSaabit]

Parts stores and/or mechanics have battery load testers. How much I would trust one depends on how pimply the kid doing the test is. But that could be the way to go. I know that NAPA will test its own batteries to see if warranty replacement is warranted.

It's 50/50 on whether the store replacing it will test it or not or just exchange it... or whether they will be qualified as you noted. I'd like to eliminate the draw being the issue ahead of time though. No sense replacing it if the issue is a high draw.

charging voltage should be minimum 14.2-4v+

Thanks. I'll check in with Bosch and see what they say. I'm still under warranty so perhaps it will need replacement.

 

[Saaberachi]

Tell me more.

Sorry about the poor writing. That alternator should be putting out higher voltage as someone mentioned earlier. When my diodes failed the alt still put out 14v but was causing a 2amp backdraw with ignition shut off. It would pull my perfectly good battery down to 10 amps overnight. Totally dead, Tested in between negative cable & negative battery post after 2 minutes with key removed from ignition, doors closed

 

[jvanabra]

Is it really drawing that much? I'm thinking that once you shut off the car, and without the lights off, the only things up are the ECU, maybe a little for the twice and dice (assuming the fan doesn't kick up). That should be under an amp, correct?

Hard to say... You could always hook up the ammeter and hope you don't blow it, I suppose.

 

[Saaberachi]

After you shut the car off, close the door, leave alarm unarmed. Wait a couple minutes & check the backdraw on the battery ground. I think mine goes down to 25 milliamps or so on my 03 vert se

 

[ewgoforth]

It's 50/50 on whether the store replacing it will test it or not or just exchange it... or whether they will be qualified as you noted. I'd like to eliminate the draw being the issue ahead of time though. No sense replacing it if the issue is a high draw.



Thanks. I'll check in with Bosch and see what they say. I'm still under warranty so perhaps it will need replacement.

I like to get my batteries tested at a competitor of the Auto Parts store I bought them from. The shop I bought them from has an incentive to say they are good, assuming it's still under warranty.

 

[BobSaabit]

I like to get my batteries tested at a competitor of the Auto Parts store I bought them from. The shop I bought them from has an incentive to say they are good, assuming it's still under warranty.

Good point... although the store testing has an incentive to say it's bad. LOL.

 

[BobSaabit]

After you shut the car off, close the door, leave alarm unarmed. Wait a couple minutes & check the backdraw on the battery ground. I think mine goes down to 25 milliamps or so on my 03 vert se

What do you mean by "backdraw"? How / where are you measuring?

 

[Saaberachi]

Pull neg cable off battery & put one lead on battery post & the other on neg teminal on cable end. After 2 min with everything off on the car. If your getting a significant reading then the system is back drawing on the battery. ( more than normal) like i said earlier i had a bad diode in my bosch 140A alternator that was pulling 2.1A all night. I'd come out to start it in the morning & my battery was down to 10 volts. I didnt know what was causing the problem untill i did the diode test on the alternator. Put in my spare 130A unit & all was good again
Idk if thats your problem or not but its quick & easy to test it

 

[wdssaab]

Take a look at this thread of a 2007 9-5 on drawdown. He is checking the drawdown amps and isolating the various Maxifuses. I spoke with the owner last night and the car seems to be doing fine. I believe it was his driving habits, putting the standard shift in neutral and coasting downhill. He has changed his driving habits and the 9-5 seems to be doing ok.