Bizarre battery behavior

[jwakil]

I've been having some strange battery issues lately. My battery has died after sitting for short periods (1 day to 1 week at different times) and so I've been suspecting maybe there is a draw somewhere. I've taken the battery to get checked twice and they say it is good after chargeup. My previous experience with other batteries when there is a draw it would usually go down to ~0V and kill the battery, especially after sitting for a week or longer. Here the battery usually only goes to 11V. This last time the battery voltage was down to 9V. I had to jump start the car and noticed my alternator wasn't charging at all, and none of my gauges worked (even though the car ran). So I figured maybe my alternator is crapped out and it's not charging the battery. However, after I trickled charged the battery and turned the car on, the alternator started charging as well. So is there any way that the battery being bad or too low would stop the alternator from charging as well? Now with the battery charged up everything is working normal, however, I fear same thing will happen again.

[Ian Comerford]

I guess the first thing is to test your charging system to understand whether the alternator is working. I think I recall running the engine at around 3k revs and checking to see if the battery is getting at least 13.6v.
I had some battery issues this year and bought one of these to attach to the battery Andre lately monitor it via an app. It has been really useful
https://www.amazon.co.uk/Battery-Monitor-Campervans-Compatible-bluetooth/dp/B08VHMJYXY/ref=sr_1_5?keywords=12v+battery+monitor&qid=1649862011&sr=8-5

[jwakil]

Originally Posted by Ian Comerford

I guess the first thing is to test your charging system to understand whether the alternator is working. I think I recall running the engine at around 3k revs and checking to see if the battery is getting at least 13.6v.
I had some battery issues this year and bought one of these to attach to the battery Andre lately monitor it via an app. It has been really useful
https://www.amazon.co.uk/Battery-Monitor-Campervans-Compatible-bluetooth/dp/B08VHMJYXY/ref=sr_1_5?keywords=12v+battery+monitor&qid=1649862011&sr=8-5

Of course when I say my alternator started working fine after battery recharge I base it on the voltage being near 14V when running.

[proporsche]

i wonder how the shop tested your battery? Did they put it under load for Amps?
Ivan

[stownsen914]

Sounds like some possibly weird electric issue going on. A couple things I'd want to try:
- Load test the battery
- Disconnect the battery when the car is sitting, see if it still dies
- Try swapping in another battery, see if the issues go away

Sometimes batteries fail internally and give weird behavior, even intermittently.

[EC900]

If the battery is over 4 yrs old, I’d say replace it. Yes, load test it would show that it no longer holding the charge though showing 12.5v. A really dead, older battery won’t ever regain full charge and power will dissipate fast.

[dan88911]

You may want to check the door switches for the parasitic draw.

[COL911]

Don’t rule out intermittent alternator or voltage regulator issues. I had similar battery drain (10-11v) issues, but I could use the jump box to start; sometimes it would charge, sometimes not. 5 year old battery. New battery and alternator fixed it. Took me 3 months of trial and error to get things sorted.

[jwakil]

FYI the battery has been checked twice by Autozone and Orielly, and it’s 1 year old. After checking fuses, I see there is a small draw of 20mA from the fuse for the interior lights (4th fuse from left looking towards the fuse box). I’ve disconnected this fuse and will see if battery still drains. But what still puzzles me is why the alternator was not charging when I ran the car with a drained battery, and then came back to life after I trickle charged the battery?

[na2ub]

The alternator is more complex than you might think. I had a problematic alternator for years, before I had it rebuilt. I think there is even a circuit that runs to your alternator light, and if the bulb is out will cause problems charging. I wish I could be more specific, but if your battery is testing well, I would put my money on the alternator needing a new diode, or resister, or transister, or thermister or some other technical, electrical do-hicky.

I had mine rebuilt by a local alternator shop, but I think it cost close to just buying a new one.

Edit: I have the alternator with the built-in voltage regulator. Also, you should have a power draw, for, at least, the clock. Not sure if that is on the interior light circuit or not.

[Jeff Higgins]

What kind of a battery is it?

[jwakil]

Originally Posted by na2ub

The alternator is more complex than you might think. I had a problematic alternator for years, before I had it rebuilt. I think there is even a circuit that runs to your alternator light, and if the bulb is out will cause problems charging. I wish I could be more specific, but if your battery is testing well, I would put my money on the alternator needing a new diode, or resister, or transister, or thermister or some other technical, electrical do-hicky.

I had mine rebuilt by a local alternator shop, but I think it cost close to just buying a new one.

Edit: I have the alternator with the built-in voltage regulator. Also, you should have a power draw, for, at least, the clock. Not sure if that is on the interior light circuit or not.

I have removed my clock and I looked for any interior lights that could be staying on and only see the two above the doors and the one in front of glovebox and those are off. supposedly the radio is on the same fuse but that seems to be completely off as well.

[smadsen]

Check the glovebox light & switch. Not noticeable if it's on in the daylight. Also, is the frunk light going off when the lid is closed?

[jwakil]

Originally Posted by Jeff Higgins

What kind of a battery is it?

its this:

[Jeff Higgins]

Rats - standard AGM battery. There goes my easy answer. I've had lithium ion and lithium iron batteries that exhibit exactly the behavior you describe, wherein they "die" when sitting. They really don't, with the problem being they build internal resistance when sitting. The "work around" is to load them by turning on the headlights about five minutes before you try to start the car (or in my case, motorcycle) to break down that internal resistance and "wake them up". I've never heard of an AGM battery needing this, though, so it's probably not that.

[SpyderMike]

"But what still puzzles me is why the alternator was not charging when I ran the car with a drained battery, and then came back to life after I trickle charged the battery?"

I think the alternator is excited by voltage through the alternator warning light (as previously mentioned). Once excited the alternator should produce. You haven't mentioned if that warning light is turning on with key switch on but not to the start position.

[jwakil]

Originally Posted by SpyderMike

"But what still puzzles me is why the alternator was not charging when I ran the car with a drained battery, and then came back to life after I trickle charged the battery?"

I think the alternator is excited by voltage through the alternator warning light (as previously mentioned). Once excited the alternator should produce. You haven't mentioned if that warning light is turning on with key switch on but not to the start position.

The normal sequence is I turn the key and the light comes on and stays on after car is started. I hit the gas and after about 2000RPM the light will go off and then I see the voltage climb to 14V so I know alternator is activated. This is how it’s been since I’ve owned the car for 10yrs. However, the time in question I jump started the car, no lights came on and the voltage stayed at ~9V even after I revved the engine, so clearly the alternator was not activated. Also none of the dash gages were working.

[icarp]

I think your battery has a short inside . The AGM battery will shut itself down if the volts go below 11, I hate the agm batteries , 3 $400 ODYSSEY in my turbo none lasted more that 12 months
Total crap.
drain it to dead take it back to walmart

Ian

[jwakil]

Originally Posted by icarp

I think your battery has a short inside . The AGM battery will shut itself down if the volts go below 11, I hate the agm batteries , 3 $400 ODYSSEY in my turbo none lasted more that 12 months
Total crap.
drain it to dead take it back to walmart

Ian

I'm also suspicious of the battery but I thought the AGMs were the best non-lithium batteries you could buy. I'm a little weary of going to Lithium just due to the unknowns and requiring different trickle charger and if it can be jump started in emergency with regular battery, etc.

[Jonny H]

Originally Posted by icarp

I think your battery has a short inside . The AGM battery will shut itself down if the volts go below 11, I hate the agm batteries , 3 $400 ODYSSEY in my turbo none lasted more that 12 months
Total crap.
drain it to dead take it back to walmart

Ian

Meanwhile I have had an Odyssey PCA925 (28Ah) in my car for 4 years now. My car has electric AC and (prototype) electric heat so is under a constant load of at least 60A every time I drive it. Have never had the battery drain and have never used a trickle charger.

How? I have a decent modern alternator (one of our 175A units). QED