Mostly New Car Battery Drained. Still Charging For 24 Hours. Dead?


Old 05-19-12, 02:25 PM
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Mostly New Car Battery Drained. Still Charging For 24 Hours. Dead?

I have an 8AMU1R "SEALED, VALVE-REGULATED LEAD ACID" battery. From what I can tell, it's a Deka or East-Penn AGM battery just based on Googling the part number. My understanding is that if it says "Valve-Regulated" then that means AGM.

My car has a history of draining batteries. If the car isn't started every 2 weeks, it will drain the battery. My car was sitting in the garage for about 2 months and battery is definitely drained.

I removed the battery and hooked it up to my Schumacher SSC-1500A charger (2/10/15 Amp charger). It has options for "Standard / AGM / Gel" type batteries. Upon hooking it up to the charger, the charger when into a "Desulfation" mode for a few minutes before going into charge mode.

At first, I had it set to "Standard" since I didn't know I had an AGM. I let it run overnight and it never read more than 12.4 Volts (60%).

Now that I'm pretty sure it's an AGM, I changed the setting to AGM and let it charge at the 15A setting. It's been reading 12.5 Volts (63%) on the charger for the last hour without much change. At first it read 12.4 and then started flipping between 12.4 and 12.5. Now it's reading a constant 12.5 but still stuck on 63%.

This battery is less than 4 months old.

Did I kill my battery? Is there anything I can do to bring it back? Should I just keep letting it charge again overnight, but this time with the AGM setting instead of Standard?
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Old 05-19-12, 02:53 PM
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Any battery of that type (or any type) that sits in a discharged condition for any length of time is toast.

Once they drop below a certain'll never bring it back.

It might get enough of a charge to function for a while...but you'll be taxing your vehicle charging system.

Bet if you take it off the charger and let it sit for a day...the voltage will drop a lot.
Old 05-19-12, 05:20 PM
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I have AGM deep cycle battery in my TCH. It does take about a day to charge. That's deep cycle, baby, they take a lot in.

Now, here's the thing. You must use deep cycle chargers to charge those. Did you kill your battery with wrong setting? Have no idea. But I do know that you diligently saved receipt, and what you'll do next, is to go back and exchange it as "it is broke".
Old 05-19-12, 05:31 PM
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Thanks for the replies. Maybe I'll let it run overnight again with the AGM setting this time. If it gets fully charged, I'll let it sit for a day and test it again to see if it's holding the charge or not.

It's reading 12.7 volts now (65%). Up very little from when I posted last. That took about 3 hours to go up from 12.5 to 12.7 volts, and up from 63% to 65%.

Am I wasting my electric bill on this?
Old 05-19-12, 09:38 PM
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Well, I don't know if this is good or not.

It's still charging, the voltage on the charger is reading 13.1 Volts (68%).

When I disconnect the charger, it reads 12.57 with a digital multimeter but was steadily dropping 0.01 every couple seconds.

When I connected the charger in "Test Battery" mode, it read 12.5 Volts (75%). I don't know why it is giving different numbers while charging and different numbers in test mode.

The 75% full is the highest I've ever seen it. Yesterday when I was charging it with "Standard" battery type selected, it stayed around 50%-53% and got to 60% overnight but never improved past that. When I switched it to "AGM" battery type, it's been steadily climbing from 63% up to 68% but at a VERY SLOW rate, of about 1% per hour. Now it's reading 75% in test mode (not charging), which is the highest I've seen it yet.

I don't know what to make of all this, but I guess I will let it sit for a day after it's charged to see if it holds.

EDIT: I stopped the charger to test the battery with my multimeter. Now the charger has been started again and under charge, it's reading 15.3 Volts (88%). Confused!
Old 05-20-12, 03:59 AM
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Once you either get the battery charged or exchanged, you have other problems. They shouldn't discharge like you said in the OP. You have a drain within the car's system that needs attention. I have seen dome lights drain batteries fairly quickly when left on. Your alternator may be bad, too, so have it checked as well.
Old 05-20-12, 04:50 AM
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After 2 months sitting most batteries will lose charge due to computers, security etc. After 2 weeks is not normal unless you have a bad battery. How long has this 2 week story been happening, and how long have you had this battery. It all sounds to me that while there could be some kind of parasitic drain going on behind the scenes, most likely it is time for a new battery. You can check for typical causes from things like glove box light, trunk light, brake light switch sticking etc., but my guess is still your battery based on what you have told us. It also could be a mixture of causes including charging system instability. Did you completely check out all wiring connections around that yet also, especially grounds?
Old 05-20-12, 05:43 AM
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My GPS will kill a battery in about a week if I do not drive the vehicle.
Old 05-20-12, 07:24 AM
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1. stop wasting time anb running bill, exchange battery
2. mine is Panasonic AGM. It will show 13.8 fully charged on voltmeter
3. you will not be able to check deep cycle battery with voltmeter. I have good pals at local O'Reilly, they straight told me they do not have right tools to truly check on deep cycles.
4. there's a quite complex procedure and load test required to test deep cycles.
5. ergo, read #1

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