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#3316247 - 03/18/14 08:55 PM Battery completely dead ... but at 9V?
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Went out to my Cherokee today to try to continue playing around with the broken ujoint strap bolt.

I noticed my drivers side rear door was open. Battery was dead. The headlight switch was in the parking light position and interior lights were set to on.

So, obviously nothing happened.

I pulled the battery out and it still have 9V?

It's also having some issues taking a charge.

Shouldn't something at least happen with 9V? I'm wondering if the local lowlives also screwed up my electronics.
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#3316251 - 03/18/14 08:58 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
redbone3 Offline


Registered: 06/09/12
Posts: 185
Loc: Reno, NV
You are measuring 9V with no load. Measure the voltage under load and it is probably a whole lot lower. With the battery in the car, you can turn on the headlights and see a big drop in voltage.
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#3316254 - 03/18/14 09:01 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Nothing happened with headlights turned on or cell phone charger plugged in.

No dome light either.
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#3316261 - 03/18/14 09:08 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Donald Offline


Registered: 03/21/04
Posts: 13495
Loc: Upstate NY
Some of these items may be controlled by relays that won't kick in at 9V.

Charge it with a plug-in charger than have it load tested. Check the cells for low battery acid level.

How old is the battery?

Some fancy chargers will not charge a very low voltage battery.
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#3316281 - 03/18/14 09:25 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
123Saab Offline


Registered: 10/27/10
Posts: 1298
Loc: PA
Dead cells can reduce the amps so it wont do much but still show some volts.

It's dead most likely.
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#3316282 - 03/18/14 09:25 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
jeepman3071 Offline


Registered: 04/15/10
Posts: 1721
Loc: Storrs, Connecticut
Did you leave the door open or did someone force their way in?

Once the battery gets discharged enough, it can refuse to take a charge. Anything that low will result in weird things happening with the electronics. I had a dead cell in my battery, and all the gauges went crazy in my Jeep and it would run for 2 seconds and shut off. Chrysler electronic systems seem to be sensitive, and I think you might need a new battery. frown

How old is the battery?
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#3316285 - 03/18/14 09:29 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
morris Offline


Registered: 08/24/08
Posts: 3681
Loc: ks, wichita
i am not an electronics engineer. BUT i have learned that electronics chips if the needed voltage is not sent to them they CAN act very strangely. so if one just stops be glad.

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#3316290 - 03/18/14 09:33 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Chris142 Offline


Registered: 06/05/03
Posts: 11369
Loc: apple valley, ca
A 12v car battery is considered discharged at around 12.2volts. 9v is way dead.
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#3316299 - 03/18/14 09:39 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Battery is less than two years old.

I left it unlocked. That way the locals will just open it up and not break into it.
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#3316307 - 03/18/14 09:43 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
901Memphis Offline


Registered: 08/14/10
Posts: 5672
Loc: Northern Kentucky
9v is extremely dead. Anything under 10.50v is basically flat. A fully charged battery with no charge or discharge for 6+ hours would be at least 12.60v or higher.

Get that battery charged before the damage gets worse, they don't like to go that low but it should recover fine. You may need a special charger to get it charged since it went so low. You can take it by an auto parts store for a quick charge or take this as an opportunity to buy a new charger.
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#3316314 - 03/18/14 09:49 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Electrolyte levels are good and it didn't freeze.

Up to about 10.6 volts. I have it on the 2 amp charge. I try to avoid 6 amp charge.


Edited by Miller88 (03/18/14 09:49 PM)
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#3316335 - 03/18/14 10:02 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
JHZR2 Offline



Registered: 12/14/02
Posts: 33698
Loc: New Jersey
Classic shorted cell. No practical energy as the battery discharges into it, but yet open circuit reflects the chemistry on the other cells.

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#3316347 - 03/18/14 10:13 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Likely put another battery into it frown

Nothing like a $500 month on vehicle repairs.
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#3316369 - 03/18/14 10:30 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Rolla07 Offline


Registered: 11/05/11
Posts: 1718
Loc: MTL, CANADA
Where do you live?!! My city its hit and runs!! Always something...
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#3316414 - 03/18/14 11:36 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Barkleymut Offline


Registered: 01/27/04
Posts: 2432
Loc: Richmond, VA
Google tells me that he is very close to Syracuse NY
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#3316444 - 03/19/14 12:58 AM Re: Battery completely dead ... but at 9V? [Re: Miller88]
MNgopher Offline


Registered: 09/17/02
Posts: 2969
Loc: Lakeville, MN
9V is way dead. Anything under 12V is pretty well dead, and you should be planning on buying a new battery. Our previous 88 Cherokee did the same thing. Left a door slightly open, lights on all night, and dead as a doornail. The battery limped on for two months, then kicked the bucket.

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#3316626 - 03/19/14 08:41 AM Re: Battery completely dead ... but at 9V? [Re: Miller88]
rshaw125 Offline


Registered: 08/18/04
Posts: 2519
Loc: Raleigh ,NC CSA
Put it on a 2 amp charge for a day. Remember the alternator is not designed to charge a dead battery. Drive it and then check voltage with engine off. Should be around 12.75 volts if fully charged.
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#3316732 - 03/19/14 10:21 AM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Vikas Offline


Registered: 07/22/05
Posts: 8140
Loc: NorthEast
I think the guys who did that want your NEW battery!

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#3316810 - 03/19/14 11:08 AM Re: Battery completely dead ... but at 9V? [Re: rshaw125]
wrcsixeight Offline


Registered: 10/15/10
Posts: 1030
Loc: california
Originally Posted By: rshaw125
Put it on a 2 amp charge for a day.


The vehicle in question probably has a ~75 amp hour battery.

10.5 volts is considered 100% discharged. If the battery in question were still healthy, at still near full capacity when it was drain to 9v, it would require anywhere from 110 to 125% the energy removed from it. Lets say 125%

94 amp hours 94 amp hours divided by 2 amps is 47 hours.

If the charger used does not recognize the battery because of the 9v factor, the battery should be paralleled to a known good battery and then charged until its resting voltage is high enough that the charger will recognize it..

Since the battery in question is likely has nowhere near full capacity remaining, a day at 2 amps might be enough to bring it near full charge.

If this theoretical 2 amp charger does not raise the voltage into the mid 14's it is likely it will never
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#3316937 - 03/19/14 12:21 PM Re: Battery completely dead ... but at 9V? [Re: Barkleymut]
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Originally Posted By: Barkleymut
Google tells me that he is very close to Syracuse NY


Yup. I live in the city of Syracuse. A mini detroit. Per capita, we have worse crime!

Anyway, I let it until the morning. Then let it sit for a while and checked voltage. 12.6.

That's higher than what it is after the Jeep sits for a few days. I have some parasitic draw that I need to get sorted out. It'll kill a battery on its own if left for 2 or 3 weeks.

I'm going to continue charging it. I'm sure I *could* have jumped it off of the Focus, but if it's that low, I don't want to risk the 14 year old alternator.

I'm going to let it charge at 2 amps overnight again and see what happens.
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#3317379 - 03/19/14 07:47 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
redbone3 Offline


Registered: 06/09/12
Posts: 185
Loc: Reno, NV
Originally Posted By: Miller88
Electrolyte levels are good and it didn't freeze.

Up to about 10.6 volts. I have it on the 2 amp charge. I try to avoid 6 amp charge.


6 amps won't hurt anything and it will charge faster.
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2014 Passat Wolfsburg, 1995 Miata.

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#3317801 - 03/20/14 07:55 AM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Miller88 Online   content


Registered: 04/09/08
Posts: 6590
Loc: Onondaga County
Let it do the 6 amp charge for 6 hours last night. Getting there! It's holding voltage higher than it does in the Jeep. Hopefully letting it run again tonight on the 6 am charge I'll be fully charged.
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#3320160 - 03/22/14 07:49 PM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Da Game Offline


Registered: 12/27/05
Posts: 550
Loc: Chicago
Here is one from Associated Equipment that will recharge a battery down as low as 1v. Thats the override switch.

http://associatedequip.com/product/model-9640/

This Interacter will charge also as low as 1v.

http://interacter.com/products/industrial-commercial-series-specs/

Both made in the USA.

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