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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: 3882
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: 3149
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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2012 Porsche Carrera S
2016 Ford Edge 2.0
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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: 11108
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: 1679
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 Offline


Registered: 04/09/08
Posts: 12338
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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00 Jeep Cherokee
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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: 591
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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#3317801 - 03/20/14 07:55 AM Re: Battery completely dead ... but at 9V? [Re: Miller88]
Miller88 Offline


Registered: 04/09/08
Posts: 12338
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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18 Forester 2.5I Manual
00 Jeep Cherokee
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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: 577
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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