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AGM Batteries 12.8 or 12.9v instead of 12.7 ?? #4608804
12/19/17 10:10 PM
12/19/17 10:10 PM
Joined: Jul 2007
Posts: 4,261
Midwest USA
LoneRanger Online content OP
LoneRanger  Online Content OP
Joined: Jul 2007
Posts: 4,261
Midwest USA
"The sealed AGM and gel cell battery voltage (fully charged) will be slightly higher in the 12.8 to 12.9 range"
https://www.batterystuff.com/kb/articles/battery-articles/battery-basics.html#3


I thought there was no diff between flooded wet cells and absorbed glass mat (AGM) on parked engine and parasitics off, charge shown on the multimeter.



'09 Subaru Forester ...................(QS HM 5W30)
'16 Moto Guzzi Stelvio 1200 .....(ENI i-Ride PG 10W60)
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4608819
12/19/17 10:21 PM
12/19/17 10:21 PM
Joined: Mar 2015
Posts: 5,100
Virginia
bbhero Offline
bbhero  Offline
Joined: Mar 2015
Posts: 5,100
Virginia
Nah the AGM batteries will having a higher open voltage than a comparable flooded battery being both are truly 100% state of charge.


Last edited by bbhero; 12/19/17 10:22 PM.

Nissan Altima 3.5 Coupe
Quaker State High Mileage 5w30 Purolator Boss 14610
"Treat your family like your friends and treat your friends like your family."
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4608822
12/19/17 10:22 PM
12/19/17 10:22 PM
Joined: Aug 2006
Posts: 9,839
Central Washington
Colt45ws Offline
Colt45ws  Offline
Joined: Aug 2006
Posts: 9,839
Central Washington
Yes, this is true, they have a higher OCV. They also prefer a higher charging voltage.


-Colton
2002 Ford Crown Vic PI 207k, Ex-Kootenai County, ID Unit #42
Down for engine swap
2003 Ford Crown Vic PI 75k
Castrol EDGE HM 5W30, Fram XG2
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4608957
12/20/17 06:07 AM
12/20/17 06:07 AM
Joined: May 2013
Posts: 2,094
Saskatchewan, Canada
Johnny2Bad Offline
Johnny2Bad  Offline
Joined: May 2013
Posts: 2,094
Saskatchewan, Canada
A fully charged lead-acid battery will show 2.2V per cell (6.6V on a "6 Volt" battery and 13.2V on a "12 Volt" battery).

The 12.7~9 V/AGM reading they refer to in the OP's article is after a load has drained part of the charge.


'57 FL Straight 50 wt
'90 Miata 1.8L w/Rotrex Supercharger [Mobil1 0W-40]
'96 Ram 1500 [3.7L Mobil1 0W-20 / 1L 15W-50]
'01 PT Cruiser [Mobil1 0W-40]
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4608995
12/20/17 07:07 AM
12/20/17 07:07 AM
Joined: Jul 2007
Posts: 4,261
Midwest USA
LoneRanger Online content OP
LoneRanger  Online Content OP
Joined: Jul 2007
Posts: 4,261
Midwest USA
Wouldn't 13.2v be the initial surface charge which bleeds off few minutes after removing a charger/maintainer, and the AGM battery then settles at 12.9?



'09 Subaru Forester ...................(QS HM 5W30)
'16 Moto Guzzi Stelvio 1200 .....(ENI i-Ride PG 10W60)
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4609179
12/20/17 10:50 AM
12/20/17 10:50 AM
Joined: Dec 2016
Posts: 2,177
VA
maverickfhs Offline
maverickfhs  Offline
Joined: Dec 2016
Posts: 2,177
VA
Usually I have seen AGM stays between 12.75-13V. My current Yuasa AGM, stays at 13V even after a few days tender is removed, measuring from cheap HF multimeter though.

While lead acid ones I have seen between 12.4-12.6 after it has been fully charged, and tender is removed. These voltage varies based on the age of battery too.

All for motorcycles.


2006 Civic EX 202K/AT
2006 Acura TSX 180K/AT
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4609187
12/20/17 10:57 AM
12/20/17 10:57 AM
Joined: Jun 2003
Posts: 5,926
Illinois
SHOZ Offline
SHOZ  Offline
Joined: Jun 2003
Posts: 5,926
Illinois
The specific gravity of the electrolyte is higher in AGMs than a flooded battery. That is most of the gain in voltage.

Usually in the 1.315 range when finished and fully charged.


2008 Hyundai Accent 1.6L 5 sp manual hatchback
2010 Hyundai Genesis Coupe Track 2L Turbo 6sp manual
Re: AGM Batteries 12.8 or 12.9v instead of 12.7 ?? [Re: LoneRanger] #4609233
12/20/17 12:05 PM
12/20/17 12:05 PM
Joined: Oct 2017
Posts: 203
A Highway Near You
PiperOne Offline
PiperOne  Offline
Joined: Oct 2017
Posts: 203
A Highway Near You
The AGM banks in our trucks when properly charged settle out at 12.8 to 12.9. We basically charge at 14.7 and float at 13.8 on the charger, alternators temp compensate and will run between 13.5 and 14.9.


HDEO in Diesel Engines. No spark plugs here.

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