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Old 01-14-2020, 03:30 PM   #1
sunshine 1
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AGM battery SOC

I have 3 Duracell deep cycle AGM batteries 105 Ah each. I have been careful to not let them go under 50% SOC. I thought that was 12.06 volts according to some websites, but lately I have been seing other web sites saying 50% SOC was 12.2 volts for AGM batteries. Which one is it???
 
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Old 01-14-2020, 04:19 PM   #2
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Your specific battery should have a spec sheet available online that will provide you with its charge curve. In addition just for information purposes SOC is the least accurate means of measuring your batteries capacity. While AGM and FLA batteries have a steeper charge curve SOC is still and estimation based upon battery voltage. This is nearly impossible to do with lithium batteries as the charge curve is so relatively flat.



Keeping track of actual AH in/out is a far more accurate means of measuring your batteries SOC/DOD. In order to do that users generally install a shunt and make sure that all loads are connected downstream of the shunt.
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Old 01-14-2020, 06:37 PM   #3
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I am interested in making sure my high dollar AGM batteries last a long time if that is the subject of this thread but your losing me with all the abc acronyms. Can you explain in simple terms what your talking about and how to monitor same please.
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Old 01-14-2020, 06:42 PM   #4
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FLA=Flooded Lead Acid
SoC== State of Charge
DoD -- Depth of Discharge
AH ==Ampere hours

ABC== first 3 letters of alphabet
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Old 01-14-2020, 07:50 PM   #5
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Quote:
Originally Posted by jeffba View Post
FLA=Flooded Lead Acid
SoC== State of Charge
DoD -- Depth of Discharge
AH ==Ampere hours

ABC== first 3 letters of alphabet
not just the definitions. Need an explanation of what to do in laymans terms.
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Old 01-14-2020, 08:20 PM   #6
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State of charge (SoC) is the level of charge of an electric battery relative to its capacity. The units of SoC are percentage points (0% = empty; 100% = full). An alternative form of the same measure is the depth of discharge (DoD), the inverse of SoC (100% = empty; 0% = full). SoC is normally used when discussing the current state of a battery in use, while DoD is most often seen when discussing the lifetime of the battery after repeated use.



AH is a unit of electric charge, having dimensions of electric current multiplied by time, equal to the charge transferred by a steady current of one ampere flowing for one hour.
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Old 01-14-2020, 08:31 PM   #7
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I have tried to find a spec.sheet of the batteries, I believe they are made by East Penn Manufacturing. I guess I could call them and ask.
I don't have a battery monitor and shunt.
I just try to get some help here, but evidently not.
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Old 01-15-2020, 06:38 AM   #8
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To really know what state your batteries are in you need to set up a battery monitor. The simple voltage light system that come in the rigs only gives a rough approximation.

Battery monitors are relatively inexpensive and one of the first additions you want to add when you consider boondocking.
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Old 01-15-2020, 06:50 AM   #9
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Sunshine 1 I think everyone on the thread is trying to help you. Perhaps just knowing that the state of charge lights are an approximation may be enough for you to manage.
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Old 01-15-2020, 07:48 AM   #10
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Okay, thanks guys. I have been thinking about getting a battery monitor. Will the battery monitor give you the SoC percentage of your batteries, not only the voltage? I have the victron solar charger which tells me the voltage going from the controller to the battery. I understand that is not the real state of the battery.
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Old 01-15-2020, 09:03 AM   #11
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Sunshine if you already have a Victron solar charge controller I would highly recommend picking up a BMV-712 battery monitor. There are cheaper battery monitors available however the Victron integrates seemlessly with other Victron equipment and the BMV comes with a built in output relay that can be programmed to perform a plethora of actions that may be useful to you as you learn more. The BMV will display voltage, current as well as SOC. It also displays total amp hours in/out.
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Old 01-15-2020, 02:11 PM   #12
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Until DW purchased her 2016 Mini Countryman S All4 the other day, I had little concern about AGM batteries. I found the battery after much poking around and discovered it is a BMW AGM battery. The numbers on it make little sense to me other than the 760CCA and the Ah rating. Thinking of replacing the 4 year old battery and have now discovered that the new one will need to be "coded" when installed - an $85 job by a service shop. The car charging system is just too danged smart - it monitors age, miles, voltage, amps, etc. to temper the charge of the battery. Without "coding" it will not charge the AGM replacement correctly. There is literally a ton of info out there. I started at https://www.knowyourparts.com/techni...agm-batteries/. Also found this useful... https://autofthings.com/agm-vs-stand...tery-charging/
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Old 01-15-2020, 03:46 PM   #13
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PNW Fireguy, I have a Victron smart solar 100/50 with the bluetooth app. I have been thinking about getting the BMV-712, but it is not cheap over $200.
Besides I am not sure how to connect it to the negative side of the battery via the shunt.
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Old 01-15-2020, 05:50 PM   #14
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What I was wondering is if allowing a battery to discharge below a certain percent of charge repeatedly is a bad thing? All these acronyms are just making it more confusing.


Do I need to get a battery monitoring system if I was on the road a lot and using the batteries for the fridge?
Are AGM batteries more likely to have issues with deterioration due to wide swings in charge %? I thought these high dollar batteries were several steps better than lead acids?
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Old 01-15-2020, 06:00 PM   #15
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AGMs are the same basic chemistry as lead acid. There is not water to add and they do not leak.

Like lead acid, they do not have a sense of humor if you discharge them too far.
The big plus is they do not require maintenance and can be installed on their side.

My replacement batteries will be Li
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Old 01-15-2020, 06:02 PM   #16
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Not sure this helps or hurts, but this link has some good charts showing capacity fade and DoD.

https://www.google.com/search?q=batt...I9pSZcTWRwWyM:
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Old 01-15-2020, 06:58 PM   #17
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Sunshine 1 the BMV-712 would be an excellent compliment to your existing solar controller. You would be able to use the Victron Connect application in a smart phone to monitor both devices. There are several YouTube videos depicting how to hook the BMV

Https://YouTube.be/tv055vmZgvy
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Old 01-15-2020, 07:03 PM   #18
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Just to expand on what has already been put forth by Jeffba...AGM and flooded lead acid (AGM/FLA) are not very forgiving when discharged below 50% of their rates capacity. They also like to be kept at full charge. For those two reasons it’s a good thing to know what your capacity is and how much you discharge the batteries. This is where the battery monitor comes into play to accurately measure and track both of those quantities. If you want to get the most out of your battery investment knowing those two items is critical.
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Old 01-15-2020, 07:05 PM   #19
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Sunshine 1 if you plan on attending the west region MOC rally I will help you install your BMV.
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Old 01-15-2020, 07:30 PM   #20
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Quote:
Originally Posted by mtlakejim View Post
What I was wondering is if allowing a battery to discharge below a certain percent of charge repeatedly is a bad thing? All these acronyms are just making it more confusing.


Do I need to get a battery monitoring system if I was on the road a lot and using the batteries for the fridge?
Are AGM batteries more likely to have issues with deterioration due to wide swings in charge %? I thought these high dollar batteries were several steps better than lead acids?
Jim,

Your truck will keep your batteries up as you travel or you can shut the fridge down for 8 hours or so and it will still stay cold. How big is your battery bank?

The battery monitor is primarily a boondocking tool.

These are relatively inexpensive batteries compared to Li.
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