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Have I lost 20% of my new batteries capacity?

RVLiFe

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Jun 14, 2021
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I have a new 206Ah SOK battery. It has recently started to exhibit what appears as voltage drop. Is this normal or should I be concerned. SOK says it’s normal and sometimes happens. Sometimes?

I charged it to 14.6V 44hours ago. I have a small parasitic draw on it due to my RV’s leveling gear/controller and TPMS repeater of approx .08 - .09 Amps. My battery is showing 13.3Volts remaining and the SOC charts all show this to be around 80% capacity. This battery used to settle closer to 13.55 volts after a couple of days.
Any thoughts?
 

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LiFePo4 batteries will settle to about 3.3 to 3.4 volts per cell after charging, if you just let them set without a load. 13.3v is pretty much in the ballpark of what I would expect for a 4 cell battery.
 
14.6V is 3.650V per cell which is above the working voltage range for LFP which is effectively 2.900-3.450.
You can charge cells to 3.650 and fully saturate them till the pack takes less than 1A charge, and within 2 hours of no charge the cells WILL SETTLE down. Depending on Actual Grade that could be anywhere from 3.500 to 3.400. In fact it is NORMAL for LFP to settle from Hi Voltage. The term "knee's" if often used, that refers to the sharp drop or rise of the voltage curve which occurs below 2.900 and above 3.450 and that only represents about 3% of the Gross Capacity of teh cells.

Form Normal Runtime while maximizing lifespan, folks usually charge to 3.500 and then float allowing the cells to level up and reach saturation.

In my Signature is a link to the LFP Voltage Chart showing the curve etc... If you download the PDF it is Hi Rez.

Here is the Charge Profile I use for my SCC & Inverter (almost identical). This may be helpful to you as well.
All equipment MUST BE Voltage Corrected & Calibrated (VERY IMPORTANT) see link in my signature on how to do it.
Divide Values X2 for 12V. Multiply X2 for 48V.
Absorb: 28.2 for 15 minutes (3.525vpc) (some call this boost)
Equalize: OFF
Float 27.9V (3.4875vpc)
MIn Volts: 22.0 (2.750vpc)
Max Volts: 28.7 (3.5875vpc)
Rebulk Voltage: 27.7 (3.4625vpc)
End Amps: 14A (*1)

(*1): End Amps is calculated from the Highest AH Battery Pack in a Bank. IE: 200AH X 0.05 = 10A 280AH X 0.05 = 14A.
NB: Victron Forum discussion says EndAmps = TailCurrent
This get's the bank charged to full with high amps (Constant Current) and then float (Constant Voltage) tops off so the cells are on average between 3.475-3.500. I am running 7/24/365 so float is used up by the Inverter + provides whatever the packs will take to top off.

** Coulumbic Efficiency for LFP is 99%

Hope it helps, Good Luck.
 
LiFePo4 batteries will settle to about 3.3 to 3.4 volts per cell after charging, if you just let them set without a load. 13.3v is pretty much in the ballpark of what I would expect for a 4 cell battery.
I guess I expected closer to 3.4V per cell. 3.3V seems a little low for the supposedly grade A cells that SOK claims. It just seems that the voltage changed in me from how it used to behave so I was concerned that I may have an issue. My amperage draw is minimal <5Amps so it appears that I’m still getting the capacity but I’ll soon be connecting an inverter to the battery so I’ll see if that has any negative impact as well.
 
I guess I expected closer to 3.4V per cell. 3.3V seems a little low for the supposedly grade A cells that SOK claims. It just seems that the voltage changed in me from how it used to behave so I was concerned that I may have an issue. My amperage draw is minimal <5Amps so it appears that I’m still getting the capacity but I’ll soon be connecting an inverter to the battery so I’ll see if that has any negative impact as well.
norminal voltage is 3.2, all lifepo4 will eventually settle to that voltage, you battery seems quite all right
 
LFP Full Voltage Range is 2.500=3.650 but the Chemistries "Working Voltage" is 2.900-3.450, these TWO things confuse people far too often.
This below will likly Enlighten.
1635089247636.png
hope it helps.
 
So I can wait some hours resting before I set the my smartshunt to 100%? (like the TS has also)
 
The SmartShunt should reset itself to 100% when appropriate if you have it setup correctly. There is no need to do it manually under normal circumstances.
 
First of all the shunt needs to know what is 100% It is measuring it using the peukert exponent. It should be set to 1.05 according Victron. My reply was when it should be at 100% because it also is looking at voltage
 
LFP Full Voltage Range is 2.500=3.650 but the Chemistries "Working Voltage" is 2.900-3.450, these TWO things confuse people far too often.
This below will likly Enlighten.
View attachment 69978
hope it helps.
That’s great information to understand the difference between the voltage to expect after a LiFePO4 cell has been allowed to ‘rest’ for a while versus the voltage to expect when even the smallest amount of discharge has begun, but is there similar information anywhere about the difference between voltage while charging and rest voltage?

Obviously the difference would depend on charge current, but I’m thinking about the difference to expect between Float Voltage maintained at infinitesimally small CV charge current while the sun is up and the SCC is active and the voltage to expect after the sun has gone down and the cell has been resting for an appropriate period (1-12 hours).
 
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