question

Milos Plechlo avatar image
Milos Plechlo asked

Victron lithium superpack loose max SOC by 3% each day

Hi,

after several weeks after installation, my new battery does recharge to 3% less SOC as day before. There are sufficient conditions, enough solar power, but the max SOC is less and less. It is linear decrease. Twice I did manual reset to 100% trough BMV, once it recharged to 100% automaticaly, but now I have only 80% after recharge and this starts sigificantly limit my installation and usable power form battery during the night.

Lithium superpack 60Ah, Smart MPPT 100/20, Multiplus 800VA 12V with ESS - optimized with baterry life mode, BMV712

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SOCSuperPack
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3 Answers
pwfarnell avatar image
pwfarnell answered ·

Your BMV712 settings may not be correct so they are not counting your recharge correctly. Can you post a screenshot of the BMV settings in the Victron Connect app and confirm what absorption voltage the MPPT is set to.

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Milos Plechlo avatar image Milos Plechlo commented ·


These seetings have worked well 1 and 1/2 month after installation. Then the SOC has started to decrease each day ...

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pwfarnell avatar image pwfarnell Milos Plechlo commented ·
Your settings all look correct so it is not under counting of the charge by the BMV 712.

Looking at your graph it appears that you are not getting up to 14.2V on the battery voltage so you may not actually be fully charging from your solar. you would need to chevk the graphs on a shorter time scale to confirm this. Does the MPPT go.into oat or stay in bulk.

When you say the system worked for a while makes me think that you are now getting into autumn and you are collecting less solar power. Are you in the northern hemisphere.

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Milos Plechlo avatar image Milos Plechlo pwfarnell commented ·

Hi, thanks for your advices, but:

I am getting 14,2V and 1h absorbtion, then switch to Float voltage at 13,5V. There is enough solar power, bulk charge was at full allowed 20A some days, but finishing at less and less SOC. If there are poor solar conditions it is OK that I cannot achieve full or suficient charge, but from monthy trend you can see that this is not the case of solar conditions. They are metmost of the time, but despite of this SOC decreases by 3% each day. I can now manualy synchronize to 100% od SOC, but the situation will repeat in same way :(


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JohnC avatar image
JohnC answered ·

@Milos Plechlo

This is adjustable via the Charge Efficiency Factor. Your 95% is too low. Try 99% and work from there.

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Milos Plechlo avatar image
Milos Plechlo answered ·

Hi, what is the meaning of this factor? I am not ok with changing any setting if system was working last month, but I can try. This week is very sunny forecast so I will wait few days first before any change of parameters.

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JohnC avatar image JohnC ♦ commented ·
@Milos Plechlo

The CEF determines how much energy is credited to the SOC as 'useful'. 95% is the default for Pb batteries, and Victron actually recommend 99% for Li's anyway.

The Peukert Exponent is used in a similar way when discharging. This is a little more difficult to grasp, and 1.05 won't normally affect things much under typical loads. But with a serious load applied, efficiency drops.

The default settings err on the safe side usually. But now you've spotted the drift (and don't like it), the options are there to tune it properly. Maybe time to read the manual, hey.. :)

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Milos Plechlo avatar image Milos Plechlo JohnC ♦ commented ·
Hi John, thanks for explanation. I have changed the CEF to 99%. Will see tommorow what will be the effect.
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Milos Plechlo avatar image Milos Plechlo Milos Plechlo commented ·

Today noon done auto synchronization to 100%. Will see next days if CEF was the cause :)


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