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dgmar-ni avatar image
dgmar-ni asked

Low battery alarm but DOD over 90%

Good day,

A system that triggers low battery alarm and it has new batteries that have a high SOC. Last night it turned off suddenly. Here you are pics of the alarm log showing the time (00:35:13) and also the SOC: (90% at 23:55)

1706798777297.png

What can be happening in this case? Any help will be appreciatted.

SOClow battery warning
1706798777297.png (317.6 KiB)
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snoobler avatar image snoobler commented ·
Please provide more information.


I can't imagine a battery at 47V being at 90% SoC.


What battery?


What device is reporting SoC?


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dgmar-ni avatar image dgmar-ni snoobler commented ·

The system has been renewed with a battery bank 24 units AGM 220Ah 12V (BAT412201084).

The system has two Quattros 5kVA 48V and the batteries have been monitoring with the BMV-702. I am not sure if the battery meter needs calibration or I am missing a parameter that is not properly adjusted.

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snoobler avatar image snoobler dgmar-ni commented ·

you have 24 AGM batteries?


I assume you have a 4S6P configuration?


That's 1320Ah @ 48V or 63.3kWh


You need AT LEAST 132A of charging to properly charge those batteries.


To charge these batteries to full with a PV array in a day, you would need about 15-20kW of PV and very good solar conditions.


AGM batteries at less than 48V are at an extremely low state of charge. They are NOT anywhere near 90%. The BMV may be set incorrectly, and a false sync has occurred.


Batteries used at low states of charge sustain irreversible damage. It's important that they are charged to full daily or as close to daily as possible.


You can be confident that they are fully charged when they have achieved 56.8-58.4V and the charge current has dropped to 26A.


It's also critically important that all of the individual 12V be at near identical voltages when the system is at peak voltage (!57.6V) and that NONE of them are over their rated voltage (14.6 preferred, 14.9 absolute).


I recommend you check all 24 12V with a voltmeter and document the values. You may find that you have one or more batteries that are reading drastically different than the others.


You are destroying your batteries. You urgently need to charge these batteries by any means possible.


Also, recommend you post your BMV settings and document your available sources of charging.



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dgmar-ni avatar image dgmar-ni snoobler commented ·

Yes that is correct you're right to state that the batteries are very discharged and they need to recharged as soon as possible. Currently the system has controllers one MPPT 450/100 and one MPPT 150/100 but this last one is damaged and I will look for a replacement. The MPPT 450/100 is currently running but is not enough to recharge the battery bank as it before with both controllers.

But yes in spite of the batteries are discharge I don't understand why the SOC shows 90%.

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snoobler avatar image snoobler dgmar-ni commented ·

It is not configured properly.


1706819434152.png

When charging with solar, inconsistent performance may trigger false sync.

Do you have access to grid or generator? If so, you need to utilize it immediately.

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dgmar-ni avatar image dgmar-ni dgmar-ni commented ·

One thing with the inverters is that the Phase 1 is 5 years old:

1706813166734.png

Phase 2 has been recently replaced with a new unit.

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snoobler avatar image snoobler dgmar-ni commented ·

This may be relevant, but probably not.

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pwfarnell avatar image pwfarnell dgmar-ni commented ·
What settings do you have in the BMV, if they are wrong you may get the SOC resetting to 100% before they are fully charged from solar and then you think they are fuller than they really are.
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dgmar-ni avatar image dgmar-ni pwfarnell commented ·

Hello @pwfarnell. These are the settings on BMV:

1706814516596.jpeg

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pwfarnell avatar image pwfarnell dgmar-ni commented ·
Your BMV will reset to 100% SOC if your voltage goes above 55.2V and your charge current is below 52.8A( 4%x1320Ah). As you are short of solar at the moment you may well have achieved these conditions not because the batteries are charged full but because you do not have enough solar. Therefore you are now running with batteries that are under charged. Set the charged voltage (tension de la batteria cargada) to 56.8V and the tail current (corrienta de cola) to 2%. This will mean the SOC only resets once the batteries are full. Then you need to find a way to fully charge the batteries as soon as possible.
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dgmar-ni avatar image
dgmar-ni answered ·

Good day,

The system has been charging in parallel solar with the grid (in spite the grid is not reliable one phase drops under 90V AC) but it is close to reach 56.6V:

1707158877426.png


I have a question if you can answer about the solar charger as only one string has power. Is not a problem of loosed connection or bad MC4:

1707159799366.png


No signal of smoking or burned on connection ports for PV1 or PV2 inside the controller.

Any clue?


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