Battery is peramanty not loading - DC Voltage high

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schwuppe asked May 11, '24

Battery is peramanty not loading - DC Voltage high

Hello

I have a Victron Multiplus-II and a 16s 280Ah LiFePo Battery. I did not manage to get the system running, so I remove all components and add it one by one.

Settings:

-I have now disconnected the BMS bus communication and let the MP do the work.
-DVCC is off, ESS is set to optimizd w/o battery life
-I have set up MP as battery monitor. What does it mean if I select nothing here?

Problem:

-The BMS tells me a SOC of 60% which is plausible to me
-The BMS tells me a Voltage of 52,9V, this is also readout via multimeter.
-When I measure the battery outlets I get 60V.
The value is /system/0/Dc/Battery/Voltage

Why is there such a big discrepancy and why does MP detect a SOC of 95%?

Multiplus-II

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schwuppe commented · May 11 at 09:55 AM

DC voltage looking like this:

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1715421342517.png (14.6 KiB)

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Answer 1 · 2024-05-11T11:50:47Z

Alexandra answered · May 11 at 11:50 AM

@schwuppe

The MP doesn't have a shunt so the SOC is more a guess.

95% is probably where your soc when bulk is finished is set. And there is nothing going to the batteries. So the assumption of the 95% is probably based on that.

Did you measure the DC terminals on the inverters?

For the feedback to happen, the dc bus has to be higher and therefore will be a more ready source to send power back when you are feeding back.

If you dont want it too high try cap it in DVCC. But it seems like the batteries are fine and happy. So dont think there is a problem there.

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schwuppe commented · May 11 at 02:32 PM

I am measuring DC voltage at the cable from MP to battery, and inside the battery from first to last cell.

Now I have set the absorption voltage to a low value of 56V in the MP to be sure that the BMS is not breaking etc. The values there are higher.

Now, BMS is configured back. It has 64% SOC but it is loading slowly with a few A pulsing to 0A.

I do not see my misconfiguration. It should load with 500W.

-What I also do not understand MP voltage goes slightliy abouf 56V to ~56,6V and them immediatelly drops towards bat. voltage of 53V.

And why is the inernally measured voltage of the cells not increasing to the outer MP voltage?

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Answer 2 · 2024-05-11T16:50:22Z

madmaxx answered · May 11 at 04:50 PM

Your first picture states that "Has DC system" is disabled. I don't own your product. Could it be that this switch is the switch to enable the DC charging component of your device?

If you divide 60V by 16 batterie you arrive at a voltage of 3,76 Volt per battery which is beyond the recommended maximum voltage. Something in your system shuts off charging correctly, maybe your BMS.
Your system is supposed to switch over to constant voltage charging at 3,65 volt per cell, but not to go to 3,76 volts. May be you configurd it incorrectly.

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schwuppe commented · May 11 at 09:57 PM

I have only the Battery, so I think it is correct to disable has dc system.

I dont know where to setup 60V, my absorption Voltage was at 57,6V at this time.

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Answer 3 · 2024-05-11T16:55:24Z

Matthias Lange - DE answered · May 11 at 04:55 PM

It looks like a blown fuse or loose connection somewhere between the MultiPlus and the battery.

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Answer 4 · 2024-05-11T21:44:32Z

schwuppe answered · May 11 at 09:44 PM

Discharging works well, also with higher current. Maybe I'll try to short the BMS directly connect the victron to the Cells.

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Answer 5 · 2024-05-12T05:21:08Z

Paul B answered · May 12 at 05:21 AM

Check the batteries cell voltages. You may have one cell that's not balanced yet. If the bms is connected correctly to the cerbo. Then it will tell the multi to stop charging at a lower figure as one cell is full even those others are lower. It will take time for the bms to balance the cells. Do not remove the bms or yomay damage a battery cell from overvoltage.

Check all cells and make sure none go over 3.65v there about.

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Answer 6 · 2024-05-12T06:39:18Z

schwuppe answered · May 12 at 06:39 AM

the cells are ok

1715495948024.png (22.5 KiB)

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Sten commented · May 12 at 07:10 AM

You have to look at your cell voltage when the battery is in absorption.

You can't se if cells are unballanced under discharge.

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