MultiplusII - ignore AC and SOC

DIY
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1

Howdy, hoping for some guidance/explanation on what I’m seeing.

Victron system in my RV. 50A grid connection always connected. (4) 24v100ah LiFePo4 batteries in parallel, MPPT, solar panels, Cerbo GX, Victron BMS, Multiplus-II, etc.

System works fantastic for off grid use. Now that summer is hitting, I have been tweaking the system to prioritize the batteries and solar as much as possible before switching to grid.

As it sits:

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Batteries are fully charged. Running off batteries and ignoring AC as expected.

VEConfig set as follows:

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The issue that I am seeing is that the system is switching to grid well before I hit either 26V or 45% SOC. The system is switching to grid when at 26.6V or ~85% SOC:

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I’m not sure where to go from here to determine why it flips to the grid early. I’d like to utilize the batteries further. I realize the battery conditions of 26V and 45% aren’t equivalent, I had it set this way to see if one or the other took precedence on this setting.

Appreciate any insight/advice!

2

What I’m guessing is that the Multi takes approximately 26V when it decides to switch to grid.
The problem with LiFePo4 batteries is that you can’t really determine SoC based on output voltage.
If your batteries are connected to a GX device over CAN bus, the GX will know the real battery SoC.
The Multi itself doesn’t, since it doesn’t have the CAN link to the battery.

There are two options to fix your problem:

  • If you are not using the “Generator start” function from the GX, you could (ab)use it by connecting it to an AUX IN on the Multi and use an assistant to ignore AC In or not based on the input signal.
    The Generator start function in the GX supports multiple conditions you can use to (in the end) ignore AC In or not.
  • if you are already using the Generator start function, the backup option would be to create something in Node Red.
1 Like
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I have not used the Generator Start function. I can look into that with regards to the options presented. Thanks for the insight.