robertc avatar image
robertc asked

Multiplus 2 occasional grid charge while it should run on battery

I noticed a weird behaviour in my 3 phase system - 3x Multiplus, 6x Pylontech US3000C, Cerbo. with hybrid setup with grid connection - grid feed in is turned off with grid feed target 0. It's very obvious during night time, where there very little load.

What happens is that few times within an hour, there's occasinal charge going to battery from the grid. It's not much, couple hundreds of W there and there. Battery at that time was around 65%. I log data from TCP Modbus every 5s to my app where I have some charts, I double checked CSV file from VRM portal.

I put screenshots into a single file. Charts are from one hour logging during night. From top: Battery Power (W), L1, L2, L3., down at the bottom are values from VRM CSV file, you can see the load is quite low and constant, but the system works on battery and then from time to time it just acts weird.

Can someone please explain that or give me suggestings how to prevent this?


Multiplus-IIgridess discharging
multiplus.jpg (1.2 MiB)
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nickdb avatar image nickdb ♦ commented ·
Does the VEbus state ever change at the same moment?
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2 Answers
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matt1309 answered ·

Hi @RobertC

What are you using to monitor grid input/output. If it's a meter I've noticed that there's often a slight lag when compared to CT clamp or internal multiplus sensor.

ie for my system if 1000w of load turns on, the multiplus takes a few seconds to ramp up to 1000w to cover the load and the grid covers the difference in the meantime. I've noticed the time lag is worse on my setup using ET112 energy meter compared to CT clamp.

If this is also happening for you I imagine the spikes of grid usage are where a load is turning on during the night, maybe a fridge compressor or something similar that draws for a short period of time.

My setup is all wired in parallel with the grid (on ACIN), I'm not sure if moving loads to AC OUT side helps with this, not sure if someone else can confirm that. However I have heard folks have greater success using CT clamps/internal clamps rather than external meters.

I've also heard some of the new meters are faster however not sure if they're supported yet (i recall spotting that in one of the v3.0 Venus os Beta release notes)

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robertc avatar image
robertc answered ·

Hi, I don't have external meter, measurements come from the Multiplus inverters. I know that sometimes i takes a second to balance the load for the grid to stay around 0, but that's not the case. It's happening on all inverters, but only one of them has a fridge on. I don't think it's associated with the load to be honest because you can clearly see that all inverters are sort of synced when experiencing this behaviour. Also when there would be a load or unload spike, I don't think the inverted should be able to put amps back to the battery right? It should maybe overflow to grid or feed from grid, but not actualy change status to charge.

Does anyone know what is the most newest Multiplus II 3000VA FW version? Mine are currently at 487. I don't have admin access to VRM for my install as it was done by the company. Maybe I could ask them to run the remote update for those inverters and see if that helps.

I also noticed that during these issues there's a weird growling noise coming from the inverters that comes and goes in waves of few seconds and when things settle and inverters finally realize that they should just keep inverting instead of changing to charge and discharge, then it goes away, just saying :)

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matt1309 avatar image matt1309 commented ·
No worries, that was my best guess. Does sound odd.
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Related Resources

MultiPlus-II Product page 

MultiPlus-II Manual

MultiPlus-II 230V Datasheet 

VE.Bus Error codes

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