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wdavid asked

Multiplus II - ESS mode 3 drops Inverter from bulk to passthrough every 3 mins for 5 sec

Hello,

I have a Multiplus II 3000 connected to a 48V LiFePo4 Bank, the system is running as grid connect ESS in Mode 3 (external control), I set the power-setpoint via MQTT and it works as expected.
When inverting the Multiplus is always in Bulk mode and responds to the given setpoint as expected. Every 2-3 mins the Multiplus stops producing power, goes into passthrough for 2-5 seconds and switches back to bulk afterwards. (See attached graphs)

The graphs are generated with the values published via MQTT by my external controller and the venus os. victron-drops-graph.jpg

This happens in all load situation (e.g. when continously running around 100W or 2000W), at all SOCs, the battery voltage also is constant. The multiplus does not report any errors.
I've tried different venus OS Versions, no BMS connected to VenusOS and with BMS connected to VenusOS, same behaviour.

When setting a positive power setpoint for AC charging no 'drops' occur, it only happens while discharging/inverting.

Can someone explain this behaviour? I'm wondering if there might be a fault on my side or why the inverter is behaving like this. Can i provide more data to help troubleshoot this?


Many Thanks,

David


Multiplus-IIESS
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1 Answer
Paul B avatar image
Paul B answered ·

There a few things that can affect this BUT I dont think you have anything to worry about its doing what it needs to do.

IE the BMS maybe saying charge the battery then saying stop charging ie reduce charge amps to zero then the batteries drop in voltage a bit and the bms says charge again.

look under device settings and then your bms and then right at the bottom the parameters

another thing is that the batteries internal BMS is turning off then back on, Ie the cells are balancing this may stop happening in a few days or weeks as the battery cells balance.

check your batteries internal BMS





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wdavid avatar image wdavid commented ·

Hi Paul,


thanks a lot for you answer! Unfortunately it took me quite some time as to answer as I was not onsite for a longer time.

I've conducted several experiments, but with everything I've tried I could not get the Inverter to not drop the power every few minutes.

I've diconnected the BMS from Venus OS, I've disabled battery monitoring for the Multiplus, I've switched of the 'has DC System' setting, I've checked the Input voltage and current using an OSZI. There is no change. Even when removing the BMS completely to rule out everything BMW related (directly connecting the Multiplus to the Battery bank without any switches in between) the multi keeps dropping power.

Is there any place where I can get debug logs or something related from the multi why it behaves like it does? We would really need it to just behave like an 'dump' inverter following it's given setpoint. Am I the only one who has this behaviour in ESS mode 3?


The behaviour is pretty annoying for the building inhabitants here, when under load the Multi creates a humming noice which is silent but perceptible in the house. While the multi drops it's power the noise is gone as well. This change of sound makes the sound really present and perceptible. If the multi would just continuously run and continously humm it would not be annoying at all.

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