I am having difficulty running two multiplus-ii 5000 in parallel. Located in Europe i have a 3-phase incoming connection, but for parallel connection using 1-phase off-course.
They do function alright in parallel and system is stable if i do run them from DC (solar mppts and batteries) but as soon i apply incoming AC there is some issues and so far i have 2 different scenarios:
Both multis are connected on the same phase AC-in with common ground and earth.
AC-out-1 and ac-out-2 are also paralleled between multis with common ground and earth.
Both multis connected to the same battery bank.
All DC and even AC-in and ac-out cables are same dimensions and lengths.
Scenario #1. Both multis connected (and set up) in parallel without any assistants installed:
When AC-in is switched on (after a 60s delay) they start to hum quite loud in wave pattern - louder-quieter. Meanwhile the loads on AC-out are being supplied.
I cant accept that as normal, therefore i do not connect them to AC-in at the moment.
Scenario #2. Same connection but now with ESS assistants installed on both multis:
When AC-in is switched on (after a 60s delay) a very rapid LOUDER than without ESS humming takes place that is VERY short and results in disconnect with the slave unit displaying the overload red led for a sec. Loads eventually being dropped as well.
This happens WITH or WITHOUT connected loads on AC-out.
That is a scary event so i am not repeating it.
Meanwhile CERBO does not give any other error except "grid lost" so no clues there.
I did test both units standalone, with ac-in and ess installed. works as expected.
I did test and replace data cables between multis and cerbo. also tried to place them in different routes. no change.
I suspect one of the multis is defective as it is different from the other - it is louder in normal operation and it has "more noises" inside of it. Also it does not follow the AC-2 out relay assistant setting and start switching on-off the relay at 90% SOC while it is set to turn on only when SOC is 95% higher and turn off below 92%. same setting on both multis. and the internal battery monitor is not enabled.
i see there has been a very similar issue: https://community.victronenergy.com/questions/130676/parallel-multiplus-in-ess.html
unfortunately data cable replacement and relocation did not change a thing.
I understand there is a possibility to connect them multis in parallel-standalone connection when one of them is connected to cerbo through MK3. but that is not a solution to solve the current issue as i expect to be able to use all advertised applications.
please help me to solve this mysterious issue.
I have spoken to my local distributor but their knowledge/experience is not sufficient to solve this.