3 Multiplus in parallel + GRID + PV + ESS do not work

DIY
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1

Good morning everyone,

Today marks exactly one month since my first attempt at setting up the system, and I’m declaring it a complete failure.

I bought 3 Multiplus 48/5000, P/N PMP482505010, all from the same series HQ2250xxxxxx.

My non-working setup is: GRID + SOLAREDGE → AC IN → 3 Parallel Multiplus + ESS + 30kWh Pytes batteries. See the image below for the full setup.

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Here’s the reality:

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Over the past year, I’ve read everything available on Victron’s site, watched all the pro videos, and gone through every group (Facebook and this one) trying to find a solution.

The AC cables (in and out) are all 6 meters long with a diameter of 10mm². The battery DC cables are 70mm² and 2 meters long, with an additional 2 meters of 4/0 AWG cable to the batteries.

Initially, I used just one Multiplus, and everything worked perfectly. Here were my settings:
(I cannot add more that 5 images)…

The problems started when I connected all three together.

I spent weeks trying to figure out why every time I plugged AC IN into the 3 parallel Multipluses, they made these strange noises (woom…woom), typical of frequency issues. The Solaredge would shut down, and sometimes even the main breaker tripped.

After countless attempts, I found the issue: it was the LOM. Once I disabled LOM, all three started working correctly. The documentation was vague here, talking about interference issues but never mentioning parallel setups with Grid Tie.

Anyway, it worked, but not perfectly.

When I was running just one Multiplus, the power drawn from or fed back into the grid was always around 0 (with the usual small spikes of ±50-100W). But with two Multipluses, ESS can’t hold the grid at 0 anymore. It starts drawing around 250W from the grid, fluctuating by ±100W consistently.

When I add the third one, the grid draw jumps to an average of 400-450W with a variation of ±200W!

I’ve tried endless settings and combinations. There’s no way to fix this behavior.

In this image, you can see (from my monitoring software) how the green grid line is stable around 0.

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Here’s what it looks like with 2 Multipluses in parallel (you can see it jumping off zero):

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And here with 3 Multipluses:

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You can see the green grid line way higher (around 450W) and only dropping when AC IN draw decreases (because the house consumes more).

Can anyone help me before I sell everything and buy a 15000?

Thanks in advance.
glfp

2

@glfp
Sell and buy the 15kVa. Parrallel set up is notorious for hair pulling. One of the reasons why it as a diy set up is not officially supported (noted in the documents).

If you are not ready to give up yet, start with no AC PV.
Run loads (inverting) check your load balance between units. If its not within 5% fix it there first.
Possibly by switching to lower gauge AC wire. In the manual note it says to use longer thinner gauge. Resistance is the key to balance.

3

Thanks, Alexandra.

I’ve already tried using 6mm² cables for AC IN (no issues on AC OUT or inverting mode), but I had the same problems. The cables are 6 meters long, so I don’t think the size is a major factor.

The main issue really seems to be with ESS when running 2+ units in parallel… with just one, everything works perfectly!

It feels like there’s a lack of coordination between the Multis.

Another thing: I also tried installing ESS only on the master unit instead of on all the Multis, but it behaves the same way.

4

Dont know what your country regulations are, but 10mm2 is way to thick, as alexandra suggested lower it, maybe as low as 4mm2 ( if thats according local regulations)

Also i would suggest to contact your local victron dealer, parallel systems can be really to complicated to get running (diy)

5

Yes but how is the load share? You can even test the system with no ESS. Just a DC amp test on the battery cables will give an idea.
( hence the inverting suggestion). Ess has no effect when inverting.
Your test where you removed LOM infers that the input side also has different resistance.

6

Check this, maybe you have 1 or 2 affected units:

https://community.victronenergy.com/uploads/short-url/1yGMSZUMRc0yyHJiYgkQ5rkwZPm.pdf

7

Hi @dognose

unfortunately (or “fortunately”) I do not have the jack for Current Energy.
I have this kind of connector

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Do I need to leave or remove ?
I just remove both connector from my two parallel Multis and now it put constantly 100w INTO the grid, while before it consume FROM grid.

To leave or to remove ?

Thanks

8

If you don’t have the jacks, then there shouldn’t be an issue with that.
Most likely Victron replaced that connector for this reasons.

In that case, I would put it back in place, as shipped originally. empty Plugs with a bridge are usually there for a reason (over leaving it just empty)

Thought you have 3 units?

Do you run one independent, or just currently disconnected for testing purpose?

9

Yes 3, but at the moment I’m running with only 2 because with 3 is more and more instable.

BTW, I just reput the plugs in their normal position because Cerbo shows

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instead this normal behaviour

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NOTE: I have 0 load on ACOUT1 :slight_smile:

11

@lxonline as far you know, LOM must be enabled only on master or in all the units ?

12

You have a 3-phase grid, so why you want to setup a single phase ESS?

13

Yes, I only use a single phase of the three. Current Solaredge is also monophase.

14

All settings are the same on all the units.
The master - following assignment obviously is different and the ESS assistant. The master controls the ESS - but the assistant still is installed on all units.
Did you update all firmware gx inverters etc?
Are the grid meters assigned to the correct position in software in the system?
Also if there is no load on the AC out then switch it off in settings.
And yes as M_Lange mentioned 3 phase is way easier to get right.

15

But why???

I’m sure you have less trouble with a 3-phase system.

16

For sure, but Victron in Italy is not certified with CEI-021, so I cannot configure in that way for an on-grid/grid-tie.

I must configure the Victron with zero grid feed, but in that case 4kw on every phase is not sufficient for me.

17

A further thought if the inverters are seeing a load and there is no load then they are feeding into each other. So still maybe a load sharing resistance issue.

18

Do you mean that loads ?

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I supposed it was the autoconsumption of every Multi … why they should feeding each other ?

Do you note some strange connections in my schema ?

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All in monophase, using only one phase from the grid (the other two are completely disconnected)

Thanks

19

Usually system consumption is seen in AC loads. They can see each other as load if the wiring is not balanced.

20

@lxonline

When considering a Victron Multiplus 2 15000 versus a 5000 model (assuming a single unitconfiguration), are there any specific factors to consider beyond the obvious differences in power output, cable sizing, and related power considerations?

Additionally, are the configuration processes and management interfaces essentially identical between the 5000 and 15000 models, or are there significant differences in how they are set up and controlled?

As I understand there are no difference, but just in case … :slight_smile:

Many thanks

21

@glfp
In programming no. Set up it has the same features. (Except the 15s can’t be parallel connected at this point :upside_down_face: to my knowledge)

It will be more efficient than 3 x5kVa parrallel. Way less wiring in AC and DC way less switchgear and way less complicated to install.