markus avatar image
markus Posted ·

All in One 3-phase ESS system cabinet

Hello Community,

How compact can a 9000VA 3-phase ESS system, including 10kW/h batteries be?

I tried to find this out :o)




5.1kWP of solar (15pcs. 340WP mono) panels will feed the Fronius (3kWP,9s,1p) and the Smart Solar MPPT (2kWP, 3s,2p)


Four big 230V AC powered fans are mounted on the top, to do ventilation and to get the heat out, they are not even very noisy.


I am still waiting for the battery pole covers and a 19-inch rackmount 8-way Schuko distributor socket, to arrive. The distributor should cover the wooden plate underneath the batteries


Excess PV power can be used, to heat water by 48V DC water heating elements. The 48V-100A Battery Protect is there, to switch the water heating elements on and off, so no danger of melting relay contacts exists. The BP is controlled by the BMV relay and the Smart Solar MPPT relay. I have no best practice ready yet in winter. However, first tests proof, that I have a good solution.




Stk. Description SKU

3 Stk. MultiPlus-II 48/3000/35-32 PMP482305010

1 Stk. SmartSolar MPPT 150/45-Tr SCC115045210

1 Stk. Cerbo GX BPP900450100

1 Stk. GX Touch 50 BPP900455050

1 Stk. Energy meter EM24 - 3 phase –

max. 64A/phase REL200100000

1 Stk. RS485 to USB interface cable 5m ASS030572050

2 Stk. VE.Direct Cable 3m ASS030530230

2 Stk. LiFePO4 Battery

25,6V/200Ah smart BAT524120410

1 Stk. M8 Circular Cable Male to Female

3 pole 1 m (Pack of 2) ASS030560100

1 Stk. VE.Bus BMS BMS300200000

1 Stk. Orion-Tr 48/12-9A (110W) ORI481210110

1 Stk. Smart BatteryProtect 48V-100A BPR110048000

1 Stk. Battery Monitor BMV-712 Smart BAM030712000

2 Stk. RJ45 UTP Cable 3m (VE.Bus) ASS030064980

2 Stk. RJ45 UTP Cable 0,9m (VE.Bus) ASS030064920

1 Stk. Fuse holder for MEGA-fuse CIP000100001

2 Stk. Busbar to connect 6 (1500 A) CIP100400070

5 Stk. Modular fuse holder for Mega-fuse CIP100200100

5 Stk. MEGA-fuse 125A CIP137125010

1 Stk. MEGA-fuse 500A CIP136500010

RGB LED strips on the top, light the cabinet’s internals.

A Wi-Fi capable RGB LED controller powers the strips. It is possible to change colors on SOC, active warnings and alarms, etc. via Node-RED.

To make this happen, install the node-red-contrib-magichome node.

Information, how to get Node-RED running on a GX device can be found here: Venus OS Large image: Signal K and Node-RED [Victron Energy]

This is how the LED’s are controlled in Node-RED:


I want to create a more practical control logic for the excess PV water heater too, but for that I need better sunshine to do tests.

If there are questions about details, I am happy to answer them.

Best Regards,


Multiplus-IIESSmppt smart solarLithium battery Smartfronius and victron
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Outstanding Markus, that really looks good.
Thank you for sharing.

Was this setup tested for heat distribution inside this rack cabinet?

I can see problem for Fronius and this Multiplus-II above it.

See this.


Fronius will be nicely cooking this MP-II from the bottom.

But it may be good setup for cold locations.

These thermal pictures are useless without the temperature scale.

marekp avatar image marekp Matthias Lange - DE ·

I would understand comment like yours from someone having zero experience in PV.

But you!

Are you suggesting that this orange represents negative temperatures?

The heat leaving this Fronius is totally blocked.

Maybe raising this Fronius away from the back wall would improve the heat distribution.

I do not think those four fans will be able to evacuate close to 2kW of heat energy generated inside this box.

This is why I asked my question about heat distribution inside.

Orange/yellow/white can be just 5° warmer or 50°, depending on the sensitivity and the scale.

(but to be honest I don't have much experience with Fronius.)

marekp avatar image marekp Matthias Lange - DE ·

@Matthias Lange - DE

I have an inverter that gets up to 80C at summer days.

It is not Fronius but Fronius is up there as well.

It can get to 70C on the top air outlet.

The heat leaving this Fronius is totally blocked.“

No it‘s not. The space looks smaller than it actually is.

I do not think those four fans will be able to evacuate close to 2kW of heat energy generated inside this box.“

2kW is a bit high estimated. The datasheet says, fan module airflow is 9.2m3 per minute. This is a lot.
For now, I can’t get the cabinet even warm :o)


You right, 2kW is on the high side but 1.5kW is possible.

You cannot relay on the efficiency quoted in the catalogs.

I measured my MP-II, and it has 88% (real life) DC-AC efficency, when spec says max 95%.

My inverter has 93% when spec says 97.5%

If you rely on those fans for keeping this cabinet cool, you should install some rotation sensors to make sure that they are turning when needed.

Now, in winter, my inverter is not even getting to 10C :)

What will happen in the summer is different story.

Hi Marek,

Now, in winter time it cannot really be tested to the maximum but my thoughts on this:

The 3kW is the smallest Symo unit available and therefore the least heat producing Symo.

The cabinet will be located in the basement. (max. 19 degree celsius in summer.)

If necessary, I can construct a piece of metal guiding the airstream in front or behind the multi instead of straight up.

There is space behind the units, you cant see that in the picture.

The Fronius is mounted on rack trails, so I could very easily move the fronius down to have more space to the Multi, but this won’t look good...

I can open the door for maximum ventilation in summer



Do not take my comments wrong, I like the cleanness of it.

My only "but" is about heat dissipation. It is my "professional bias". For many years I was designing industrial enclosures and sometimes heat was coming from least expected places.

Placing this cabinet in the basement could be OK for the temperature reasons but what about humidity?

I was considering placing my LFP batteries in the basement for the temp. reasons but with over 80% humidity there I decided to place them above the ground. I would newer place electronics in such humid environment.

Here on this forum I once asked a question about the distances required around MP-II and the answer from Guy surprised me.

On the other hand following the installation guides is important for eventual warranty claims.

Here are the Fronius mounting requirements:


fronius.png (115.4 KiB)

No, the reason I posted this, was to discuss things. I appreciate your input.

My basement is not very humid, so this should be no problem.

I have read the mounting instructions. There is enough space behind the Multi, maybe I have to do light modifications, so that the hot airflow in summertime will take the route behind and is not sucked in by the Multi above. I could cut out additional ventilation holes in the backdoors, or even remove one or both of the two back half doors completely. We will see if that is necessary in mid-summer. For now, everything is cool ;o)

Those extra baffles deflecting hot air from below is a good idea, but I would ad also baffle to direct cold air to the intake of that central MP-II. Fronius will be hot as a hole, not just air coming from his upper air outlet.

I had the same problem with my PV inverter. Some "not quite smart designer" of it placed 3 (1 for each phase) inverter heat sinks one above the other. The top one was always overheating in the summer time.

I modified the air travel at the back by adding baffles directing air from heat sinks to the left side and bringing cold air from the right side.

Next summer inverter stopped overheating. :)

What is that hot spot in the low left corner of your Fronius?


What size (power rating) is your unit?

1609316178980.png (79.5 KiB)


To be correct, I do not have a Fronius inverter. Those pictures are from Internet.

I do not now exactly what is that hot spot, but in this area is a DC switch at the bottom.

It could also be connection of the PV DC wires.

Yes, that will be the DC switch. It looks like mine is located more towards the back of the unit.
The vertical line is strange. DC wires should go on the right side of that.

It seems like, the unit was producing full power on that picture, so it would be interesting if it was a 3kW or 20kW unit. And the temperature of the unit and the airstream would have been interesting.

My neighbor has a thermal camera. When there is good sun again, I am going to take some pictures


The pictures are from this site. You can find there some info about the actual temperatures.

Thank you Marek.

PS.: the cabinet can be opened from the back and the sidewalls come out easily. I am sure temperature will not be a problem. I will update this in mid summer though :o)

I know this cabinet. I have identical and plan to use it for battery bank.

If someone is interested, it's this cabinet:

DIGITUS Netzwerkschrank 36HE Unique Serie - 800x800 mm (BxT)

Link: DIGITUS: DIGITUS - Produkte

Wow! That's a very nice and clean installation!

Danke Matthias.


Can you explain why you placed the 3 MP-II inverters above the Fronius?

If they were below Fronius than they would be closer to the battery and the DC wires would be shorter

Yes, I have made this decision because of the mounting possibility. The side Multis are hooked on the structural support of the cabinet. It was just ideal. The line breakers and RCDs and the main battery fuse are better to reach there

But it is for sure a good option to do it the other way round. Maybe next time :o)

The missing parts arrived: distributor socket and pole covers.


distcover.jpg (555.3 KiB)

Hi Markus,

indeed, a very nice setup! I have not thought about such approach ;-( I simply assembled the components to a concrete wall.

Interestingly I have a quite similar setup (Fronius on AC-out and MPPT on DC side), where I also plan to use excess power for power to heat (in combination with a myPV device).

Especially with the Fronius on AC-OUT1 however I realized that in a zero-feed-in configuration, it gets throttled in such way that power is not transferred to the DC-level (in my case to load batteries).
In your case you might not have the Fronius excess power available neither for PTH nor for loading your batteries.

Therefore I would be highly interested, if you experience also these issues that I have in my setup:


Hi Thomas,

Thanks, I have followed your posts with interest.

At the moment, I have not installed all of the solar panels yet and the ones that are connected, are covered in snow. But I will test that when I can and come back to you.

Best Regards,




Markus contributed to this article

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