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libor asked

Multi RS Solar 48/6000W - ongrid - confused

Hello Victron community,

I am trying to select product(s) from Victron to replace my existing Chineese Revo II 5KW unit (I started with as a kind of experiment). I am super confused though, both with the number of possible configurations and by description of device I selected.

I am on-grid, but having for two years a small solar system with 4095 Wp panels (9 x 455 Wp),two server-rack LiFePo4 batteries 4.8 KWh each and the all-in-one Revo II 5 KW. It actually performs quite well, but the SW is terrible and the output power is definitely lower than declared. I’m on 240V/50Hz grid, 1-phase solar, with no excess power returned (and the system must avoid returning any power to the grid).

So after ages of browsing I thought I found fitting Victron product - Victron Multi RS Solar 48/6000W, probably the dual solar input version (taking into account planned panel expansion). Plus Cerbo GX, which should be enough to connect to the system and manage it.

However, looking into datasheet (https://www.victronenergy.cz/upload/documents/Datasheet-Multi-RS-Solar-Dual-Tracker-EN.pdf), I am super confused by “Operating modes” chapter. No mentioning of a “Battery preference” like mode in which the system charges batteries from the solar panels and provides power to the house directly from panels and/or from batteries and if the remaining battery capacity drops bellow 20% it would switch to feeding the house from the grid.

So can this device do that? Doesn’t make any sense to me that this would be missing.

Is Multi RS Solar + Cerbo GX enough to replace all-in-one hybrid inverter/charger or am I missing something?

And how Victron’s AC2 work? Can I use it to feed my Heat Pump, which would mean it would features like: Cut off the AC2 power, if there’s too big load on AC1, or too small battery SOC, and limit to certain day time hours? I’d buy then an automatic switch, which would in a fraction of a second switch from AC2 to the grid input. Or maybe smart one, to also program availability, if this is not possible in Cerbo OS. I’m using my old inverter to feed heat pump sometimes, but have to switch it manually on and off (and handcuff my wife to prevent her to switch 5 other hungry devices on at the same time /bazinga :-)/).

I appreciate any meaningful advices!



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4 Answers
Alexandra avatar image
Alexandra answered ·

@Libor

You can do all that without the cerbo.

The internal programming over Bluetooth allows you to set up the inverter for that

If you download victron connect there is a demo library, you can play around in the settings there to get a feel for what is possible.

AC2 is not programmable on the Multi RS. With grid it is on, no grid = off. If you need that then use a Multiplus.

I have my water heater on AC1 but have a node red flow to control when it switches on. So for fine control like that, you will need the Cerbo. So there us a still an option for load control that way.

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libor avatar image libor commented ·

Those are helpful remarks, thank you.

OK, I can start without Cerbo and in case of any limitations, in the worst case scenario, I'll purchase one. I'll assume that the "GX" and BT module it has, can handle basic status reporting and configuration. I thought I need Cerbo, because the schema of basic system in the datasheet shows it connected to Cerbo unit.

So AC2 is the same output (i.e. power from battery), which is conditional to grid availability. If I understand it correctly and there are no other limitations (?), it may still make sense to put Heat Pump on AC2, as the grid-off state is extremely rare here and in that case the direct bypass wouldn't work either. My only problem is, that I couldn't find so far a smart switch (for DIN rail) that switches between two 1-phase inputs, while I can easily buy a switch that switches automatically to 2nd input (within like 0.01s) when first input turns off.

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Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @Libor

Indeed, as Alexandra said above, the Multi RS can do that.

Also, don't worry about power hungry devices. Throw them all at the Multi RS because, as you can see from the Multi RS brochure, it has a 50A passthrough / transfer current, which means over 11kVA of power that can pass through it and if the battery is unavailable (low SoC), or the consumption is over its internal inverter power (6kVA), it will "borrow" the difference from the grid.

Alex

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libor avatar image libor commented ·
Oh that sounds great. My old invertor should have done the same, but when I got a warranty replacement, the new one just switched to grid input. Things like that got me annoyed and that's why I want to upgrade to Victron.


I think I could put it on AC1 if you suggest, if AC2 turns out to be a bad option. I have a return line to the main fuse box that probably wouldn't sustain 11kW for prolonged time, but the Heat Pump line is split right underneath the box, so full power wouldn't go through that return line. Will have to check that setup with my electrician, also if the line between the split box and inverter needs to be larger.

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Alex Pescaru avatar image Alex Pescaru libor commented ·


AC2 is directly connected / hardwired to AC input.

Also get the Multi RS manual and study its way of functioning and modes of operations.

https://www.victronenergy.com/upload/documents/Multi_RS_Solar/62787-Multi_RS_Solar-pdf-en.pdf

You must familiarize a little with Victron way of thinking, as it's different than Chinese SUB, SBU and USB modes... :-))


ac2.jpg


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andrii-podanenko avatar image
andrii-podanenko answered ·

I switched from Chinese voltronic to Victron Multi RS 6000 Dual Tracker almost a year ago.

It can do everything you need, as well as it has advanced AC in control options in order to connect/disconnect by certain rules.

Latest firmware also has improved Solar Shading control.

If you need monitoring - worth adding Cerbo GX to the system

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Alex Pescaru avatar image
Alex Pescaru answered ·

Hi @Libor

Hope that your confusion has cleared a little.

Just to add some more thoughts if you need them... Some of them were already stated, but in the "search anxiety state" they may slip between the cracks... :-))

Be aware that the Multi RS, with its current firmware, its not exporting to the grid. And even if the future firmware will be able to do export, for sure it will be an option in config to not export.

If you want remote control over internet or if you need that a battery BMS to communicate with the Multi RS, then you should get a Cerbo GX at least (low performance, 2 core, but enough for the above). If not, an Ekrano GX (higher perfomance, 4 core) it will be better.

Solar will always be used with priority, so the old USB mode is not so easy to obtain and to be honest, in my opinion, doesn't matter.

So remains only SUB, equivalent with the setting mode ESS - Keep Batteries charged and SBU, equivalent with the setting mode ESS - Optimised with/without Batterylife. If you need BatteryLife or not, it depends on preference.

Over-paneling on a MPPT (4kWp on a 3kWp tracker) it's not necessary a problem as long as you respect the maximum input voltage of the tracker (and not forget here the panel's voltage correction with temperature) and the maximum short circuit current of that tracker. Better to be safe than sorry.

Also see that there is a limitation on Victron's HV MPPTs, which says that the maximum string voltage must not be bigger that battery float voltage x 8. Eg. battery float voltage 54V, then no more than 54x8 = 432V (again, corrected with temperature) on that tracker.

Take into consideration that the 5KW inverted real power is about the maximum possible with the Multi RS and this is the power you need to consider when you will be only on battery at some point along the time axis, without grid.

Hope this helps...

Alex

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libor avatar image libor commented ·
Thank you so much @Alex! About every row you wrote is very valuable information for me. Even when I knew some facts, I wasn't always sure I'm interpreting them right.

I've started to give up on Multi RS due to lack of specific information. And got insecure if it's a correct choice and as a culmination of nearly 3 weeks of research in total I posted my 2nd post, but it got closed as broad.

I'll have to think about the 9 panels as you've mentioned it and learn about varying voltage, since the simple calculation 48 V * 9 = 432 V is just on the edge (52 V * 8 = 432 V you've mentioned). I remember the manual sets also amperage limit 13 A, I get roughly 9.5 A (455 W / 48 V). That confused me, since it also says max 3 kWp solar string. But I can easily disconnect 1 panel for now if it doesn't pass (I plan house extension where the panels will be relocated). Unfortunately running 2nd pair of cables now is relatively unfeasible, since the protection tube has like 6 tight turns (can't push more cables through) and it would be a major construction hassle to add/replace cables.

I didn't know Cerbo GX is 2-core, but asume it's OK for running a little linux server. I'm familiar with Raspberies and could run it on i.e. Rpi 4B with 4 cores as (I've read) some people do, but I fear it could become a time sinkhole for a little advantage.

So Multi RS solar + Cerbo GX (Ekrano) + 8 (9) panels + my 2 server rack batteries sounds like a meaningful setup.

Once again, many thanks!


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