MLT PowerStar 10H and Solis PV Inverter

Hi all

I am Anton and I live in Gordon’s Bay. My only experience is in camping kits. I have a camping National Luna green Power Pack with a BN13V-108-1.4k battery, NL5 charger and a NAMIB-240 solar panel.

I am totally new to home solar.

I got my hands on a second hand MLT PowerStar 10H as well as 3 x Solis-1P4.6K-4G.

Based on what I could find in the manuals and on the internet, it looks like one can add up to 2 of these Solis (roughly the same size KW as the inverter) on the output of the PowerStar and control its output via frequency shifting.

Has anybody successfully done this?

Why I am asking as the previous owner mentioned that it did not work properly, something about communication, not sure if it was between these units or the PylonTech US3000 batteries. In the end they replaced the above with a SunSynk 8K.

I like the idea to support local manufactures for various reasons.

I am now like the dog that caught the bus but does not know what to do next.

• Should I keep the Solis or replace it with a MPPT charge controller (MLT/Microcare) as I do not understand the pro’s and con’s of the frequency shifting method.
• Local manufactured CAN bus compatible batteries like Solar MD, Blue Nova and Freedom Won seems to be supported. What about a DIY battery?
• Local manufactured solar panels it looks like only ARTsolar.

So my journey has begun.

Not an exhaustive answer, but the first thing you have to know is that the frequency shifting method doesn’t work while you are connected to the grid. You cannot move the frequency of the grid, not without your own private little Koeberg. The frequency-shifting comes into play when the grid is disconnected.

PV-inverters (like those Solises… Solii?) reduce their power when the frequency moves up. Think about an old Diesel generator, if you push energy into such an arrangement, it causes the engine RPM to go up. Push in too much and the mechanical alternator turns into a motor and it speeds up. So this is a very “old” method of doing it. From about 50.7Hz upwards the PV-inverter will reduce power delivery, and at 52.7Hz is is down to 0%. 53Hz is an emergency shutdown.

Some inverters (Victron, MLT) support frequency shifting. That means they behave like an old Diesel generator and they push the frequency up as the battery fills up. And that allows the PV-inverter to connect to the output of such an inverter.

But when the grid is there, it is locked to the ±50Hz of the grid (more like 49.8Hz some days :slight_smile: ), and the only way to prevent feeding into the grid is with the CT clamp that comes with these inverters… and then things get interesting because your PV-inverters may pull back while the inverter/charger could have been charging the battery.

Unless you are skilled enough, or you like tinkering with such thing in your free time, I would not DIY the battery. Since you like local, buy SolarMD, FreedomWon or BlueNova.

Keep the Solis? Depends. If most of your loads are daytime loads, I would keep it. It is more efficient to AC-couple the PV if it is going to be used directly.

@Stanley and @Gman are your MLT guys on this forum.

I just came back from MLT office 15min ago. Went go fetch my 10H that went in for repairs after generating 6000mw from the day it started up. So far what I know, you can run the Solis on the output of the powerstar, so the powerstar will power the Solis unit, this is following to my Gen2 unit.

But Stanley wil pop in now and give you more info. I can see him busy typing.

If you planning to sell that inverter, let me know please :wink:

Just one thing that I can add:
Depending on the age of those Solis Inverters, they may need a firmware update to work correctly with frequency shifting. The early models didn’t reduce their production at all as the frequency increased and then they would eventually just disconnect completely on a Grid over frequency fault. I can’t remember exactly when they started coming out with the working firmware by default but I do remember having to update a few of them to work properly maybe 2 years ago or so.

Depending on how old your Powerstar is, there may also be a new firmware version available for it.
I don’t think there have been any ‘critical’ fixes for a long time, but it’s always a good idea to update the firmware if you can.

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Also, if you do plan on selling one of those Solises, preferably for a really attractive price bordering on a Christmas present, I may be interested. Not because I am really looking for one, more because I can do with one in the testing fleet, and maybe make a software limiter feature for it. Of course I can also just buy a small 700W unit if I really wanted to do it… so welcome to tell me to bugger off too :slight_smile:


@Anton Please sell a unit to Plonky, he might give the community a very valuable Christmas present in return : a extra AC coupled PV inverter option for Victron users! :smiley:

What you guys don’t know is that there is a demand for off-the-beaten-path options already because of stock supply and chip-shortage issues… and I’ve already looked at a Huawei Sun2000, but had so much trouble getting that thing to even connect to Wi-Fi and open a Modbus port that I decided we’re not foisting that amount of trouble on installers and/or support personnel! Very very decent bit of kit, make no mistake, but the software side is still a little lacking. There is a sunspec thing in the making, it’s just not very mature yet.

I try to keep a keen eye on inverters that support sunspec (and as you previously pointed out implements model 123) so far I have seen 2 candidates that should be plug and play:

The Hoymiles DTU Pro S with a compatible micro inverter(s)
These Goodwe models that also appear to support model 123

Wow, thanks for all the info.
@plonkster thanks for the clarification of how frequency shifting works.
@Gman sorry, I am not planning to sell the PowerStar.
@Stanley I think the system was installed 2019/2020 so you may be right that the Solis might need a firmware update.
@plonkster, yes I might sell some of those Solises as I do not think I will be needing 3 of them. Might install 1 keep 1 spare and sell the other or sell all 3 and get a MPPT charge controller to avoid the frequency shifting issue altogether. It will depend also on the PV string layout as these Solises work in the 90-520V range with 11A, where the MLT Nomad goes up to 375V with 40A per MPPT. The Microcare MPPT is in the 20-150Voc range.
Any other MPPT charge controllers that I should consider?

I see that both the PowerStar and the Solis both have a RS485 communication port. Is this port use for reading only or would it be possible for the PowerStar to control the production of the Solis?

With the Sun2000’s I found that Modbus-RTU over the RS485 connection is the way to go unless there is a Smartlogger installed, in which case you can use Modbus-TCP to the Smartlogger quite nicely. I haven’t had any problem controlling their production either way.

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Chip shortages mean the Nomad isn’t available at the moment. It is being redesigned to use parts that are currently available but it won’t be available to buy for a while still.

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Unfortunately the Powerstar can’t control the Solis via RS485. The only control it has is via frequency shifting.

Thanks @Stanley. I assume theMLTPOWER NOMAD website is out of date then.

I would be very comfortable to put two of the Solis’s on the output. They react to frequency shifting nicely.
I would however add a Data box on the Grid power to limit these inverters while the grid is connected.
As @plonkster mentioned, frequency shift only happens during load shedding.

If you want to go the MPPT route. I would also be interested in buying one or maybe 2 of those.

Its normally used to interconnect these inverters and then connecting them to their “Export Manager” / Data box to control / prevent feedback into the grid.

@Anton sal se gaan Mppts. Ek hardloop n H10 en H8 en al my ander goed is Victron. 2 Victron mppts “250/100 en 150/100 en n spaar 250/100”, smart shunt, 2 x et112 en als is connected aan Cerbo. Als werk so ver goed. As jy hande op 2 2nd Nomads kan kry, dan kan jy dit deur die MLT Bridge hardloop na die portal toe.

Yes, looks like it.
I will mention it to them.

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@Gman dankie. Ek sal 'n bietjie soek vir 2 2nd Normads. Ek wil graag poog om so ver moontlik off-grid te gaan. Ek weet vir die winter hier in die kaap gaan dit moeilik wees. Ek het wel ook 'n 3 KVA inverter generator wat ek in so 'n geval kan gebruik as input na die PowerStar om die batterye te laai. Ek sien nie dat dit by Eskom beter gaan word in die volgende paar jaar nie. Kaapstad gaan ook met hulle beskikbaarheid van elektrisiteit koste klim en dan is dit dalk die moeite werd om af te klim en die inverter generator te gebruik wanneer dit nodig is. Ek wil so ver as moontlik alles lokaal doen en nie afhanklik te wees van die internet nie. Ek dink daar gaan 'n tyd kom wanneer die krag vir 'n lang tyd af gaan wees en ek wil nie afhanklik wees van my internet verskaffer, portal verskaffer se backup om by die portal uit te kom nie. So local is eerste, portal is 'n bonus.

@JacoDeJongh The Data box that you are talking about, it it a product from MLT or Solis?

Dis moontlik om offgrid te lewe met die grid as standby @Anton . Ek het dit so ver reg gekry en hardloop nog al die pad so van begin van die jaar af. Die City was al by my huis gewees om te kyk of hulle nuwe prepaid meter nie werk nie want hulle sien ek het Jan laas krag gekoop. Toe se ek die tegniese ou dit is so, ek het begin van die jaar laas krag gekoop. Net genoeg solar en stoor krag he. Ek hardloop tans 10kw se solar op die dak wat Noord en Oos en Wes kyk en 35kwh se stoor krag. Winter het ons maar net sekere “loads” geskywe na ander dae toe wat beter is maar verder het als goed gewerk en geen stress gehad nie. Ek sal graag nog so extra 10kwh stoor krag wil kry en se nog so 3 kw se solar, dan weet ek sit in die regte spot.

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Just an update of my journey till now.
After a lot off reading and checking out installations I decided to do it my self. So the AC part is finished. Thanks to all on this thread I have replaced my DB with a cutout surface mount DB. My old DB

New DB

Based on this thread I bought ECC SWA 16mm 4 core cable to connect the main DB to the DB in the garage.

Got my Solis AC connector based on the thread from EM.
Tested my inverter-generator (Kipor 3000) during load shedding. Had some problems with the BN52V-310-16k_NG BMS coms that would just disconnect from the Powerstar. Took the battery to Blue Nova, the tested it and replaced one of the cells and also the blue tooth module. The SOC of the BMS (123smartbms) is not accurate as it does not use a shunt to measure current. Got a quote (R7200) to replace the BMS with a new BMS developed by Blue Nova to give better SOC, but in the end decided to run the battery rather on voltage. Had to get Rubicon to come and update the firmware of the PowerStar as it did not wanted to charge the battery without the CAN cable and to see if it could solve the coms timeout issue.
Now I have UPS and the next step will be to get solar panels to connect to the Solis PV inverter.

Thanks to this site I have learned a lot.