Hybrid Inverters - Split load between PV+GRID

[EliteSolar]

Hi Guys,

So I have been thinking to build a new setup without batteries. I need a hybrid inverter , If I am asking 1100watt load and the solar panel only provide 1000watt , then the grid will supply 100watt more to meet the 1100w load demand. I'm thinking around 5kw output inverter.

SHORT READ : I want an AIO hybrid inverter that can split the load between the grid and my PV panels, I look at the EASUN models , like REVO II , SV II and SV IV. I want to pay max 800euro. What are the differences between those models ? SV II and SV IV look about the same just led lights and wifi and 500w more inverter output power ? Do people know if there are any other differences ? Which other models can do that ? Some people where complaining the REVO II is not very good and not true 5kw inverter and has some problems... what about SV II and SV IV ? Or other models ? It's not very clear which models can do that...

Is there an ideal voltage range when wanting to convert PV DC to AC directly ? Some people say over 200V , some say ideally 350V ? Some say 450? Or is it very model specific ?

EXTRA INFO : I live in Greece and I get lots of sun especially the whole summer doesnt have any clouds for 6 months and I basically want to use the power directly from the solar panels . For me batteries don't make any sense at the moment because I have to pay 580euros for 24V 50AH Lifepo4 , just to be able to save 1.2kwhr per day ? Not a lot. A quick math says that a 1.2kwhr battery holds 30cents worth of energy per day or 110~euro worth of energy per year ( not a lot ) so basically "kinda" means 5 years just to pay off the battery , id rather put a couple more solar panels ? Also its supposed to be better to convert PV DC to AC directly , better efficiency.. Am I missing something? That's why I want to build a batteryless system ( I have access to cheap night grid power ) .

Many thanks
ES

 

[Put power to the ground]

I know the new Growatt 3000 and 5000 will run battery less as you describe. Ive had my Growatt 3000 for only a few days and it's working well at least in the aspect you describe (it has switched to 50hz from 60hz without cause twice on me and Im trying to iron that out, Im in the US. Other than that it's done well). I ran it for a day battery less and then quickly decided you're best with even a small battery. With a 600wh battery I can keep my fridge and water cooler running without any grid power even on cloudy days during daylight hours. You're just leaving a ton of power on the table unless your loads are on all the time. My loads only run about half the time during the day so the rest of the time I would be losing out on power.
For reference, my fridge pulls about 400 watts running and water cooler can get up to 550 watts I assume when the heating element is on (it has hot water also). I can easily get into 900-1000w with both running but also only down to 5 watts when neither is running. I have 12 250w panels hooked up to it and have so far peaked at 2250w solar output. So on sunny days during peak Im leaving half my power on the table without a battery. You quickly see how you could easily be running into the night with even a small battery...
I would recommend looking for alternative batteries. My battery is from a honda civic hybrid and it's NiMH which is very inefficient (takes 150% power input to charge Ive read). I only paid $30 for it though and otherwise every time a cloud comes or load surges I would be pulling from the grid.

 

[mrzed001]

The EASun inverters are the clones of the MPP Solar/Voltronic Axpert inverters.
If you can, buy the original. You get better support, better warranty.
And better product, like in many EASun inverters the PE-N relay is missing !!!

The MKX 5kW inverter is an Online UPS (double conversion)
The MGX 5kW, MAX 8kW, MAX II 11kW inverters do bypass and produce into the line in the same time.
So load is 3kW and you have 2kW from PV then you will use 1kW from Grid.

They all have 450-500Voc MPPT-s. So you need at least 6-7 solar panels connected serial for them.
The ideal is 9s, so 9 solar panels serial ... or 9s2p (9 serial and 2 parallel from that)

 

[RCinFLA]

For sinewave PWM conversion you need DC voltage to stay greater than peak of sinewave plus any IR voltage drop losses in switching devices and PWM filtering.

For 240vac, the minimum is about 350vdc. 240vac AIO typically run their HV DC bus between 380 vdc and 500 vdc. The HV DC filter capacitors will slump in voltage a bit during peak load currents of AC sinewave peak. HV DC bus electrolytic capacitors typically have a 500 vdc maximum rating.

For 120vac AIO, the minimum is about 200 vdc. 120vac AIO typically run their HV DC bus between 220 vdc and 300 vdc. HV DC bus electrolytic capacitors typically have a 315 vdc maximum rating.

The low-cost HF AIO's run their PV SCC as a boost only converter so the PV input voltage cannot exceed the inverter HV DC bus. There are some that have an additional forward converter stage between PV SCC HV DC output and inverter HV DC bus (typically 500vdc to 250vdc conversion). This adds a couple of percent additional power loss due to the extra intermediate converter, but it allows SCC to run PV input array at higher DC voltage than inverter HV DC bus and provides galvanic isolation between PWM sinewave AC chopper and PV input terminals that is not provided on low-cost HF inverters. On low-cost HF inverters the two PV pos and neg terminals are riding on top of the polarity chopping inverter HV DC bus which is why you must use double pole DC PV breakers to break both the PV pos and neg lines.

This intermediate PV path converter is a necessity for U.S. 240/120vac split phase HF inverters which are two series connected 120vac inverters with two independent HV DC buses. The intermediate converter allows the PV power to be shared to both independent HV DC buses and provides isolation between the two internal HV DC buses and PV input terminals.

The PV SCC boost converter has better efficiency when PV array voltage is nearer the inverter internal HV DC bus voltage, but since Vmp is typically 0.81 to 0.85 of Voc and you cannot let Voc of PV array to get above inverter HV DC bus, the closest you can run PV Vmp is about 85% of inverter HV DC bus.

 

[EliteSolar]

I know the new Growatt 3000 and 5000 will run battery less as you describe. Ive had my Growatt 3000 for only a few days and it's working well at least in the aspect you describe (it has switched to 50hz from 60hz without cause twice on me and Im trying to iron that out, Im in the US. Other than that it's done well). I ran it for a day battery less and then quickly decided you're best with even a small battery. With a 600wh battery I can keep my fridge and water cooler running without any grid power even on cloudy days during daylight hours. You're just leaving a ton of power on the table unless your loads are on all the time. My loads only run about half the time during the day so the rest of the time I would be losing out on power.
For reference, my fridge pulls about 400 watts running and water cooler can get up to 550 watts I assume when the heating element is on (it has hot water also). I can easily get into 900-1000w with both running but also only down to 5 watts when neither is running. I have 12 250w panels hooked up to it and have so far peaked at 2250w solar output. So on sunny days during peak Im leaving half my power on the table without a battery. You quickly see how you could easily be running into the night with even a small battery...
I would recommend looking for alternative batteries. My battery is from a honda civic hybrid and it's NiMH which is very inefficient (takes 150% power input to charge Ive read). I only paid $30 for it though and otherwise every time a cloud comes or load surges I would be pulling from the grid.

Hi,

That's why I am buying an inverter that can share/split load. I have access to grid. So when my air con asks 1.1kw and my PV provides 1kw , it will draw 0.1kw , so I will never waste any power,given I have some loads during sunshine . I don't want batteries.

But thanks for your input.

The EASun inverters are the clones of the MPP Solar/Voltronic Axpert inverters.
If you can, buy the original. You get better support, better warranty.
And better product, like in many EASun inverters the PE-N relay is missing !!!

The MKX 5kW inverter is an Online UPS (double conversion)
The MGX 5kW, MAX 8kW, MAX II 11kW inverters do bypass and produce into the line in the same time.
So load is 3kW and you have 2kW from PV then you will use 1kW from Grid.

They all have 450-500Voc MPPT-s. So you need at least 6-7 solar panels connected serial for them.
The ideal is 9s, so 9 solar panels serial ... or 9s2p (9 serial and 2 parallel from that)

View attachment 107466

Hi,

What exactly does "PE-N relay is missing !!!" mean ? I know what a relay does but not what a PE-N relay is.

Can you show me proof that EASun are missing these relays while the same model from MPP does have it ? All the ones we opened , similar models , where the exact same inside, definitely made in the same factory.

I have read the story about EASun/Voltronic/Sorotec etc , I know the MPP range is 120-400V on most of these inverters.

Thanks!

For sinewave PWM conversion you need DC voltage to stay greater than peak of sinewave plus any IR voltage drop losses in switching devices and PWM filtering.

For 240vac, the minimum is about 350vdc. 240vac AIO typically run their HV DC bus between 380 vdc and 500 vdc. The HV DC filter capacitors will slump in voltage a bit during peak load currents of AC sinewave peak. HV DC bus electrolytic capacitors typically have a 500 vdc maximum rating.

For 120vac AIO, the minimum is about 200 vdc. 120vac AIO typically run their HV DC bus between 220 vdc and 300 vdc. HV DC bus electrolytic capacitors typically have a 315 vdc maximum rating.

The low-cost HF AIO's run their PV SCC as a boost only converter so the PV input voltage cannot exceed the inverter HV DC bus. There are some that have an additional forward converter stage between PV SCC HV DC output and inverter HV DC bus (typically 500vdc to 250vdc conversion). This adds a couple of percent additional power loss due to the extra intermediate converter, but it allows SCC to run PV input array at higher DC voltage than inverter HV DC bus and provides galvanic isolation between PWM sinewave AC chopper and PV input terminals that is not provided on low-cost HF inverters. On low-cost HF inverters the two PV pos and neg terminals are riding on top of the polarity chopping inverter HV DC bus which is why you must use double pole DC PV breakers to break both the PV pos and neg lines.

This intermediate PV path converter is a necessity for U.S. 240/120vac split phase HF inverters which are two series connected 120vac inverters with two independent HV DC buses. The intermediate converter allows the PV power to be shared to both independent HV DC buses and provides isolation between the two internal HV DC buses and PV input terminals.

The PV SCC boost converter has better efficiency when PV array voltage is nearer the inverter internal HV DC bus voltage, but since Vmp is typically 0.81 to 0.85 of Voc and you cannot let Voc of PV array to get above inverter HV DC bus, the closest you can run PV Vmp is about 85% of inverter HV DC bus.

Hi!

The specs for most these MPPT working voltage AIO is 120-400V, but they state MAX open volt 450, sometimes they state 160-350V working range with 400V max. But I just got a reply from the company and some friends that they say they run at 200-215volts and it works , the company says although it will run batteryless no problem at 200V and above , the ideal for efficiency is closer at 250-350V, they dont provide any efficiency numbers or curves though.

I live in EU.

Ive read somewhere 97% efficiency at close 300- 350V if I remember correctly

Am I missing something ?

Thanks!

 

[mrzed001]

Hi,

What exactly does "PE-N relay is missing !!!" mean ? I know what a relay does but not what a PE-N relay is.

See, this is how an inverter is built. (sometimes only with 1 relay on the grid side)
And there is the PE-N relay on the right side.
If you are in battery mode, grid is disconnected ... so the grid Neutral is disconnected too.
Your output neutral is so not connected to Earth. It was on grid side with the Bond.
And you need to make your own bond in this case.
These is the job for the PE-N relay.
And if connects, no more floating ground.

Can you show me proof that EASun are missing these relays while the same model from MPP does have it ? All the ones we opened , similar models , where the exact same inside, definitely made in the same factory.

I do not think so.
Here users ordered a lot of EASun products.
Even the ones look line MPP Solar are not exact copies.

And the SML II (blue-white), SMR II, ... these products are less identical copies.
The SML II does not have a PE-N relay (I know because I tested 2 of them)

Ive read somewhere 97% efficiency at close 300- 350V if I remember correctly

The ideal is 320Vmpp solar string for the inverters. And Voc below 450V.

 

[8_Hz_WAN_IP]

What would be the electrical difference between this, and diy grid tie with a 3000 min-tlx?

 

[EliteSolar]

View attachment 107566
See, this is how an inverter is built. (sometimes only with 1 relay on the grid side)
And there is the PE-N relay on the right side.
If you are in battery mode, grid is disconnected ... so the grid Neutral is disconnected too.
Your output neutral is so not connected to Earth. It was on grid side with the Bond.
And you need to make your own bond in this case.
These is the job for the PE-N relay.
And if connects, no more floating ground.





I do not think so.
Here users ordered a lot of EASun products.
Even the ones look line MPP Solar are not exact copies.

And the SML II (blue-white), SMR II, ... these products are less identical copies.
The SML II does not have a PE-N relay (I know because I tested 2 of them)


The ideal is 320Vmpp solar string for the inverters. And Voc below 450V.

Hi,

thanks for your explanation. In the end I ordered EASUN 3.6kw SMG II for 420euros . I have no idea if they have the PE-N relay but since Im not gonna use any batteries I guess this is not a problem, but I can certainly find out when it arrives if you want.

What would be the electrical difference between this, and diy grid tie with a 3000 min-tlx?

I am not sure I understasnd the question , but arent these all clones more or less ? The model you are refering can export to grid ( similar to EAsun SV II ) , an extra future I dont need ?

 

[Lucasss]

Hi,

thanks for your explanation. In the end I ordered EASUN 3.6kw SMG II for 420euros . I have no idea if they have the PE-N relay but since Im not gonna use any batteries I guess this is not a problem, but I can certainly find out when it arrives if you want.


I am not sure I understasnd the question , but arent these all clones more or less ? The model you are refering can export to grid ( similar to EAsun SV II ) , an extra future I dont need ?

Have the pe-n relay sml II version?

 

[mrzed001]

Hi,

thanks for your explanation. In the end I ordered EASUN 3.6kw SMG II for 420euros . I have no idea if they have the PE-N relay but since Im not gonna use any batteries I guess this is not a problem, but I can certainly find out when it arrives if you want.

If there is a blackout your inverter will give you power from PV
It is a solar UPS after all
And there will be floating ground

 

[EliteSolar]

That's correct and I can verify this behaviour. The only correct solution, as far as I understand, is to use an external grounding box , which still makes this AIO a fantastic value. Its a month Im using it and it works great

 

[Tony54]

Hi guys,
Im love learning from your knowledge, it's quite heavy reading at times and I need a few passes to understand things.
A couple of questions if I may. Im keen on buying the Seasun agm2, 3.6 kw. (on offer 450euro)
1.My roof space restricts me to 6 x 460w panels, vm 42v and voc 50v so that gives me only total vm of 252 v and voc of 300v. I know there aren't any graphs of efficiency but how much losses do you think I may have. It won't be a great problem to me as I can put some more panels on my East side roof to compensate and using a scc to feed the battery direct.
2. Im still not sure about the earth bonding for my intended Easun system, with 5 kw of lifepo4. Could you elaborate a bit more. I will be using a mains grid input for battery charging and for supplementing lack of solar and or battery and so assume that will earth the inverter. Then I assume that the panels should be grounded to a separate ground Spike.
Do you think I will need an earth ground box?
Moving on, I had read about 'batteryless' inverters as it would work well here in s Spain, but thought it was a bit, wishy washy, so bought 8 230ah batteries from china, Docan. But now having read your experiences, I am sold on the idea. I will use my batteries but when they die off I can alway use the system without battery's. I'm sure by this time battery less inverters with grid backup will be very well established

 

[EliteSolar]

1) Good luck with absolute numbers but I would say its not that bad. The problem is really when its really cloudy and I only know for my 3.1kw 340VOC system . Its not that bad probably anyway . I wouldnt worry about efficiency numbers . It should work OK
2) The problem with the inverter is that the NG bond from the grid is interanlly bonded to the ac output of the inverter . That means when you use the inverter battyreless WITH ac in grid it will be fine until the grid goes down ( not only L but N too ) and your system then will be ungrounded . This is also the case with abttery without AC GRID . But if you never connect to ac grid you can just bind the N to the G on the inverter outputs . Now if you need a ground rod/spike I dont know about that and its a heated debate . From what I understand ground rods are not the best for all cases , for example with marine boats or RVs its impossible to earth it to a ground spike/rod but they are still fine ( people ground it to the battery negative for example ) . Look it up for more info , I am not an expert on grounding. But yes you will need a ground box incase the the grid goes down , your system will be ungrounded ( but some people claim thats fine if you use an RCD , I'm not sure about that I have read confilicting reports so make sure you do your research, most people say its not fine ) .

The problem with batteryless systems is that you really cannot control your load if you dont want to spend extra money on the grid. For example the system starts in the morning with 300watt , peaks around noon to 1.8kw then goes down to 300watt , how do you connect an aircondition to have it run for free ? the only way not to loose power is to have your loads higher than the produced energy. If you dont you lose energy and if you do , you pay to the grid. Although we all expect this kind of behaviour , for most realistic scenarios its best to have a battery to save the excess energy you produce ( because you cannot control the power of the loads , well you can but these are only specific scenarios , for example you run bitcoin miners all day or you heat the pull either way so the PV is there just to reduce the overall bill , but thats now how all people approach it ).

Overall it works really good with my 340VOC and as expected . So yeah it makes sense to use the batteries also , I have a special case where I can control my loads so it doesnt really matter if I have batteries . I will need some soon though cause Im moving to a campervan , Im leaving the house.

Cheers

 

[Tony54]

Gracias Elite, Thanks for your thoughts, lots to digest. I will have a look at grounding boxes.
Good luck with your move.

 

[mrzed001]

Hi guys,
Im love learning from your knowledge, it's quite heavy reading at times and I need a few passes to understand things.
A couple of questions if I may. Im keen on buying the Seasun agm2, 3.6 kw. (on offer 450euro)
1.My roof space restricts me to 6 x 460w panels, vm 42v and voc 50v so that gives me only total vm of 252 v and voc of 300v. I know there aren't any graphs of efficiency but how much losses do you think I may have. It won't be a great problem to me as I can put some more panels on my East side roof to compensate and using a scc to feed the battery direct.
2. Im still not sure about the earth bonding for my intended Easun system, with 5 kw of lifepo4. Could you elaborate a bit more. I will be using a mains grid input for battery charging and for supplementing lack of solar and or battery and so assume that will earth the inverter. Then I assume that the panels should be grounded to a separate ground Spike.
Do you think I will need an earth ground box?
Moving on, I had read about 'batteryless' inverters as it would work well here in s Spain, but thought it was a bit, wishy washy, so bought 8 230ah batteries from china, Docan. But now having read your experiences, I am sold on the idea. I will use my batteries but when they die off I can alway use the system without battery's. I'm sure by this time battery less inverters with grid backup will be very well established

Not recommending EASun. Not because it is a cheap clone of the MPP Solar inverter.
But we had a lot of problems with them. Loose screws making short circuit inside. Cables not connected in the inside. Dead on arrival ... etc.
And EASun does not like to replace it under warranty. If you fight for it ... maybe.

Other people had problems too
https://easunpower-nomore.eu/

Use an MPP Solar (Voltronic Axpert). It has inner PE-N relay, and has support and warranty.