I have a solar system with an on-grid (grid-tie) inverter, which only works when there is an active grid supply. Unfortunately, I live in an area where there's no grid power for most of the day, so my solar setup goes unused during that time.

Buying a new hybrid inverter is quite expensive and would make my existing on-grid inverter a waste, which I want to avoid.

Here's what I’m thinking:

• I have a 12V 150Ah battery bank connected to a pure sine wave inverter, which generates a stable 230V AC output.
• I'm considering disconnecting my solar inverter from the actual grid and connecting it instead to the output of the battery inverter.
• This would act as a “fake grid” to simulate grid presence, tricking the on-grid inverter into syncing and starting solar power production.
• Then I would run my AC loads using the combined output from both the solar inverter and the battery inverter.

My questions:

1. Is this approach safe and practical for DIY use?
2. What are the risks of backfeeding from the on-grid inverter into the battery inverter?
3. How can I protect the battery inverter from overcurrent or overvoltage due to solar surplus?
4. Are there proven dump load controller circuits or open-source solutions to balance this kind of setup?

 

No it's unlikely to work. Grid-tie inverters need to qualify the utility power before output. Your small inverter won't be able to provide the needed stability and current sink abilities.

It's dangerous and likely to destroy your equipment if by some fluke it did qualify the power source.

 

This is pure speculation, but…

The impedance of the grid will be very different than that of your sine wave inverter. This would likely throw off the control mechanism of the inverter causing wild swings in voltage as it tries to adjust.

 

Thank you all for quick responses.
What if i use battery inverter with 3Kw power? if equipment needs more power thats not fulfilled by combining battery inverter+solar inverter then battery inverter will trip and shutdown, so not risk with my knowledge I am not expert, i am hobbyist.

 

Thank you all for quick responses.

What you can do is to buy a cheap Chinese hybrid grid-tie inverter. They will run on batteries or solar panels. Your do need the proper AC breaker and DC fusing when using these cheap GTI inverters. I've been testing several types with my hybrid solar/battery system. These inverters need at least 24VDC. https://www.aliexpress.us/item/2251...st_main.5.25161802OiNMFX&gatewayAdapt=glo2usa


https://forum.allaboutcircuits.com/...rge-controller-datalogger.194146/post-1884696

 

Thanks you all.

 

Why don't you use the solar panels to charge the battery?

 

I have a solar system with an on-grid (grid-tie) inverter, which only works when there is an active grid supply. Unfortunately, I live in an area where there's no grid power for most of the day, so my solar setup goes unused during that time.

Buying a new hybrid inverter is quite expensive and would make my existing on-grid inverter a waste, which I want to avoid.

Here's what I’m thinking:

• I have a 12V 150Ah battery bank connected to a pure sine wave inverter, which generates a stable 230V AC output.
• I'm considering disconnecting my solar inverter from the actual grid and connecting it instead to the output of the battery inverter.
• This would act as a “fake grid” to simulate grid presence, tricking the on-grid inverter into syncing and starting solar power production.
• Then I would run my AC loads using the combined output from both the solar inverter and the battery inverter.

My questions:

1. Is this approach safe and practical for DIY use?
2. What are the risks of backfeeding from the on-grid inverter into the battery inverter?
3. How can I protect the battery inverter from overcurrent or overvoltage due to solar surplus?
4. Are there proven dump load controller circuits or open-source solutions to balance this kind of setup?

Hi,

It's an interesting idea but will take some doing.

First, the grid will look like a voltage source that has low impedance, and because it might be considered near ideal it will be able to take as much current as you can pump into it, up to the breaker ratings of course.
Your battery inverter may not be able to act like that, and it's unlikely that it will ever act like that when it has no load. There would have to be significant load, enough so that the solar inverter will always have enough load to be able to absorb all the power it can produce.
I can't say for sure this would work even like that though.

A grid tie inverter looks more like a current source than a voltage source. There is usually a secondary mode though where it will go through a voltage mode first, before it actually ties into the line. I say "usually" because I don't know if they all do that or not. I do know the ones I worked on many years ago did do that. They start up in voltage mode, then connect to the line and switch into current mode output. They then supply as much current as they are able to.
So you can check and see if there is a voltage mode associated with yours and perhaps you can get it to stay in that mode, if that helps. Either that or you have to try the above.

Whatever you do I can't be sure it would work without a detailed schematic of everything.