Add Battery Backup To Existing Solar system

[spacemancw]

Hi, I'm sure this question has been asked before, apologies. I have read a lot, googled and you-tubed. I seem to get bits and pieces, but not the whole picture.

I have 28 solar panels, I believe the panels are 305 w each (HANWHA Q CELLS Q.PEAK-G4.1 305 305W MONO SOLAR PANEL).
That's over 8000W. The inverter is a grid-tied SolarEdge. We use the solar power, and send excess to the grid. We then use Grid power at night.
When the Grid goes out, the solar goes out.
I have a 6500W gas generator. I have that coming into the main panel on a 30amp breaker. There's a manual interlock, such that I turn off the main breaker from the Grid, slide the interlock over, and I can turn on the generator breaker. When the generator is on, I can see the Inverter trying to start up but then fails with a startup error. I'm sure the power generated by the generator is unstable and the inverter doesn't like it. Wrong frequency.

So I want to install a battery for night use and backup. I want to make sure I understand how this works and and what exactly (roughly) I need.
I will need a battery pack connected to an additional Inverter. That Inverter will then be connected to the electrical panel. (just going to use main panel for simplification, no critical-use panel at the moment).

What I hope will happen : with solar power generated during the day, the house will be powered, the batteries will be charged, and excess, if any, goes to the grid.
At night, no solar generated, so the new Inverter draws power from the battery, then from the grid if needed. Hopefully no grid needed as power consumption should be low at night.
When the grid is down, the new Inverter detects it, draws enough power from the battery to tell the grid-tied inverter that power is up, and the grid-tied inverter comes back on (after the timeout) and continues drawing power from the solar panels, powering the house and charging the batteries. If there is excess power, what happens to that if the batteries are charged and the grid is out? At night, we'd use the battery power.

So if this is all correct, I am looking for advice on what I need to buy. I will not be touching the grid-tied inverter, so for the new Inverter, I don't think I need a hybrid inverter, just an off-grid converter, correct? What size? I was thinking 10,000W. Maybe 12,000W? Any brand recommendations?
Also I would like to tie my gas generator in to the setup. I reckon it would go into the new Inverter first.

What kind of battery and what size? I guess battery power should match the Inverter? My main objective is to use the battery at night instead of paying the Grid electrical company., or at least reduce what I use from the grid at night.

Below are my simplified diagrams for how this is wired now, and would be wired.




I have a sump-pump and a well-pump. I would want them to run. Also air-fryer, microwave, waste-disposal. The rest would be normal lights, TV, fridge, wifi.

Thanks in advance for any help, advice and/or corrections.

 

[DIYrich]

How will New Inverter know how much Solar Power is being produced so the excess can be stored in the battery?

One route is to go the Solaredge Home Backup Interface. Then you have expensive Solar Edge batteries.

Another option is to put an EG4 18k pv or Sol-Ark between the Grid Tied Inverter and the Electrical Panel.

Battery power is more dependent upon Load than on the Inverter. Although, you do size the Inverter for the Load. You may want enough battery to last at least 1 day with no grid and no solar (rainy).

Using the Solaredge when the grid down is complex. Home Backup, 18k pv, Sol-Ark can handle it. Other inverters may not.

 

[Bleedingblue]

Hi, I'm sure this question has been asked before, apologies. I have read a lot, googled and you-tubed. I seem to get bits and pieces, but not the whole picture.

I have 28 solar panels, I believe the panels are 305 w each (HANWHA Q CELLS Q.PEAK-G4.1 305 305W MONO SOLAR PANEL).
That's over 8000W. The inverter is a grid-tied SolarEdge. We use the solar power, and send excess to the grid. We then use Grid power at night.
When the Grid goes out, the solar goes out.
I have a 6500W gas generator. I have that coming into the main panel on a 30amp breaker. There's a manual interlock, such that I turn off the main breaker from the Grid, slide the interlock over, and I can turn on the generator breaker. When the generator is on, I can see the Inverter trying to start up but then fails with a startup error. I'm sure the power generated by the generator is unstable and the inverter doesn't like it. Wrong frequency.

So I want to install a battery for night use and backup. I want to make sure I understand how this works and and what exactly (roughly) I need.
I will need a battery pack connected to an additional Inverter. That Inverter will then be connected to the electrical panel. (just going to use main panel for simplification, no critical-use panel at the moment).

What I hope will happen : with solar power generated during the day, the house will be powered, the batteries will be charged, and excess, if any, goes to the grid.
At night, no solar generated, so the new Inverter draws power from the battery, then from the grid if needed. Hopefully no grid needed as power consumption should be low at night.
When the grid is down, the new Inverter detects it, draws enough power from the battery to tell the grid-tied inverter that power is up, and the grid-tied inverter comes back on (after the timeout) and continues drawing power from the solar panels, powering the house and charging the batteries. If there is excess power, what happens to that if the batteries are charged and the grid is out? At night, we'd use the battery power.

So if this is all correct, I am looking for advice on what I need to buy. I will not be touching the grid-tied inverter, so for the new Inverter, I don't think I need a hybrid inverter, just an off-grid converter, correct? What size? I was thinking 10,000W. Maybe 12,000W? Any brand recommendations?
Also I would like to tie my gas generator in to the setup. I reckon it would go into the new Inverter first.

What kind of battery and what size? I guess battery power should match the Inverter? My main objective is to use the battery at night instead of paying the Grid electrical company., or at least reduce what I use from the grid at night.

Below are my simplified diagrams for how this is wired now, and would be wired.

View attachment 210767



I have a sump-pump and a well-pump. I would want them to run. Also air-fryer, microwave, waste-disposal. The rest would be normal lights, TV, fridge, wifi.

Thanks in advance for any help, advice and/or corrections.

I'd get rid of the solar edge if it was me. I've had to eat my losses on equipment that was the wrong equipment when I purchased them.
Get an inverter that is able to charge batteries and push current to the grid when there is an excess

 

[spacemancw]

I'd love to get rid of the SolarEdge. It's not mine, the whole set up is leased. I don't wanna touch it. But I do want to trick it into thinking the Grid is up when it's not. And I wanna use battery power at night.

 

[WrenchLight]

There are inverters available that can interface with existing grid-tied solar. Unfortunately, you'd need to buy a hybrid inverter along with the battery.

You don't want to connect the grid-tied solar to a generator. If the inverter ever is successful in sending power to the generator, it could damage it. The grid-tied inverters usually have a narrow frequency range before they'll connect, like 59.5 to 60.1 Hz. It's a good thing the generators are usually not exactly on the right frequency.

The way the new inverter would be able to store energy in the battery is by using current transformers (CT) near the utility meter to measure total home consumption. That way it can calculate how much it can charge the battery or how much to generate from the battery to try and keep the home current at the CTs zero unless the battery is full and there is enough solar to sell back.

Some hybrid inverters allow the grid-tied inverter to connect to their generator port and keep the grid-tied solar on even when the grid goes down. But it'll shut off the grid-tied inverter when the battery gets full because there's nowhere for the solar to go. (Can't sell back solar when the grid is down.)