Fronius Symo 20 kw three phase grid tied inverter

[Frans123]

Hi

I had my Fronius Symo 20 kw grid tied inverter (3 phase) installed with 8kw Trina 305 watt solar panels

1. phase 2 is that I now want to install batteries for night time use but also as a backup if our electricity provder sheds loads - up to +- 24 hours
2. I bought 24 batteries (2.2 volt and 875 amp hr each) which I want to connect to give me 48 volts and 1750 amp hours (bought these batteries at a very very special price from a reputable supplier)
3. my question is what more will I require (e.g inverter, charger etc) to connect the batteries to the Symo inverter (remember it is a 3 phase system)
4. I would just like some short explanation on how to do it

Kind regards

Frans

[ButchDeal]

Hi

I had my Fronius Symo 20 kw grid tied inverter (3 phase) installed with 8kw Trina 305 watt solar panels

1. phase 2 is that I now want to install batteries for night time use but also as a backup if our electricity provder sheds loads - up to +- 24 hours
2. I bought 24 batteries (2.2 volt and 875 amp hr each) which I want to connect to give me 48 volts and 1750 amp hours (bought these batteries at a very very special price from a reputable supplier)
3. my question is what more will I require (e.g inverter, charger etc) to connect the batteries to the Symo inverter (remember it is a 3 phase system)
4. I would just like some short explanation on how to do it

Kind regards

Frans

You are far better off designing and going with a bimodal system from the start than trying to retro fit batteries to a non-battery system. You now have two options, convert to bimodal inverter, set up an AC coupled system.
Both have about the same costs. You will need to purchase an inverter and DC fuses, wiring etc for both.
With one set up you will disconnect the Symo and sell it to purchase some Charge controllers, With the other you will keep the symo and not get any charge controllers but will be playing with trying to keep the two inverters sinced.
Outback inverter will work in either case. The Radian series will probably be a good fit and can AC couple with most grid tie inverters.

[Frans123]

You are far better off designing and going with a bimodal system from the start than trying to retro fit batteries to a non-battery system. You now have two options, convert to bimodal inverter, set up an AC coupled system.
Both have about the same costs. You will need to purchase an inverter and DC fuses, wiring etc for both.
With one set up you will disconnect the Symo and sell it to purchase some Charge controllers, With the other you will keep the symo and not get any charge controllers but will be playing with trying to keep the two inverters sinced.
Outback inverter will work in either case. The Radian series will probably be a good fit and can AC couple with most grid tie inverters.

thank you for your reply - I had my sysytem installed a week ago and it really costed me a lot of money
the bimodal system is not an option
would it be too much to ask to explain in a bit more detail the purchase of another inverter with DC fuses
also how will I charge the batteries without an charge controller

sorry for asking for detail but I am new to this and just want to tell my installer exactly what I want

regards

Frans

[ButchDeal]

thank you for your reply - I had my sysytem installed a week ago and it really costed me a lot of money
the bimodal system is not an option
would it be too much to ask to explain in a bit more detail the purchase of another inverter with DC fuses
also how will I charge the batteries without an charge controller

sorry for asking for detail but I am new to this and just want to tell my installer exactly what I want

regards

Frans

You will be making a bimodal SYSTEM either way. It is just cheaper to go that way from the start ( no need for the Symo inverter. So with an AC coupled system the batteries are charged using the inverter, the outback inverter is both an inverter and a charger. So you should figure out how much power you want to be on backup owner and if that is three phase or one phase, And if one phase do you need 240 or just 120v. This is just for the backup circuites. If you need three phase then you will want three outback inverters to get it. Also how many fronius inverters do you have? Like I said AC coupled is going to be complicated to design, I can only guess at what you have so far.
But in general, assuming you have one Symo inverter 240/208V then you would be ok with a radian inverter from outback. Both systems would only be single phase. The radian inverter would have one AC connection to the Symo, another to an emergency panel that will stay up when grid is down, and you would need a disconnect from the grid. When the grid is down the radian will provide a reference voltage for the Symo inverter to come on. Extra power goes to the batteries till they are full, then the radian will disconnect from the Symo which will cause it to turn off. When the batteries are drawn down it will reconnect to the Symo and provide the reference voltage again till the batteries are full again.....
Kind of a simplification .....

[Frans123]

You will be making a bimodal SYSTEM either way. It is just cheaper to go that way from the start ( no need for the Symo inverter. So with an AC coupled system the batteries are charged using the inverter, the outback inverter is both an inverter and a charger. So you should figure out how much power you want to be on backup owner and if that is three phase or one phase, And if one phase do you need 240 or just 120v. This is just for the backup circuites. If you need three phase then you will want three outback inverters to get it. Also how many fronius inverters do you have? Like I said AC coupled is going to be complicated to design, I can only guess at what you have so far.
But in general, assuming you have one Symo inverter 240/208V then you would be ok with a radian inverter from outback. Both systems would only be single phase. The radian inverter would have one AC connection to the Symo, another to an emergency panel that will stay up when grid is down, and you would need a disconnect from the grid. When the grid is down the radian will provide a reference voltage for the Symo inverter to come on. Extra power goes to the batteries till they are full, then the radian will disconnect from the Symo which will cause it to turn off. When the batteries are drawn down it will reconnect to the Symo and provide the reference voltage again till the batteries are full again.....
Kind of a simplification .....

Thank you
I think I understand better since your second explanation
This is all new to me and I must go and google some of the info but what I can read between the lines it can be done to use the batteries at night without using the grid
Thank you once again

[ButchDeal]

Thank you
I think I understand better since your second explanation
This is all new to me and I must go and google some of the info but what I can read between the lines it can be done to use the batteries at night without using the grid
Thank you once again

Wait what? Are you trying to go off grid? Or have some power when the grid is down? Or other option, handle loss of net metering ( grid zero, not feeding into the grid)?

Outback has some documents on their site about AC coulee systems. AC couled systems are rare so few people with experience and yours is 3phase so even less experienced people.

[Frans123]

Wait what? Are you trying to go off grid? Or have some power when the grid is down? Or other option, handle loss of net metering ( grid zero, not feeding into the grid)?

Outback has some documents on their site about AC coulee systems. AC couled systems are rare so few people with experience and yours is 3phase so even less experienced people.

it seems like I really stepped into it--- I was going into this a little blind and because solar energy is such an unknown field I just wanted to reduce my electricity bill which is very high
thank you for the info = I will have to go and google the AC coulee system
i really thought it was just just as simple as to buy the inverter and batteries and off you go

[catherinelirian]

Reply

Hi

I had my Fronius Symo 20 kw grid tied inverter (3 phase) installed with 8kw Trina 305 watt solar panels

1. phase 2 is that I now want to install batteries for night time use but also as a backup if our electricity provder sheds loads - up to +- 24 hours
2. I bought 24 batteries (2.2 volt and 875 amp hr each) which I want to connect to give me 48 volts and 1750 amp hours (bought these batteries at a very very special price from a reputable supplier)
3. my question is what more will I require (e.g inverter, charger etc) to connect the batteries to the Symo inverter (remember it is a 3 phase system)
4. I would just like some short explanation on how to do it

Kind regards

Frans

I had my Fronius Symo 20 kw grid tied inverter (3 phase) installed with 8kw Trina 305 watt solar panels