Sense check my upgrade plan

[East/West]

Hi everyone.
I currently have 8.4KW of panels working away nicely on an E/W split.
Grid tied with a Hypontech 6KW Hybrid inverter. DIY install of course.
My plan was just to add a battery and be done but I've since found the Hypontech only supports expensive HV Batteries not the DIY battery I would like to build.

Plan B is to add 7/6 cheap 350w to my south facing garage roof and install a 3.6kw SunSynk Hybrid inverter in the garage.
Then add 15kw of DIY Lifepo4 batteries later (i'd rather the batterys not be in my attic to be honest)

I supposed my question.......and this might be a silly to some.
Will the 2 systems play nice together considering they wont be talking to each other ?
For example, Say the SunSynk is not producing will it still charge the battery with the excess from the Hypontech ?
I will have all CTs etc in place.

I think I know the answer is yes but I'd like to be sure !

Thanks

East/West (and hopefully South.......)

 

[DIYrich]

Don't know anything about hypnotech nor sunsynk. If one is ul1741 listed, and the other can frequency shift, then you can have one be AC PV into the other.

If you are going to buy another inverter anyway, why not just buy one that can do it all? Keep the hypnotech as backup.

 

[East/West]

@DIYrich Thanks for the input.
I'll do some research on ul 1741 & fq shift.
I had considered replacing the Hypontech with an equivalent Sunsync. Then putting the Hypontech in the garage.
Getting the batteries out of the house would be a bonus for me. Not wanting to start a debate on that one......
Also adding a smaller hybrid would be a much cheaper option.

Before I mounted the panels on my house I "practiced" by installing rails on the garage so its ready to rock.

 

[DIYrich]

How far away are the two inverters? I think it is hard for the 2nd inverter with a battery to know when there is excess power on the 1st inverter to charge the battery. Similarly, hard for first inverter to know if it takes power from the second inverter, is that solar or battery.

I would be interested to hear how others have put batteries on a 2nd inverter that the 1st inverter can use.

 

[East/West]

I don't think the physical distance (within reason ) will matter . but they are fairly close. 25m

"Similarly, hard for first inverter to know if it takes power from the second inverter, is that solar or battery"
The first inverter will not have batteries so it will only ever give to system.

I think (yes think!) that as long as the 2nd inverter can see excess to the grid it should divert to the battery.

Say for example.

House is using 500w
1st inverter is producing 1kw,
2nd inverter is producing 1kw.
Will the 2nd inverter only charge the battery at 1kw , or will it charge at 1.5kw
I think I need to look at the sunsync manual......

I'm not too worried about discharging the battery.

Thanks

 

[shadowmaker]

How far away are the two inverters? I think it is hard for the 2nd inverter with a battery to know when there is excess power on the 1st inverter to charge the battery. Similarly, hard for first inverter to know if it takes power from the second inverter, is that solar or battery.

I would be interested to hear how others have put batteries on a 2nd inverter that the 1st inverter can use.

I just feed my hybrid Deye's (=Sunsynk, Sol-Ark) GEN PORT with my grid tied inverter's output. Deye then decides what to do with that "excess" power: sell to grid/power my loads/charge batts. Even without AC coupling these inverters, Deye can "sense" grid tied inverter through CT coils, but if grid tied power is greater than loads, it can't utilize that power and excess is sold to grid.

 

[DIYrich]

I just feed my hybrid Deye's (=Sunsynk, Sol-Ark) GEN PORT with my grid tied inverter's output. Deye then decides what to do with that "excess" power: sell to grid/power my loads/charge batts. Even without AC coupling these inverters, Deye can "sense" grid tied inverter through CT coils, but if grid tied power is greater than loads, it can't utilize that power and excess is sold to grid.

It appears you have the Main Panel connected to the inverter with the batteries. Original Poster's situation is the opposite. That's the problem.

 

[DIYrich]

I don't think the physical distance (within reason ) will matter . but they are fairly close. 25m

"Similarly, hard for first inverter to know if it takes power from the second inverter, is that solar or battery"
The first inverter will not have batteries so it will only ever give to system.

I think (yes think!) that as long as the 2nd inverter can see excess to the grid it should divert to the battery.

Say for example.

House is using 500w
1st inverter is producing 1kw,
2nd inverter is producing 1kw.
Will the 2nd inverter only charge the battery at 1kw , or will it charge at 1.5kw
I think I need to look at the sunsync manual......

I'm not too worried about discharging the battery.

Thanks

The problem is: It is hard for the Garage Inverter to see what is going to the House from the House Inverter.

Without batteries, Garage Inverter sends everything to the House Inverter, and the House Inverter figures it all out. That is AC PV into the House Inverter.

The problem is putting batteries on the Garage Inverter. It is difficult for the Garage Inverter to figure out how much to send to the House Inverter, and how much to put into the Battery. Then, when there is no PV, how much should the Garage Inverter send to the House Inverter from the battery?

Option 1:
Grid line to Garage Inverter. Load line from the Garage Inverter to the Grid input of the House inverter. That requires 2 beefy AC Lines (4/0?)

Option 2:
AC line between Garage Inverter and House Inverter. 8awg for 20 amps of 240v AC?
Separate battery wire from the garage to the House Inverter. That is why I asked about distance. I think with 3/0 wire, you can send 100 amps of battery power at 48v with a 3% voltage drop.

Option 1 requires an inverter that can pass through full grid power, and all the smarts.
Option 2 has the house inverter doing all the smarts with a simple UL1741 compliant garage inverter.

 

[East/West]

Looks like my plan will work perfectly.
Watch this video from sunsync.
6 minute mark

 

[East/West]

I'd just like to update for others.
I ended up getting a used 5kw hybrid solis inverter and 2.6kws of extra panels.
Up and running 2 days now.

Absolutely no issues with them.
Everything works as expected.
The smaller solis system just does it thing and the hypontech looks after the grid limiting .

Am able to monitor the two systems as one via my Zappi car charger.