Multiple inverter, single battery

[kevdagoat]

Hi all,

I am looking at building a system using a BYD battery and Fronius Gen24 inverters (Primo) - does the battery emulator support sharing one battery between multiple inverters / would there be any issues from a technical standpoint with this approach?

The reason why I am keen is because the premises I am looking to connect only has single phase AC and most inverters for single phase max out at 10kW - simply not enough for my needs (ideally 15-20kw)

From a purely electrical standpoint I assume its pretty simple, i.e. separate contractors for each inverter would be required, as well as associated disconnects etc. (and thus the code to make this work).

I assume the main limitations are on software side?

• inverters would have to be synchronized to ensure that they were both charging/discharging at the same time (otherwise a loop could be created)
• if one inverter is charging and the other in standby, the standby inverter would see increase in SOC - could potentially fault/failsafe

(Both of these seem very achievable though through sunspec modbus, atleast for fronius)

Has anyone considered/researched this before?

[1ni3shi]

I'm assuming the 10kw max per phase is your ability to export to the grid, your home wiring might be the same or different(capable of more load). This is why the inverters are designed that way, however you can have separate inverters one for your home/battery and the other for your PV system.
Question is, is the house wired to for 15-20kw usage?

[kevdagoat]

It’s actually because I only have single phase 80A from the street and sadly I have a lot of peak power demands!! On summer nights with all ACs going, oven, HWS etc you’re looking at ~12-14kW (can’t find an inverter this big).The panel is wired for 20kW. Sadly where I live we are grid export limited to 1500w and must be part of a VPP if we want to export more than that - so no exporting here :)

[1ni3shi]

In theory this might work, have your 10kw string inverter wired to the house and grid and have your 10kw hybrid inverter connected to the string inverter.
10kw string inverter is wired to the house load and 10kw hybrid inverter is wired to back up load.

You will need to check with your local codes to see if this is acceptable

[kevdagoat]

Look I’m more talking about 2 hybrid inverters sharing one battery, no string inverters.

Like this but imagine there are 2 fronius units both sharing a battery

[1ni3shi]

If you have 1 battery attached to each inverter, your problems would be solved. It would provide up to 6 hours at max output 10kw each.
If you had 2 inverters connecting to one battery this would give you up to 3 hours of peak usage at 20kwh, and vice versa 3 hours to recharge the battery.

Will you have solar in you solar panels in your system or are you planning to charge from the grid?

[kevdagoat]

Yes that’s correct, I don’t really need 2 batteries (100kw) though, it’s mostly around handling the 30mins of peak power demands that fall into “peak pricing” - I.e. times when it’s double the cost to buy electricity.

at this stage there will be three small strings however need to do some calcs to work out how much kw I can put up - planning for around 10. Short term is pull from the grid during the middle of the day cheap pricing and store for peak pricing

[1ni3shi]

Deye has single phase hybrid inverters 12-18kw, but only support low voltage batteries.

[kevdagoat]

That’s right - sadly don’t have the space for a bunch of server rack batteries, the BYD is quite literally the perfect size for the space!!