Adding another 5.7kw solar to my power wall that already has 5.7kw

[Icepicknz]

Hey guys.

I'm installing a second lot of solar to my home that has a single powerwall2 where i have an existing 5.7kw array.
Apparently the installer is telling me that I need to wire the second 5.7kw direct to the backup gateway as in the event of a power cut the inverter in the power wall can't handle more than 7.X kw load to charge.

Anyone have experience with this?

Many thanks

 

[cwied]

I don't have direct experience with this, but I've seen it discussed before. Each Powerwall can only charge at 5 kW continuous, so they won't install more than that on the backed up side. I'm assuming there's some adjustment for house load, AC vs. DC and also solar efficiency. You'd need a second Powerwall in order to handle all your solar production.

 

[Icepicknz]

Yeah; i don't mind the feeding back to the grid any excess over 5kw; its more to cater for winter time when there is less sun light. The thing is I didn't realise they would have to isolate it; i have seen a video of an ozzie bloke where he tested off grid and when the power wall was reaching 70-90% it would change the frequency which would tell the solar inverter to back off or shutdown so it didn't provide more energy than the battery could consume. Just wondered if it would do the same thing in this type of event

 

[cwied]

I think the issue is that if the grid drops in the middle of the day when your solar system is generating more than the Powerwalls can handle, you'd be in trouble when the gateway disconnects you from the grid. It also seems like right now the Powerwalls can't tell the solar inverter to back off - it's only off and on. That means the solar would overload the system if it comes on during high production times. If the Gateway could control the solar production more precisely, I think it would probably be possible to do what you want.

 

[Icepicknz]

Fair enough, thanks for your input; so i guess i just let them wire the second lot of solar to the backup gateway directly for safety.

 

[GenSao]

FYI, the Tesla FAQ states:

How large a PV system can I connect with one Powerwall?
To ensure reliable operation during grid outages, at least 1 Powerwall is required for each 7.6kW AC of solar included in the backup circuit.

 

[Icepicknz]

FYI, the Tesla FAQ states:

perfect thanks, exactly what i was looking for