How does an inverter use excess solar capacity to charge a DC connected battery?

Question

Given the following home solar setup:

• 10KW of solar panels
• 5KW (Fronius Gen24) inverter
• 10KWH DC attached battery

And it is a sunny day with the potential of generating a full 10WK from the solar panels.
And the battery is at 5% charge.
And the house is currently consuming 3KW

Assuming the system is configured correctly, what should happen (and why)?

1. The excess solar capacity is used to charge the DC battery:

  Then 3KW is consumed by the house
  And 7KW is used to charge the battery

2. DC charging is limited to the inverter AC capacity limit by clipping:

  Then 3KW is consumed by the house
  And 2KW is used to charge the battery

3. DC charging is limited to the max PV power of the inverter:

  Then 3KW is consumed by the house
  And 4.5KW is used to charge the battery

4. Something else: ¯\_(ツ)_/¯

References:

• Fronius Gen24 Tech Data

Answer 1

You can think of it as a 7.5 kW solar charge controller to a battery.... Plus a separate 5kW inverter... same as if you bought those components as separates. They are in a single enclosure and acting on the same battery.

So your solar production will be capped at 7.5 kW because that's all the charge controller you paid for.
Your AC output will be capped at 5kW because that's the size of your AC inverter.

In your scenario, your battery will charge at 7.5 kW and then simultaneously discharge at 3 kW, leaving 4.5 kW net charge. So 3) is the closest.