AC coupled using EV battery and small buffer bank

[PigBodine]

Wondering your thoughts on this idea.

I have a 4.8kW nameplate grid tie system with 15 IQ7+ inverters, so 4.4kW. The most power I have ever seen is 3.9kW.

I would like to add a backup power function and currently have a 65kW battery sitting in my garage in my Chevy Bolt. Many have wired a 1kW 12V inverter to the car which can run continuously for days.

I have a meter main to 2 subs. The main house sub would be the "critical load panel". I already have a transfer switch between the meter main and the critical load panel. We have a very efficient house without electric heating or cooling and our house load is low, 13kWh max per day, likely half that in an outage. Our grid is fairly reliable.

The cheapest option is standard 4-6kW sine wave inverter fed by a small battery bank (100ah 24v?) without integrating solar. This would handle startup loads for fridge, freezer, etc. The small bank would be topped by a charger from the EV battery inverter. I could do DC-DC charge controller but would like to have an inverter anyway for the car to run tools, etc.

I would like to integrate solar, potentially to charge the EV as well. This means hybrid inverter/charger capable of AC coupling. I would like to keep my inverter bank small for cost control because, as above, I already have a large 65kW reservoir.

My question is:

1) Is there an inverter/charger 4-6kW that is capable of AC coupling and immediately dumping a large PV inrush current to ground or somewhere besides the battery? Or disconnecting if there is a load dropout and/or sudden increase in power output from the array?

For more gradual power ramp up or down I believe I can use frequency shift with the IQ7's. Most systems I've looked into require a large battery bank to handle the above situation and the battery would be grossly oversized for what I am trying to do. Ideally the hybrid inverter would be able to handle a concomitant generator input (the EV inverter input) and potentially have an MPPT input for additional solar but these aren't absolute requirements.

Thanks for your help, this forum seems great!

 

[PigBodine]

Another idea that may be equal in cost but add solar capacity.

In the case of outage shut off half the current array at the Enphase combiner box, leaving 8 IQ7's available to AC couple, likely around 2kW max power.

To build out the system I would then add 4 or so DC coupled panels to a multimode inverter with MPPT input that can also AC couple with the IQ7's. A 24V battery bank would then only have to handle inrush of 2kw/24V = 83A meaning about 160ah to keep it a 0.5C. Could potentially drop battery capacity even more if I kept a lithium bank at 50-80% SOC, correct?

Any recommendations for an inverter that could handle this scenario, plus a "generator" input from the EV? During the majority of the time grid-up it would be adding to the current array and spinning the meter backwards.

Should mention that transfer to backup doesn't need to be instant, the current transfer switch is manual.