In regards to your first statement. You think this would fool the gateway even at night? Risk of hurting generator or worse, the PW? If it works and the PW fully charges up, then gateway raises frequency to shut off "solar", but generator continues pushing... drawing vs pushing?
On a totally unrelated note, since you seem to know your *sugar*, if the teslas become capable of bidirectional charging (aka v2h), would you put the HPWC breaker in the generation panel with the solar and powerwall or elsewhere? Why?
Lastly, in grid outtage scenarios, with a full battery, to prevent gateway from shutting down alll solar with > 60 Hz do you think using a dynamic ev charge rate to shed that load works fine or should I go with tesla inverters on the hope they have internal tech that can gate or stop a fraction of solar production or perhaps even utilize select mid circuit interruptors used for rapid shutdown compliance
Doing DIY hacks like this you always take your warranty and product in your own hand. I do not recommend this, but I have heard of it working.
The generator will be totally dumb to the needs of the Powerwalls, and I am not sure how the interplay of the generator, batteries, PV and Powerwalls will really work. Others may be able to give more specific advice.
The danger comes when your batteries get full and the PW start frequency shifting to turn off the source. If you can avoid that whole situation you will avoid many of the pitfalls. Certainly, there is a risk to both the generator and the PW, if either sees a signal it cannot deal with. The core of the problem is you have 2 grid-forming type inverters but neither know the limitations or needs of the other.
As far as the charging question, the location of the circuit depends on the case, likely it goes where the rest of the loads are, but if it capable of backfeed then it needs to adhere to the busbar rules in 705.12. However, if it can be controlled by a PCS setting along with the rest of the Powerwall backfeed, then it can be limited like the rest, likely using the same systems. There is simply not enough information available to make this decision accurately.
Using a dynamic EV charger that responds to a full or near full battery would be ideal. Theoretically, with a large enough battery you may never see frequency shifting, instead your EV charger is setup to charge at 85% or more PW power. Ideally this charger could manage its own draw, so that it's charging slowly when there is just a little overage, and more quickly if there is lots of excess PV available. Otherwise it would probably wear out the contactors quickly if it hovered right at 85%, charging for a few minutes then stopping.
