I find stuff, then I try to use it.

Maybe a terrible subject line.

Anyway, I'm a step away from being a horder but cool stuff finds me and I get it for free or cheap. As a result, I have a half dozen Northstar 170Ah deep cycle sealed batteries (12v) (they've been sitting on a battery maintainer for a few years), and a 20kWh Onan diesel genset (208v 3 phase). My house in the woods is near the end of a long run single wire grid connection with a 100A service. Due to distance from infrastructure, the line goes down a lot and/or browns out a lot. The transformer on the pole gives me a split-phase 240. I'm also collecting 18650's for later use.

I have lots of SW facing roof space so I plan to start looking for some PV cells at some point.

My current problem is the generator. I don't really know what to do with 3 phase 208v. I know I can run 208v split phase out of it by connecting to two of the poles and get a subset of rated output. But it seems to me the obvious answer is to find an inverter that can accept split-phase 240VAC from the grid and 3 phase 208 from my genset as well as provide an MPPT charger from eventual panels.

I was looking at mppsolar (since a lot of the posts on here are referencing their inverters) and I'm having trouble understanding whether any of their inverters will accept both 240VAC and 208VAC inputs.

Am I looking for a unicorn or is what I want simple?

I don't think what you're looking for exists. I was thinking you could use a rotary phase converter but there might not be a need if the only job of the generator would be to charge your batteries. You could get 3 isolated output chargers, one on each phase to balance the load. Then get a separate charger/inverter for the single phase system.

That's actually not a terrible idea. It's certainly a way to utilize the genset to some extent.

Thanks.