9:25 Since the transformer is basically just a big inductor, I'd guess it is kind of storing a bit of current in the windings on each 60hz cycle? So when you turn on the compressor and the in-rush current spikes, it takes energy from the transformer first and softens the load on the inverter so it has a millisecond or two to catch up. Could be why the compressor seems to have more "ooomf." Also with that autotransformer you could certainly pull that thing out and run your Inverter's 240v L and N (which could act as L1 and L2) wires to it and you would get a Neutral out of that third leg from the transformer, you could then run all 3 wires an ordinary breaker panel creating a split-phase system. However I'm not sure what the rules are for grounding and safety when also having the inverter charging off the grid, I'm from Australia but I find your split phase system fascinating, keep up the good work!
Physically they are the tough round cells. Vs the fragile pouch type. I guess if they go they go. But some battery needs I know recommended there when they became available. And I'm using them under their rating is current and I'm total charge voltage. Leaving a buffer. The compressor in my DIY heat pump for the water heater is small so the inverter has more than enough. So did the other one but the other one had a weird artifact on the output. I could hear it in transformers plugged into it (audio amps etc). May have been hurt from the initial abuse of running two capacitor start compressors on it in is early life.
I own a bunch of those amazon autotransformers, both the 2:1 and the 1.2/1.1:1 (japan voltage conversion ). They are a good buy , but beware that the switches they usually come with are utter garbage and will e first thing to burn up when you push ''em hard. The circuit breaker switches are fine but it's those DPDT selector switches that are typical sh!te chineseum fake-rated with high resistance steel contacts and soft, melty thermoplastic instead of bakelite or decent glass fiber reinforced thermoplastic . I either changed out the switch for US gardner bender switch or (in most cases) just hardwired the configuration i was using and delete the switch .
I looked at the split phase/3 phase capable ones. To do a split phase you need a MINIMUM of two of these inverters. For the 3 phase setup you need 3 of them. It isn't split phase out of the single inverter. At least not in this line and price range. I almost clicked on ADD TO CART but then glad I took another look. The one that can do split phase built in is twice the price. I just got it knowing I might run my ductless off of it. I didn't plan on running the house off of it etc