Gut check on transfer switch for inverter - special case

[thedavidzoo]

A few years back we DIY installed our current lithium/solar system which is charged only through roof solar. We initially rewired a few 110V outlets dedicated to the inverter, including the microwave. We "never" plug into shore, do not have a generator, and do not charge the batteries via truck (disabled with switch at converter just in case). The generator compartment is prewired into an existing automatic transfer switch (shore or generator). Converter is standard dealer WFCO type.

We are now relooking all our outlets and USB charging ports to make them a little more logical for our uses. We would like to again rewire so that all 110V outlets run from the inverter. I hear that you do not want a loop where the inverter draws on the batteries, feeds back into the converter (using an automatic or manual transfer switch), and charges the batteries.

Now our system is a little different, I think. Our lithiums have individual cell BMS and an integrated battery control system "computer" (the brain) which regulates all battery in and out power among other things. We have no direct positive connection between converter and battery as would be the usual way. Any charging source (only solar now) comes through the C+ connection on the brain. All loads (to inverter, converter) go out through L+ on the brain. Therefore, I conclude that there is no way the converter can feed back into the batteries with the inverter powering the converter. Confused yet?

Plus, I think I can just wire the green manual transfer switch after the existing one so I can select the inverter or shore.

Also, our fridge is 110/12V compressor. I think I could just unplug its 110v cord and force it to run 12V when the inverter is on.
Wouldn't affect the furnace, only 12V.
Would only affect propane WH for initial spark? Wouldn't use electric WH on inverter anyway.
Wouldn't try to use AC air on inverter either, might have to rig thermostat switch against accidental bumps.

So many questions. My sketch, don't laugh. Thanks.

[Hemi_Joel]

I didn't think you could run 2 solar charge controllers in parallel? Doesn't one sense the output of the other and interpret that as a fully charged battery, cutting 1/2 your solar array out?

[time2roll]

Since it looks like you are using the WFCO 120v/12v distribution panel I am fairly certain if you power up the 120v side of the panel the converter will put 13.6 volts onto the DC side. Something will need to be disconnected to disable the converter.

Not sure why you would not just feed the generator side of the OEM transfer switch.

If you want to power just the outlets you can get a small transfer switch to power just the branch circuit(s) with outlets. Although sometimes the branch circuit that feeds the outlets also feeds the converter and fridge. Adjustments for that would have to be made.

[2oldman]

I'll try.

First, I don't see any converter in your schematic. Perhaps I don't know what an IBC is.

If you "never" (not sure what that means) plug in, and don't have a generator, how could you power a converter?

Running the entire house on inverter is a nice way to go, but you may be tempted to run large appliances like toaster and MW. If so, I suggest you up your battery voltage (and inverter) to at least 24v. Gets rid of the fat wire.

I don't know why you have 2 solar controllers. You could series your panels, get rid of the combiners and more fat wire, and just have one.