Option to block discharge but keep offgrid fallback

@laserranger
I haven’t tested whether it switches toninverting or not bu the passthrough state will probably achieve what you want. I am sure it will swirch to inverting though. Or at least logic would suggest that.

It stops charge from grid and discharge to loads in this state.

As a further thought you could just freeze the soc 1or2% behind the actual SoC to prevent charge from grid.