You can use 120VAC input on only one inverter (of a split phase system) to charge the batteries if the following steps are taken:
The 1ph 120V must go into the L1 unit for this to work.
If it is already set up for split-phase, use the VE.Bus System Configurator program and “Get Configuration”
Then uncheck the “Switch as Group” box. Green circle around L1 and L2 boxes will go away.
This allows L1 to accept 120V while L2 stays in inverter mode.
If this has not been programmed for split-phase yet, do that first and then uncheck the Switch as Group