The user manual is completely unclear on this, so I asked Giandel support. This is their response:
The inverter PS-2200KSC has a built-in solar controller, if you use the built-in controller, the battery switch should be set to GEL if use Lithium battery.
If you don't use its built-in...
I bought a GIANDEL 2200W Pure Sine Wave Power Inverter but thought the solar inputs were a terminal block. The inverter will be mounted where it's not easily accessed so I want a regular outlet elsewhere in the camper. Is it safe/OK to run two extension cords to two single standard outlets?
Thank you. That was my question. This inverter has inputs for solar panels, and they look similar to a terminal block, which is what I was planning to use.