I have a small cabin with a L14-30 inlet box, which feeds a 30 amp breaker in the cabin . Recently purcased 200 watts of solar panels that feed a 12 volt battery bank. I have a 120 volt inverter, how do I connect 120 volt plug to a L14-30 plug.

That was probably for a generator. And is a 120/240 setup. Is the cabin wired for 120VAC? Since you are off the grid, the simplest thing to do is run the inverter output into the breaker box, swap out the 30 for a 15. About the most you can run with the inverter are lights and maybe a very small appliance-radio etc.

At only 200 watts I would not even bother with it.

That was probably for a generator. and is a 120/240 setup. Is the cabin wired for 120VAC? Since you are off the grid, the simplest thing to do is run the inverter output into the breaker box, swap out the 30 for a 15. About the most you can run with the inverter are lights and maybe a very small appliance-radio etc.

The inside breaker box has the 30amp breaker and two 15 amp breakers, each 15 amp breaker has 5 outlets on it. The solar panels (10 Amp output midday) powers a 13" TV, computer, and directv box ( 4.8 Amps). It also stores energy in a 400 amp hr. battery bank. The cabin does not have a kitchen or any large appliances. I use a extension cord from a 3000 watt inverter into a power strip to run TV and directv box. Would like to be able to use outlets upstairs and downstairs throughout the cabin ( 750 square feet)

When you open the plug, the wire going to the notched spade is the ground straight above or below depending on how you are holding it is the common, 90 degrees from the notched spade on both sides is the hot wires one is connected to one side and the other is connected to the other side of your circuit box. Your inverter cannot run both sides you will need another you can run them in tandem but only one per side. If you try to draw from one outlet you can still overload the inverter. The trick is distributing the load between the two IE don't put everything on one circuit and don't turn everything on at once. How many batteries are in your bank? From your post you can't run this more than a few hours, Math says 1.8hrs at nominal charge.

" It also stores energy in a 400 amp hr. battery bank." How many batteries? AT 12 volts, not 120VAC. At 3000watts and 120VAC, you are talking a maxed out 25 amps. You will be able to draw some power but if it clouds up and at night, you will lose power quickly as you will deplete the batteries depending on what you are running. Can you wire outlets? Sure but be aware that breaker panels are designed for 240 VAC so you will not have the panel wired properly if you feed 120VAC.

" It also stores energy in a 400 amp hr. battery bank." How many batteries? AT 12 volts, not 120VAC. At 3000watts and 120VAC, you are talking a maxed out 25 amps. You will be able to draw some power but if it clouds up and at night, you will lose power quickly as you will deplete the batteries depending on what you are running. Can you wire outlets? Sure but be aware that breaker panels are designed for 240 VAC so you will not have the panel wired properly if you feed 120VAC.

I still use the generator when necessary. Is their any way to convert from 3 prong 120 to RV to L14-30 Plug. I will not have any large draws in the cabin. I heard somewhere this will make the ground in the two 15 amp circuits to become hot if there is a large draw.