Something you want to consider is if you parallel a remote switch with the internal switch both switches need to be off for the unit to be off. If either switch is On the unit will be on. But you can't for example, remotely turn the inverter On and use the switch on the inverter to turn it off as whichever switch you turn it on with needs to be the switch to turn it off.

Your picture shows a 500 watt inverter so if delivering full power of 500 watts discounting inefficiency of the inverter tells me under full 500 watt load the inverter will draw 500 Watts / 12 Volts = close to 42 Amps or a 500 watt surge 300 watt standard out will be 300 watts / 12 volts = 25 Amps so the wire gauge needs to be planned accordingly. My guess is the small switch pictured will not come close to those DC current ratings. The switch on the inverter is not handling the inverter load but merely turning electronics in the inverter. Purely a guess on my part.

As to the switch and mentioned earlier, a switch is merely a switch. The contacts may be rated in AC or DC but your concern is how much current are you switching. The rated contact voltage and current, beyond that it's just a switch.

Ron

 

I would think the switch is enabling the inverter, not switching the 12V power.
Are the original switch wires the same size as those that go to the battery, or smaller. That is a clue.

 

The receiver circuitry in the switch might be expecting a particle voltage to function.

 

Yeah, the switch just turns on the inverter. The inverter is feed by 8 gauge stranded copper.

Yes, the circuitry is expecting a particular voltage. It's not just a simple switch. The remote needs to be paired with the receiver and it can't do that without 120V. I was able to pair it with 120V then install the switch but it still doesn't work.

DC remote switch will be installed tomorrow.

 

I did a remote switch for an inverter some time ago, and it had 3 wires. 0V, +12V supplied from the inverter, and a switched voltage back to the inverter. Unfortunatly, I cannot remember what it used. So you will need to try to trace the switch on circuit. It may be a voltage divider across the 12V supply ans the center point fed back?
A Google may help.

 

The item that you are asking about is incorrectly called a "switch", whereas it is actually a remote controlled power relay of some kind. That is where your problem lies. That much is obvious from the picture in the very first posting. The fact that it is shown switching a AC line, and having an AC power connection, both line and neutral, tell us that it is not suitable for switching the power for a DC to AC inverter. It might be possible to surgically modify the device to suit your application but I doubt that it would be simple or easy to do. So you need a different piece of equipment, one designed to use 12 volts DC as the power control source. But any such device will be drawing some current all the time, because it is constantly waiting for an instruction. This means that the battery charge will not last as long.