This product works as intended. However. It has a design flaw. When this device is connected, everything works fine. If the inverter fails, however, there is no security. You need to add a relay to the system so that the inverter will cut the 12v line and switch to shore power if something happens to the inverter. System as designed - if the inverter fails, the automatic switch is still connected to the battery, and if the battery is still at a certain voltage, the automatic switch will not switch and will not continue to power any device connected to it. Now, with a relay in the system, if something happens to the inverter, the relay will break the 12V line, causing the switcher to switch to shore power. I hope this helps someone, I will link the devices I use and attach photos. https://www.amazon.com/MAGNECRAFT-725BXXSC3ML-120A-POWER-DPST-NO-120VAC/dp/B00DDEEZCE/ref=sr_1_1?dchild=1&keywords=725BXXSC3ML-120A&qid=1586289526&sr=8-1 although you can get cheaper elsewhere.
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