This video shows the dangers of "number 10 wire" ingenuity at your home during an extended power outage, such as after an earthquake.
It's very good at telling you what your should NOT do with a bank of 12V batteries and a cheap inverter, lest you destroy appliances, set your house on fire or electrocute someone.
Those Americans preppers might be crazy, but some do know how to jury rig.
"How NOT to Connect an Inverter to Your House Mains"