Can I make an uninterruptible power supply for my furnace?
So, last winter, my area got TONS of snow, very cold temperatures ( I spent 20 minutes dropping droplets of water on an iron railing and literally watching it freeze), and then we lost power. Our furnace runs on natural gas, so it would've worked, except that the fan inside it and also the ignition system (I'm pretty sure) wouldn't work without power. I'm thinking of getting maybe 10 or so surplus marine/car 12 volt batteries and a high-power inverter, and running the furnace off normal 120 AC, until power goes out, then a relay ( or some solid-state circuitry) would trigger the batteries ( in parallel), which would charge either off of a solar panel outside, or wall power once the power was back on. Also, the furnace has what looks to be a pretty basic motherboard inside of it, would I need an inverter that makes a really sine-y sine wave for that, or could I get away with a cheap square wave one? Also, it's wired directly into its own circuit, though I'm pretty sure it's still 120 V. Comments, advice, etc. is welcome. Thanks!