snipped story about inverters for emergency lighting

You might find it helpful to look about RV supply places. There are a
number of (often somewhat spendy, unfortunately) inverter/charger units
available that do it all automatically and have decent sine wave
outputs. Basically, they just hook up to the AC input, battery, and
output, and will charge the battery as needed when AC is around and
automatically switch over to inverter mode when AC is
removed--essentially a UPS circuit, really. I'd trust them to work
reliably in an emergency more than I'd trust a cheap no-name inverter.

--
Andrew Erickson

"He is no fool who gives what he cannot keep to gain that which he cannot
lose." -- Jim Elliot