How can I convert 120 Volts DC into 120 Volts AC?

mrcshbs2002 asked: This is for a project I am working on. I need to run an small air compressor (120V - 15 amps). I know I could use a power inverter that converter 12V to 120V etc, but my friend said since I already have a 10 battery bank, I could build a 120DC to [...]