Better?
Batteries: 800mA @ 5.12V = 4.096W
Load: 240mA @ 12V = 2.88W
Module consumes 1.216W
Not very efficient.
Total power of the "batteries in perfect world" @ 5.12V = 10.24W
Shouldn't drain your batteries more then 50% or 5.12W of power to safely use.