We assume the following:
Using 12V system.
CoolFocus operation hours: 7 hours
Inverter efficiency: 85% (Good quality modified sine wave inverter)
Depth of discharge: 95% (Lithium deep-cycle battery)
Constant power demand = 300W.
With a 12V battery, the current will be 300 / 12V = 25 Amp (Make sure the wire you use can carry 25A constant current).
Peak power demand is about 1800W for 5-15 milliseconds.
1800 / 12V = 150 Amp ( Make sure your battery has a CCA rating equal or higher than 150 Amp)
The battery size can be roughly estimated with the following equation:
(duration x steady battery current) / (depth of discharge * inverter efficiency)
Based on the above figures, the equation gives:
(7 hours x 25 Amp ) / ( 0.95 depth discharge x 0.85 inverter efficiency ) = 216.7 Amp-hours
Round it up to 220Ah. This is the smallest battery size it requires to run the AC for 7 hours. Please note that the Coolzy when used with the Igloo tent has the potential to extend the operation time by about 30% under certain and remote control settings.
Please also allow extra capacity for other appliances that could possibly consuming power at the same time.