Help understanding 12v 0.09amp Fans etc.

[nativepaul]

you could use the .58Amp one direct of 7.2 like you tried, it will draw .58Ax7.2V/12V=.348Amps, that would take 4.2AH/.348A=12hours to flatten a 4200mah pack you would be hard pushed to notice a difference in runtime, if you get 10min runs at the moment that's 4.2AHx60=252AmpMinutes /10Minutes=25.2Amps average, add .348A for the fan and it would go down to 25.2A+.348A=25.548A, 252AmpMinutes/25.548A=9.86 Minutes.

EDIT: everyone else beat me to it while I was doing the maths, but hopefully the equasions will be of some help to you working out amp draws or runtimes in the future.