Normal AA/AAA batteries that have a voltage rating of 1.5V can supply constant 50mA current for a total capacity of 1800-2600 mAh charge and 3.90Wh of energy- Alkaline batteries.
Now theoretically, if the battery is assumed to be ideal, then it can supply a current of 1A if the resistance across it is 1.5 ohms(I = V/R = 1.5V/1.5 ohms = 1A). So the power consumed is 1.5W and so, it can supply this power for at least 2 hours(t = Energy/Power = 3.9Wh/1.5W = 2.6 hours).This calculation is applicable only when the voltage and current are constant. practically impossible.
However, things are not always ideal and the internal resistance of the cell plays a detrimental role here. So, the maximum current capacity can be ascertained by measuring the short circuit current. For a good quality battery, it may range anywhere from 4-7 A which won’t last for more than a few minutes or so.
Having said that, there is still no clear explanation as to how long can the cell provide the constant current because of the high discharge rate. Any current of more than 0.5A drawn from the cell reduces the voltage considerably and then you see, all the calculation goes in vain. The best way to calculate the time is only via experimentation because standard results are not acceptable here
