I have a DJ-580T and occasionally I will use a 12V 6AH Power Pack for day events - and I was wondering the power consumption of a 5 Watt transmission.  How much is being drawn from a battery in - let's say a 2 minute transmission @ 5 Watts.  I find that the NiCads that came with the HT are not sufficient for such an event - and go through 2, 12V 1200mAH packs while I also feel this 6AH battery is overkill since I could use it again without recharging it.

   Could someone with some technical knowledge of this give me an idea of the power consumption of a 5Watt  transmission.  And a way to guage this so that I don't have to lug this pack around with me - maybe I'll be able to build a smaller pack for myself for the future.   
   Sorry if this vague in any way - I have no idea how to put this.

Thanks in advance